Age-related changes in lipid and carbohydrate metabolism of the genetically obese mouse

Obese mice (C57BL/6J ob/ob) and their lean controls were studied longitudinally from immediately post-weaning until 62 wk of age, at which time the experiment was terminated. The dynamic nature of the metabolic aberrations of the obese mouse syndrome was clearly demonstrated. Obese mice were hyperinsulinemic at all ages yet the concentration of glucose in plasma was elevated only at 5-20 wk and 63 wk of age, but was similar to that of lean mice at 20-60 wk of age. Triacylglycerols accumulated in the liver of obese mice between 5 and 18 wk of age to a level that was 20-fold greater than that found in the age-matched lean control. A decreased concentration of DNA/g of liver was also found in 5-18 wk-old obese mice, indicative of an enlarged hepatocyte. With the exception of 5-wk-old animals, total DNA per liver was increased in obese mice when compared to the lean control throughout the profile. Following the peak in 18-wk-old mice, the hepatic content of triacylglycerols precipitously fell so that at 45 wk of age its concentration in obese mice was similar to that of the lean control. Plasma free fatty acid levels as well as liver glycogen content were comparable in obese mice and their lean controls throughout the profile. In obese mice older than 45 wk of age, the content of triacylglycerols in plasma was significantly lower than that of the age-matched lean control while an accumulation of liver triacylglycerols was again found in obese mice. Myocardial triacylglycerols were elevated in obese mice when compared to the lean control at all ages. The longitudinal metabolic profile of the obese mouse developed in the present study clearly demonstrates the dynamic nature of the deviations in carbohydrate and lipid metabolism in this animal model of human obesity and insulin resistance.     

Relationship of body fat topography to insulin sensitivity and metabolic profiles in premenopausal women

The relationship of body fat distribution to metabolic profiles was determined in 80 healthy premenopausal white women of a wide range of obesity levels [percentage of ideal body weight (% IBW) 92-251]. Distribution of fat between the upper and lower body was assessed from the waist/hips girth ratio (WHR), which varied from 0.64 to 1.02. In 23 women, in vivo insulin sensitivity was also determined from the steady-state plasma glucose (SSPG) level at comparable insulin levels of approximately 100 microU/mL attained by the intravenous infusion of somatostatin, glucose, and insulin. Increasing WHR was accompanied by progressively increasing fasting plasma insulin levels (r = 0.47, P less than 0.001), insulin and glucose areas after glucose challenge (r = 0.53, P less than 0.001; r = 0.50, P less than 0.001, respectively) and fasting plasma triglyceride concentrations (r = 0.48, P less than 0.001). Obesity level was similarly correlated with these metabolic indices. Partial and multiple regression analysis and analysis of variance with a linear contrast model revealed that the effects of body fat topography were independent of, and additive to, those of obesity level. Within obese subjects alone (%IBW: 130), %IBW had no predictive value, but WHR remained a significant predictor of plasma glucose, insulin, and triglyceride concentrations. The WHR also correlated with the plasma cholesterol level, but this association was largely dependent on its relationship to %IBW. Both WHR and %IBW correlated with the insulin resistance index, SSPG (r = 0.60, P less than 0.01; r = 0.61, P less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of propranolol and nitroglycerin plus methoxamine on transmural creatine kinase activity after acute coronary occlusion.

Transmural creatine kinase activity was determined 5 hours after acute occlusion of the left anterior descending coronary artery in 27 open chest anesthetized dogs. In seven dogs, propranolol, 2 mg/kg, was given intravenously over a 10 minute period 10 minutes after occlusion. In 10 dogs, nitroglycerin, 300 microgram/min, was infused intravenously for 1 hour 10 minutes after occlusion. Methoxamine, 300 to 500 microgram, was administered to return blood pressure and heart rate to prenitroglycerin levels. In untreated dogs, there was a distinct transmural gradient of creatine kinase activity in the ischemic region from subepicardium to subendocardium: nonischemic subepicardium 1,187 +/- 50 international units (IU)/g versus ischemic subepicardium 1,054 +/- 46 IU/g and nonischemic subendocardium 1,170 +/- 53 IU/g versus ischemic subendocard;um 766 +/- 42 IU/g, respectively. Administration of propranolol did not affect the transmural creatine kinase gradient after 5 hours of occlusion. In contrast, nitroglycerin plus methoxamine significantly (P less than 0.05) decreased subendocardial creatine kinase depletion after 5 hours of occlusion (776 +/- 42 versus 978 +/- 47 IU/g). These findings demonstrate the unique capability of nitroglycerin plus methoxamine to protect the subendocardium during ischemic insult.     

