Influence of fat level and type of carbohydrate on the capacity of pectin in lowering serum and liver lipids of young rats

The effect of pectin on lowering cholesterol and fat concentration in tissues of the rat was investigated in relation to the level of fat and the type of carbohydrate. Groups of rats were fed nutritionally complete diets containing equal protein: energy, varied with 5% (low-fat, 2% corn oil plus 3% beff tallow) or 20% (high-fat, 2% corn oil plus 18% beef tallow) fat and cornstarch or sucrose as carbohydrate for 2 weeks. Although there were no interactions, the feeding of pectin reduced the cholesterol level in liver and serum from dietary cholesterol to a greater degree in rats fed the low-fat than in those fed the high-fat diet. This effectiveness also varied with type of carbohydrate. In the low-fat diet, this effectiveness was higher with sucrose than with cornstarch, but in the high-fat diet, it was reversed. The size of perirenal fat pads and the concentrations of total liver lipid and cholesterol were less in rats fed the high-fat pectin diet than in those fed the high-fat diet without pectin, indicating that pectin also had an ability to lower fat absorption. When the level of serum alkaline phosphatase was lowered, pectin was more effective in lowering cholesterol level. This phenomenon, however, seemed due to the type of carbohydrate and fat rather than the cholesterol in the diet. Dietary cholesterol had no effect on the size of perirenal fat pads, but increased liver lipid content greatly in rats fed the high-fat diet. Dietary pectin increased the rate of removal of serum cholesterol, and a similar trend was shown in liver cholesterol which had accumulated from the pre-fed hyper-cholesterol diet.

Emetine myopathy in the rat

1 (-)Emetine (0.25-2.0 mg/kg i.p.) was administered to rats for up to 220 days. 2 At doses of 1.0 mg/kg or less, the animals continued to gain weight but more slowly than the untreated control animals. The physiological changes in the muscles from these animals were minimal; there was a small reduction in both the resting membrane potential and in the maximum rate of rise of the action potential. There was no atrophy or loss of muscle fibres although in the occasional muscle, hyaline fibres, necrotic fibres and split fibres were observed. There was a focal loss of myofibrillar adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) in Type II and Type III fibres, but no such loss in Type I fibres. 3 The animals receiving 2.0 mg/kg of (-)emetine gained weight slowly for up to 20 days but then rapidly lost weight and by 30 days they were weak and emaciated. The muscles from these animals were severly atrophied and the total muscle wet weight was reduced by almost 20%. 4 The strength of the muscles from these animals was measured in vitro using direct stimulation. They were weaker than normal both in absolute terms and when expressed in terms of tension developed/unit wet weight. 5 There was no evidence of either functional or structural denervation but surgically denervated muscles from animals in this group were indistinguishable from denervated muscles from normal rats. 6 Severe structural damage was obvious in the fibres of both extensor digitorum longus and soleus. Necrotic, hyaline and splitting fibres were common and the focal loss of myofibrillar ATPase and NADH-TR activity was extensive and occurred in Type I fibres as well as in Type II and Type II fibres. 7 It is concluded that the muscular weakness induced by (-)-emetine is due to a direct effect on the muscle fibres and that this occurs at a subcellular level. There is no evidence that functional or structural denervation plays any role in the aetiology of emetine myopathy in the rat.

Parabiotic reinnervation in normal and myopathic (BIO 14.6) hamsters

Parabiotic reinnervation is a technique whereby the muscles of one animal can be reinnervated by peripheral nerves of another animal. This technique has been used to test the hypothesis that the myopathy in the BIO 14.6 strain of hamster may result from a derangement of the trophic function that a nerve exerts upon the muscle which it innervates. The percentage of internal nuclei in muscle fibres has been used as a criterion to define the myopathic state. The percentage of internal nuclei was high in myopathic hamster muscles but very low in normal or "self-reinnervated" normal muscles. There was no indication that the percentage of internal nuclei in myopathic muscles fell after parabiotic reinnervation with normal nerves. Similarly, there was no evidence that the percentage increased in normal muscles that had been parabiotically reinnervated with dystrophic nerves. On the basis of these results, it was concluded that there was no positive evidence in favour of a neural aetiology for the myopathy in the BIO 14.6 strain of hamsters.

Stoppage of glycogenesis and "over-shoot" of induction of lipogenesis and its related enzyme activities in the liver of fasted-refed rats

To elucidate the causes of changes of carbohydrate metabolic pathways, the time course of utilization of dietary [U-14C]sucrose and induction of enzyme activities in the livers of rats were investigated. Adult male rats of BHE strain were refed after a fast of 2 days. The nutritionally complete refeeding diet contained 60% sucrose as the only source of carbohydrate. [U-14C]Sucrose was included in the diet on either day 1 or day 2, or both of refeeding. During the first day of refeeding, the radioactivity was incorporated mainly into liver glycogen which rose to over 100 mg/g. During the second day, little 14C appeared in the liver glycogen, which decreased sharply while glucose-6-phosphatase activity increased. The glycogenic pathway thus appeared to be blocked. On the other hand, 14C incorporation in the liver fat was minimal during the first day, but was quite extensive during the second day of refeeding. The enhanced lipogenesis was accompanied by large increases of activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP-malic dehydrogenase. Results clearly indicate that the carbohydrate load in the liver of intact animals was initially metabolized by the glycogenic pathway. When glycogenesis stopped, carbohydrate was metabolized differently. The enhanced incorporation of [U-14C]sucrose into liver lipids indicates an increased formation of acetyl CoA and an accelerated formation and use of NADPH, probably from increasing dehydrogenase activities. Our data suggest that the blockage of synthesis of glycogen with the continuation of carbohydrate load was a primary cause in over-shooting induction of hepatic dehydrogenase activities and lipogenesis.