Redistribution of myocardial blood flow distal to a dynamic coronary arterial stenosis by sympathomimetic amines: Comparison of dopamine,dobutamine and isoproterenol

The effects of dopamine, dobutamine and isoproterenol on coronary hemodynamics, severity of stenosis, distal bed resistance and transmural myocardial perfusion gradients with radioactive microspheres were studied in dogs with a mild obstruction of the left circumflex coronary artery anesthetized with morphine-chloralose. Changes in transmural blood flow were related to the ratio of the diastolic aortic pressure-time Index to tension-time index (DPTI/TTI) and the ratio of the distal diastolic coronary pressure-time index to tension-time index (DDPT1/TTI). At doses of 5 gmg/kg per min, dopamine had no significant effect on DPTI/TTI, DDPTI/TTI or endocardial/epicardial flow ratio; however, dobutamine produced a slight decrease in this flow ratio and in DDPTI/TTI. At doses of 10 gmg/kg per min, both drugs produced a significant (p <0.05) reduction in diastolic coronary pressure distal to the stenosis, DDPTI/TTI and endocardial/epicardial flow ratio without change in DPTI/TTI. In comparison, isoproterenol (0.01 and 0.05 gmg/kg per min) produced dose-related decreases in endocardial/epicardial flow ratio, DDPTI/TTI and DPTI/TTI. During infusion of each sympathomimetic agent, there was a corresponding reduction in distal bed vascular resistance but a concomitant increase in stenosis resistance.The results also show that dopamine and dobutamine, as well as isoproterenol, are capable of producing a maldistribution of coronary blood flow distal to a mild coronary arterial stenosis and that such a redistribution of flow is dependent on dose, reduction of the distal diastolic coronary pressure-time index and decrease in DDPTI/TTI. It Is further concluded that hemodynamic changes distal to a coronary arterial stenosis seriously jeopardize the usefulness of DPTI/TTI; however, DDPTI/TTI can be used to predict drug effects on the endocardial/epicardial flow ratio in an ischemie area. This study demonstrates that “fixed” stenoses can undergo dynamic processes and sympathomlmetic amines increase the resistance to flow through a stenotic coronary artery in the nonfailing heart.     

Comparative effects of cardioselective versus noncardioselective beta blockade on subendocardial blood flow and contractile function in ischemic myocardium.

The comparative effects of three beta adrenergic antagonists, bevantolol (CI-775, a new cardioselective agent), practolol and propranolol, on regional myocardial blood flow and contractile function distal to a severe flow-limiting stenosis of the left circumflex coronary artery were studied in the anesthetized dog. Equivalent beta₁ receptor blocking doses of each agent were administered 30 minutes after production of a stenosis sufficient to reduce resting coronary blood flow and contractile force approximately 40 percent. Regional myocardial blood flow and contractile force were measured with radioactive labeled microspheres and Brodie-Walton strain gauge arches, respectively. After treatment with propranolol (0.3 mg/kg), subepicardial flow in the ischemic area decreased significantly whereas subendocardial flow was maintained, resulting in an increased endocardial/epicardial blood flow ratio (0.59 ± 0.05 to 0.93 ± 0.09) (mean ± standard error of the mean). No significant change was observed in contractile performance of the ischemic area. Practolol (1.0 mg/kg) also produced a significant increase in endocardial/epicardial ratio (0.59 ± 0.05 to 0.69 ± 0.10) in the ischemic myocardium. Contractile performance remained unchanged. In contrast, after treatment with bevantolol (1.0 mg/kg), subendocardial flow (0.64 ± 0.13 to 0.77 ± 0.13 ml/min per g) and contractile function increased significantly (36.0 ± 11.0 percent) in ischemic myocardium. A marked increase in endocardial/ epicardial ratio (0.59 ± 0.05 to 0.93 ± 0.09) was also observed.These results suggest that a redistribution of blood flow within an ischemic region of the myocardium occurs with either beta₁ or a simultaneous beta₁ and beta₂ receptor blockade. Furthermore, these data indicate a possible advantage of a new cardioselective beta adrenergic antagonist, bevantolol, in improving ischemic subendocardial blood flow and contractile function.     