Parabiotic reinnervation in normal and dystrophic mice. Part 2. Morphological studies

The technique of parabiotic reinnervation has been used to test directly the neurogenic theory of the aetiology of muscular dystrophy in mice. Dystrophic muscles contain significantly fewer muscle fibres than their normal controls; they also have a much broader spectrum of fibre size because of a much higher proportion of very small fibres and are poorly differentiated into histochemical fibre types. These criteria were used to assess whether there was any amelioration of the dystrophic process in response to the introduction of a normal nerve supply, or whether dystrophic changes were induced in normal muscle reinnervated with a dystrophic nerve. Self-reinnervated normal and dystrophic TA and EDL muscles contained the same numbers of fibres as unoperated controls. The process of parabiosis alone resulted in no changes in normal or dystrophic muscles. In the process of parabiotic reinnervation, the efficiency of the reinnervation process was not affected by the parabiotic state. The parabiotic reinnervation of dystrophic muscle by normal nerve resulted in no significant increase in fibre numbers and the spectrum of fibre sizes was essentially the same as in unoperated dystrophic muscle. The parabiotic reinnervation of normal muscle by dystrophic nerve resulted in a reduction of fibre numbers in only some of the muscles examined. However, the spectrum of fibre diameters remained essentially normal, and the differentiation of the fibres into histochemical fibre types was characteristic of reinnervated normal muscle. There was a marked absence of necrosis or of other histological signs of dystrophy in these muscles. Since there was no positive evidence to show that conversion of normal to dystrophic, or dystrophic to normal muscle occurred under the influence of parabiotic nerve transposition, two alternative conclusions were admissible. Firstly, the influence of dystrophic nerve upon muscle may be operative in fetal or neonatal life and may be irreversible by means of the subsequent introduction of a normal nerve supply. Secondly, the dystrophic state in muscle may be determined by genetic factors independent of nerve supply.

Effect of varying perfusion pressures on the output of sodium and renin and the vascular resistance in kidneys of rats with "post-salt" hypertension and Kyoto spontaneous hypertension

Isolated kidneys from both "post-salt" normotensive and hypertensive rats were perfused with blood from donor rats at varying pressures. At 130 mm Hg inflow pressure 15 "post-salt normotensive" kidneys put out 0.75 muEq Na/min/g kidney while 14 "post-salt hypertensive" kidneys put out 0.28 mu-Eq Na/min/g (P less than 0.001), a 63% reduction. They also put out 55% less water (P less than 0.002). Thus, if "hypertensive" kidneys are perfused at normal pressures, they put out subnormal amounts of Na and H-2-O. Such Na and H-2-O retention maintains the hypertensive state. Normal Na output in these kidneys was only reached at hypertensive (160) inflow pressures. This shift in the "pressure natriuresis" curve explains in part how some "hypertensive" kidneys maintain hypertension. These "hypertensive" kidneys have grossly abnormal autoregulation curves, each increment of pressure actually producing progressively greater increments of blood flow. Isolated kidneys from Kyoto hypertensive and normotensive rats showed no difference in Na and H-2-O excretion at 130 mm Hg inflow pressure. Thus, a tendency to Na retention demonstrable in the isolated kidney is apparently not supporting Kyoto hypertension. Moreover, isolated kidneys form Kyoto hypertensive rats released significantly lower amounts of renin at all levels of inflow pressure, averaging a 70% lower rate than Kyoto normotensive kidneys (P less than 0.01). Hence, Kyoto hypertension is not supported by a supernormal renin release inherent in the kidney. One can speculate that Kyoto hypertensive rats normally have an elevated sympathetic tone which stimulates release of renin. The denervation which occurs in isolating kidneys might therefore produce a proportionally greater percentage loss of sympathetic influence in these kidneys, which could possibly account for some of their reduced renin release. These Kyoto hypertensive kidneys are apparently not "reset" to maintain hypertension with either Na or renin.

ara-Cytidine acylates. Use of drug design predictors in structure-activity relationship correlation

This manuscript if one of a series of investigations into modifying the pharmacologic properties of the antitumor, antiviral, and immunosuppressive nucleoside ara-cytidine (cytarabine, Cytosar). The present paper summarizes our studies on depot ester derivatives of the nucleoside. We are able to predict with reasonable accuracy the biological activity as measured by increased life span in the L1210 leukemic mouse from a combination of two predictor variables: (1) the solubility of the ester in water and (2) its rate of hydrolysis by the mixed esterase system of animal plasma. We have tried unsuccessfully to correlate enzymatic hydrolysis rates with an alkaline hydrolysis model. Calculated Hansch partition (p) values had a correlation of r equal to 0.86 with water solubility. These p values had no additional predictive value. Based on our results, two esters were selected for clinical trial in cancer and rheumatoid arthritis.