Coronary steal-induced increase in myocardial infarct size after pharmacologic coronary vasodilation

This study was performed to determine if maximal coronary arterial vasodilation of nonischemlc areas would produce an increase in myocardial infarct size through a “steal” of collateral flow from an ischemic region. Myocardial infarction was produced by a 2 hour occlusion and reperfusion of the distal left anterior descending coronary artery in anesthetized dogs. Five minutes after occlusion, 7 dogs were given saline solution, and in 12 dogs the coronary vasodilator chromonar (8 mg/kg, intravenously) was administered. Chromonar produced a significant Increase (p < 0.05) in blood flow to nonischemic regions and a concomitant decrease in flow to ischemic areas. Associated with these changes in flow was an elevation in total release and peak plasma creatine kinase compared with values in saline-treated control dogs. Myocardial infarct size determined with nitroblue tetrazolium staining was significantly increased (p < 0.05). These data demonstrate that maximal coronary vasodilation of nonischemic areas can result in an extension of myocardial infarction by a steal of collateral flow away from the ischemic region.     

Coronary steal in four models of single or multiple vessel obstruction in dogs

Two types of coronary steal (subendocardial to subepicardial; collateral dependent to noncollateral dependent) were examined in four models of single or multiple vessel obstruction In 32 anesthetized dogs with controlled heart rate and aortic blood pressure. Different degrees of vasodilation were produced by use of the selective coronary arteriolar dilator, chromonar. Subendocardial to subepicardial steal was studied in two models of stenosis, mild (50 percent decrease in reactive hyperemia) and severe (93 percent decrease In reactive hyperemia). During mild left circumflex arterial stenosis, chromonar produced an Increase In poststenotic blood flow primarily In the subeptoardtum with only minimal increases in the subendocardium. The Ischemic $\text{endocardial}\text{epicardial}$ flow ratio decreased significantly. During severe left circumflex stenosis, chromonar produced an increase in poststenotic subepicardial flow whereas subendocardial flow decreased. The ischemic $\text{endocardial}\text{epicardial}$ flow ratio also decreased significantly. Changes In $\text{endocardial}\text{epicardial}$ flow ratio correlated closely with distal diastolic perfusion pressure in both models of stenosis (r = 0.84, p <0.001).Collateral-dependent to noncollateral-dependent steal was studied in two models of total left anterior descending coronary arterial occlusion. During distal occlusion of this artery, collateral blood flow decreased significantly only during chromonar-lnduced maximal vasodilation, whereas mild vasodilation produced a significant decrease in collateral flow when a proximal left circumflex stenosis was present in addition to occlusion of the left anterior descending artery. These results demonstrate that mild to maximal coronary vasodilation produces coronary steal in different models of single or multiple vessel disease In the absence of changes in aortic pressure and heart rate. Decreases in perfusion pressure distal to a stenosis or at the origin of collateral vessels are responsible for the two types of coronary steal.     

Coronary hemodynamics and subendocardial perfusion distal to stenoses

We compared distal coronary hemodynamics and regional myocardial perfusion in anesthetized dogs in the presence of a single or two coronary artery stenoses in series. After application of either a single or two stenoses on the left anterior descending coronary artery, regional myocardial blood flow was measured with radioactive microspheres. Moderate degrees of single-vessel stenosis (no change in resting coronary blood flow but reduction in reactive hyperemic response of 70%) resulted in no significant change in regional myocardial perfusion at rest despite a pressure drop across the stenosis of 24 +/- 3 mm Hg. When two such stenoses were applied in series, there was a 91% decrease in reactive hyperemia, a significant reduction in resting diastolic coronary blood flow and a 51 +/- 7 mm Hg pressure drop across the two stenoses. Alone, each stenosis produced no change in regional myocardial perfusion; however, together the two stenoses resulted in a significant decrease in subendocardial blood flow and a redistribution of transmural perfusion within the ischemic zone favoring the subepicardium (endo/epi from 0.95 +/- 0.03 to 0.72 +/- 0.03). The results indicate that whereas resting subendocardial perfusion is not significantly affected by moderate degrees of a single coronary artery stenosis, multiple stenoses of the same severity may dramatically reduce subendocardial perfusion.     

Nonenzymatic glycosylation of human plasma low density lipoprotein. Evidence for in vitro and in vivo glucosylation

To determine the effect of persistent hyperglycemia on the structure of the plasma low density lipoproteins (LDL), nonenzymatic glycosylation of human LDL was studied by incubating LDL isolated from normal subjects with 5 mM or 15 mM glucose in a sterile, buffered solution of pH 7.0 or 9.0, at 4°C, 23°C, or 37°C under nitrogen. The aliquots taken at different intervals showed that the glucose incorporation rate was linear up to the 5th day and was dependent upon pH. The glucose was not incorporated into the lipid portion of the LDL. When the LDL was chemically modified with group specific reagents (diketene for lysyl residues, and cyclohexanedione for arginyl residues), the LDL with modified lysyl residues incorporated glucose much less than untreated LDL, whereas the LDL modified with cyclohexanedione was glycosylated more than the control, suggesting that the lysyl residues are the primary reaction sites. When the amino acids of acid hydrolysates were analyzed by ion exchange chromatography, the radioactivities of either the LDL incubated with glucose and sodium [³H-] borohydride, or the LDL reacted with [U-¹⁴C] glucose and sodium borohydride were found in glucosyllysine. The nonenzymatic glucosylation of LDL was also determined with purified LDLs from 6 normal and 6 overtly diabetic subjects. Incorporation of tritium from borohydride, delipidation, acid hydrolysis and chromatography gave radioactivity peaks identified as glycosyllysine. These results suggest that lysyl residues in human plasma LDL can be glycosylated in vivo and in vitro not only in diabetics, but also in normal subjects. The ?-amino groups of the lysyl residues on or near the surface of LDL, an important residue controlling its interaction with the LDL receptor(s), are the primary reactive sites. This interaction between plasma glucose and plasma LDL may have relevance in LDL metabolism in diabetic subjects.     

Integrated regulation of very low density lipoprotein triglyceride and apolipoprotein-B kinetics in man: Normolipemic subjects,familial hypertriglyceridemia and familial combined hyperlipidemia

Turnover kinetics of triglycerides (TG) and apolipoprotein-B (apo-B) of plasma very low density lipoprotein (VLDL) and their relationship to plasma VLDL composition and VLDL apo-B conversion to low density lipoprotein (LDL) were determined in age and weight-matched groups of normolipemic (NL) healthy subjects, patients with familial combined hyperlipidemia (FCHL) and patients with familial hypertriglyceridemia (FHTG). In NL subjects, a significant correlation as observed between VLDL TG or VLDL apo-B turnover rate and its circulating mass, suggesting that the plasma level of VLDL was determined by the secretion rate of VLDL TG and apo-B. The positive significant correlation between VLDL TG and apo-B also suggests that the production of these moieties was integrated at the synthetic and/or secretory sites to maintain the ratio of TG to apo-B in plasma VLDL. In moderately obese NL subjects, proportionate increases in VLDL TG and apo-B turnover rates resulted in enhanced secretion of VLDL particles. Both groups with genetic hypertriglyceridemia had increased VLDL TG and VLDL apo-B turnover rates. This increase accounted for the increase in circulating VLDL TG and apo-B mass. In patients with FCHL, turnover rates of VLDL TG and apo-B were equally increased, hence, the ratios between major VLDL constituents were within normal limits. On the other hand, the increase in VLDL TG turnover in patients with FHTG was disproportionately greater than that of apo-B resulting in a higher ratio of TG to other VLDL components. In NL subjects, approximately 72% of VLDL apo-B released into plasma was converted to LDL. This conversion correlated positively with VLDL apo-B turnover rate and inversely with VLDL TG turnover rate. Formation of LDL from VLDL was significantly greater in the obese individuals. In FCHL, conversion of VLDL to LDL represented the major pathway for VLDL apo-B catabolism. The increased VLDL apo-B load was predominantly catabolized to LDL. The greater increase in VLDL TG turnover relative to apo-B in FHTG, on the other hand, resulted in a smaller fraction of VLDL apo-B recovered in LDL, most of the VLDL apo-B being removed via a pathway that did not involve this conversion. We conclude that the composition and metabolic fate of plasma VLDL may be greatly influenced by the secretion rates of VLDL TG and apo-B. If VLDL conversion to LDL and the subsequent catabolism of the latter provides a major route for delivery of cholesterol ester to peripheral tissues, then the increased LDL production in FCHL compared to FHTG may account for a higher cardiovascular risk.     

Changes in lipoprotein composition during the menstrual cycle.

Composition of major plasma lipoproteins was studied in 14 normal women during different phases of the menstrual cycle for three consecutive months. The results were compared to measurements in ten normal age-matched men for a comparable period, to delineate possible sex differences in lipoprotein metabolism in young adults. Blood samples were obtained every 3--5 days after a 14-hr overnight fast and processed for determinations of total plasma cholesterol, LDL- and HDL-cholesterol, and apoproteins B and A-1. In premenopausal women, a significant, 10%--25% cyclical suppression of total plasma cholesterol, LDL-Chol, and LDL-apoB occurred during the luteal phase, which was significantly lower than unchanging concentrations found in men at any time interval. HDL-Chol remained in a significantly higher fixed concentration range in the female subjects as compared to the men. These sex differences in lipoprotein metabolism may have relevance to the reduced susceptibility of premenopausal women to atherosclerosis.     

Altered apolipoproteins in sex steroid-treated rats.

Effects of sex steroid treatment on plasma triglycerides (TG) were studied in relation to altered plasma lipoprotein composition, plasma postheparin lipolytic activity (PHLA), tissue lipoprotein lipase (LPL), and apoprotein C (apoC) composition and turnover. Adult female rats received parenteral estradiol benzoate (E, 5 μg daily), progesterone (P, 5 mg daily), or the two in combination (E+P) for 21 days. Control rats were administered the sesame oil vehicle alone. E or E+P treatments induced hypertriglyceridemia. Plasma TG, very low density lipoportein (VLDL)-TG, VLDL-protein and high-density lipoprotein (HDL)-protein content were significantly increased 25%–100% compared to control animals. The P regimen alone was without effect on these parameters. While total plasma cholesterol was unchanged by these treatment regimens, HDL-cholesterol was significantly increased in E or E+P groups. Increased plasma TG in E or E+P groups was associated with depressed total PHLA and protamine-sensitive PHLA. However, when parameterial adipose tissue from these animals was incubated with glucose, amino acids, and heparin, release of LPL in the E group was decreased, whereas in E+P it was increased. P treatment resulted in augmentation of both PHLA and LPL activity. Thus, a discrepancy existed between PHLA and LPL release only in the E+P group. When serum from E or E+P groups was added to an LPL assay system using control male rat adipose tissue, LPL activity was suppresed 50%–200% with increasing amounts of serum. In addition, serum from these groups significantly reduced recovery of exogenous PHLA enzyme added to normal rat chylomicrons in vitro, suggesting impaired binding of heparin-releasable enzyme to lipid substrate as one possibility. The inhibitory factor was unrelated to the concentration or lipoprotein form of TG in serum. Apoproteins of VLDL and HDL fractionated by polyacrylamide gel electrophoresis showed increased apoC, arginine-rich peptides, and apoAI in E and E+P rats. Since human apoCII is an activator of LPL and apoCIII is an inhibitor, comparable fractions of rat sera were quantitated from VLDL and HDL following delipidation with tetramethylurea and polyacrylamide gel electrophoresis. Utilizing a double-isotope technique, apoCII and apoCIII turnovers were found to be significantly increased in these two groups in vivo. Moreover, apoCII and apoCIII concentrations were increased in association with reduced $\text{apoCIII}\text{apoCII}$ ratios in both E and E+P groups. These results contrast to increased ratios reported in human subjects with associated hypertriglyceridemia. We conclude that administration of E alone or combined with P increases the synthesis and serum levels of several apoproteins, including apoC. These perturbations may be responsible for the inhibitory effects of serum from these animals on adipose tissue LPL. These events may modulate TG breakdown in peripheral tissues independent of direct effects of sex steroids on tissue LPL in these rats.     

Phosphotyrosine and phosphoprotein phosphatase activity of alkaline phosphatase in mineralizing cartilage

We used embryonic skeletal cartilage known to have high levels of alkaline phosphatase activity to determine whether growing cartilage has phosphotyrosine phosphatase activity and phosphotyrosinyl histone phosphatase activity at physiologic pH. Embryonic chick pelvic cartilage and fetal pig scapular growth-plate cartilage were assayed using phosphotyrosine as substrate at pH 7.5 and the amount of tyrosine generated measured. Both cartilage models had Km for phosphotyrosine between 6 to 24 mus mol/L. Phosphotyrosine phosphatase activity correlated with alkaline phosphatase activity as assessed by (1) distribution of histologic staining for alkaline phosphatase within the cartilages, (2) hormonal stimulation of cartilage alkaline phosphatase activity in vitro, (3) comparison of alkaline phosphatase and phosphotyrosine phosphatase activities in the presence of known inhibitors (vanadate, levamisole, homoarginine, and zinc), and (4) assaying chick epiphyseal cartilage alkaline phosphatase purified to homogeneity for phosphotyrosine phosphatase activity. Areas of cartilage with elevated alkaline phosphatase activity also had raised phosphotyrosine phosphatase activity. Triiodothyronine, a known stimulator of cartilage alkaline phosphatase, increased chick cartilage alkaline phosphatase activity 88% and phosphotyrosine phosphatase activity 106%, and stimulated porcine growth-plate cartilage alkaline phosphatase activity 91% and phosphotyrosine phosphatase activity 145% after 3 days of in vitro incubation. Each of the inhibitors block alkaline phosphatase and phosphotyrosine phosphatase activities. The purified alkaline phosphatase had a Km for phosphotyrosine of 18 mus mol/L and Vmax of 5700 nmol tyrosine/mg protein/h, which is well over 1000-fold higher than the phosphotyrosine phosphatase activity found in the above preparations of pelvic and scapular cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serologic studies in a family with heterozygous C2 deficiency

Twelve family members of a patient with systemic lupus erythematosus (SLE) and heterozygous deficiency of the second component of complement (C2) were studied. Histocompatibility (HLA) typing was determined for A, B, and DR and MB antigens. Serum samples were tested for a variety of antinuclear antibodies (ANA), lymphocytotoxic antibodies and rheumatoid factors, and C2 levels were determined by hemolytic titration. Inheritance of C2D, the gene coding for C2, was limited to the haplotype HLA-A25, B18, DR2. Low but significant titers of ANA, rheumatoid arthritis nuclear antigen (RANA) and/or rheumatoid factors were found in eight of the nine adult family members without association with HLA haplotype. The sister of the proband had persistently strongly positive LE cell preparations for more than a decade and had joint pains while taking sulfa drugs. The son of the proband had leukemia. All other family members were healthy. We conclude that the increased incidence of rheumatic disease in persons with C2D deficiency is multifactorial and requires environmental factors or other hereditary factors unrelated to the HLA-A25, B18, DR2 haplotype. The C2D gene is clearly not associated with positive ANA tests or immunoprecipitins to RANA.     

Riboflavin nutritional status and flavoprotein enzymes in normal and genetically diabetic KK mice

Riboflavin nutritional status in normal control Swiss albino (SA) and genetically diabetic (KK) mice aged 8–9 mo was assessed by determining the glutathione reductase activity in erythrocyte hemolysates, with and without addition of flavin adenine dinucleotide (FAD); the ratio (activity with added FAD)/(activity without FAD) was expressed as the activity coefficient (AC). AC values from 0.9 to 1.3 were considered normal and those greater than 1.3 were regarded as evidence of riboflavin deficiency. Among SA mice, 35% were found to be riboflavin deficient. Among KK mice, 83% were riboflavin deficient. The difference in prevalance was significant (p < 0.01). Supplementation of riboflavin to deficient KK mice returned their AC values to normal. Based upon AC values, both SA and KK mice were classified into normal (nondeficient) and riboflavin-deficient groups. Glutathione reductase (GR) activity in erythrocyte hemolysates and liver supernatants was significantly lower in both deficient SA and KK than in normal SA and KK mice. Treatment of deficient KK with riboflavin restored the enzyme activity in both preparations to normal. In contrast to the finding in erythrocytes, the hepatic GR activity was not increased by FAD in vitro either in normal or deficient mice. Hepatic mitochondrial succinate dehydrogenase (SDH) activity was significantly decreased in riboflavin-deficient KK mice. The enzyme activity was increased several-fold above normal in deficient KK mice supplemented with riboflavin. In conclusion, the data suggest that genetic diabetes increases the prevalence of riboflavin deficiency, which in turn causes a decrease in the erythrocyte and hepatic GR and hepatic SDH activities. This deficiency can be corrected by riboflavin supplementation, with subsequent augmentation of GR and SDH activities, indicating that these enzymes are dependent on the riboflavin nutritional status of the animal.     

The reflex sympathetic dystrophy syndrome (RSDS). III. Scintigraphic studies, further evidence for the therapeutic efficacy of systemic corticosteroids, and proposed diagnostic criteria

Sixty-four patients were evaluated prospectively for a reflex sympathetic dystrophy syndrome (RSDS), using quantitative clinical measurements, high-resolution roentgenography and scintigraphy. Five separate groups were identified by their clinical features, allowing us to distinguish patients with definite or incomplete forms of the RSDS as well as 16 patients with other disorders. Scintigraphy was found to be a useful diagnostic study that may also provide a method of predicting therapeutic response. Systemic corticosteroid therapy proved to be a highly effective mode of treatment for up to 90 percent of the patients with the RSDS.     

Na+ pump activity and nuclear T3 receptors in tissues of genetically obese (ob/ob) mice.

A dramatic reduction in ouabain-sensitive tissue respiration of obese mouse muscle and liver was observed, suggesting that Na+-transport-dependent calorigenesis is impaired in these animals. Additionally, a significantly depressed nuclear triiodothyronine binding capacity in liver and lung tissue was exhibited by obese mice. These data support the suggestion that the hypometabolism and hypothermia of the genetically obese mouse is a result of reduced Na+-pump-related thermogenesis; and further, provides evidence that this may be the consequence of reduced nuclear binding of triiodothyronine.     

Primary culture of adipoblasts from obese and lean Zucker rat adipose tissue

Adipocyte precursors derived from the epididymal fat pads of young adult lean (FaFa) and obese (fafa) Zucker rats were established in primary culture. The two types of culture were used to assess intrinsic cellular differences in proliferative capacity, lipoprotein lipase (LPL) activity and triglyceride (TG) accumulation related to genotype. Proliferative capacity was similar over seven days in vitro in lean- and obese-derived cultures. Heparin-releasable LPL activity was significantly greater in lean- than in obese-derived cultures grown in media supplemented with penicillin and streptomycin (pen-strep). However, when grown in media supplemented with cephalothin, heparin-releasable and total LPL activity increased significantly in obese-derived cultures and equalled LPL activity in lean-derived cultures. Substantial LPL activity was measurable in both types of culture at confluence, before exposure to media that promoted lipid-filling. TG accumulation was significantly greater in lean-than in obese-derived cultures in the presence of pen-strep but was similar in both culture types grown in cephalothin. These data support our hypothesis that the fa gene may affect mechanisms of protein turnover regulation, since pen-strep, but not cephalothin, has inhibitory effects on mammalian protein synthesis and degradation. The substantial LPL activity present in confluent, but unconverted cultures, suggests that some percentage of cells in the confluent monolayers are adipoblasts.