Carbohydrate Starvation Research Articles

Hepatic messenger ribonucleic acid activity profile of rats subjected to alterations in thyroidal and adrenocortical states: evidence for significant interaction.

We have previously established the value of 2-dimensional electrophoretic mRNA activity profiles for investigating the hepatic genomic response to several metabolic perturbations, such as thyroid hormone or GH treatment, diabetes, high carbohydrate diet, starvation, and uremia. We now report the effects of adrenalectomy and dexamethasone treatment, and compare these with alterations due to thyroidectomy and T3 treatment. Total rat hepatic RNA was isolated and translated in a reticulocyte lysate system. The [35S]methionine-labeled translated products were separated by 2-dimensional gel electrophoresis and quantified with computerized videodensitometry. Of 200 consistently quantifiable products, 14 (7%) were altered by adrenalectomy and dexamethasone, including 4 products (46, 47, 56, and 57) which have not been observed to change in previous studies from this laboratory. Adrenalectomy increased 5 and decreased 2 products, whereas dexamethasone increased 1 and decreased 8 products. Two products maintained the same directional shift in the transitions form adrenalectomy to control and from control to the dexamethasone-treated state. Thyroidectomy and T3 altered 13 products. Thyroidectomy increased 2 and decreased 7 products, whereas T3 treatment increased 6 and decreased 3 products. Four products maintained the same directional shift in the transitions from thyroidectomy to control and from control to the T3-treated state. In all of the manipulations performed (adrenalectomy, thyroidectomy, dexamethasone treatment, and T3 treatment), a total of 20 separate products changed. One third were affected by alterations of both the steroidal and thyroidal states. However, when adrenalectomy and thyroidectomy were compared, only 7% of the shifts were concordant, whereas 30% of the shifts were concordant when treatment with dexamethasone and T3 were compared. These results demonstrate that the mRNA activity response is highly specific for each hormonal manipulation. In addition, unanticipated interrelationships between steroidal and thyroidal states were observed. In some, the presence of T3 appears necessary for the suppressive effect of dexamethasone. Others show that T3 appears to inhibit a stimulatory effect of dexamethasone. Specificity of response to dexamethasone is emphasized by the lack of response to vitamin D, deoxycorticosterone, and dihydrotestosterone and by a different response to estradiol from dexamethasone.

Effects of nutrition and ontogeny on liver cytosolic and mitochondrial phosphoenolpyruvate carboxykinase activity of the rat, hamster, guinea-pig, pig, kid, calf and chick

1. 1. In rat, hamster, guinea-pig, pig, kid, and calf liver, starvation or carbohydrate starvation increased cytosolic phosphoenolpyruvate carboxykinase activity without changing the mitochondrial activity whereas in chick liver, starvation did not alter the activity in both fractions. 2. 2. Liver glycogen content changed in a reciprocal way to the cytosolic phosphoenolpyruvate carboxykinase activity. 3. 3. In prenatal kid and chick liver, phosphoenolpyruvate carboxykinase activity appeared in both cytosolic and mitochondrial fractions, and in chick liver, considerable increase of the cytosolic activity was observed from a few days before hatching to 4 days after hatching.

Lateral Root Anlage Development in Excised Roots of Vicia faba L., Pisum sativum L., Zea mays L. and Phaseolus vulgaris L.

The development of lateral root primordia has been investigated in excised roots of Vicia faba, Pisum sativum, Zea mays and Phaseolus vulgaris cultured in White's medium supplemented with 2 per cent sucrose and compared with previously published data on such development in primaries of the corresponding intact plants (control roots). Primordia were produced in each batch of excised roots over the 6 day culture period but at a lower rate (number day−1) than in the controls. Such primordia in cultured roots of Zea and Phaseolus completed their development and grew out as lateral roots over a period similar in length to that found in the controls, but with a cell number of only about 33 per cent of that attained at the time of secondary emergence in the primaries of the latter roots. These lower cell numbers were at least partly a reflection of increases in mean cell doubling time over the period of anlage development investigated in the excised roots relative to the corresponding values found in the controls. Primordia initiated in excised roots of Pisum and Vicia did not complete their development in culture, i.e. no lateral roots emerged and arrest took place with cell numbers of only 37 (Pisum) and 17 (Vicia) per cent of the numbers determined at the time of secondary root emergence in the controls. Such arrested primordia had few nuclei in S and none in mitosis. Moreover, at least in Pisum, the frequency distribution of the relative DNA content of the nuclei in the latter primordia approximated that found in the apical meristem of primary roots following the establishment of the stationary phase under conditions of carbohydrate starvation. It has also been demonstrated in the course of these investigations that lateral root primordium development in all four species is at least biphasic and possibly triphasic.

Pea ( Pisum sativum) cells arrested in G2 have nascent DNA with breaks between replicons and replication clusters

DNA fiber autoradiography and alkaline sucrose sedimentation of DNA of cultured pea-root cells ( Pisum sativum) arrested in G2 by carbohydrate starvation demonstrated that nascent DNA molecules of replicon (16–27 × 10 6 D) and apparent cluster (~330 × 10 6 D) size were not joined. That the arrested cells were in G2 was confirmed by single-cell autoradiography and cytophotometry. In pea there are about 18 replicons per average cluster, 4.2 × 10 3 clusters, and 7.7 × 10 4 replicons per genome.

Preferential resynthesis of muscle glycogen in fasting rats after exhausting exercise.

Despite carbohydrate starvation (fasting or fat feeding) considerable glycogen accumulation, ranging from 20 to 30 mumol glucose/g, occurred in hindlimb muscles of rats following exhausting exercise that caused severe muscle and liver glycogen depletion and hypoglycemia. The largest increase in muscle glycogen occurred during the first 3 h after exercise when plasma levels of glucagon and epinephrine were very high and insulin concentration was low. The concentrations of glycogen attained in different hindlimb muscles in the fasting and fat-fed animals were between 50 and 100% of the values found in rats fed carbohydrate after the exhausting exercise. In rats fed carbohydrate following exercise, liver glycogen accumulation greatly exceeds muscle glycogen accumulation. A remarkable difference in the response of liver glycogen was seen in the carbohydrate starved rats. In contrast to the rapid increase in muscle glycogen, liver glycogen was still essentially completely depleted in the fasting and fat-fed rats 24 h after exercise. This indicates that the glucose made available via gluconeogenesis was preferentialy channeled away from liver glycogen synthesis into muscle glycogen.

Sugar and Amino Acid Content of Poa pratensis Infected with Ustilago striiformis and Urocystis agropyri

AbstractLeaf and root tissues of Poa pratensis L. showing distinct morphological changes associated with infection by Ustilago striiformis (West.) Niessl var. poae (stripe smut) or Urocystis agropyri (Pruess) Schroet. (flag smut) were analyzed for total soluble sugars and free amino acids. Decreases in the quantity of soluble sugars in stripe‐smutted plants were not significant, indicating that the presence of U. striiformis sori in leaf tissue does not interfere with photosynthesis of the host. Severe decreases in the quantity of soluble sugars in flag‐smutted plants suggest that U. agropyri either directly impairs photosynthesis or effectively metabolizes the photosynthate. Both pathogens caused significant decreases in total free amino acids in leaf and root tissues. The negligible decrease in soluble sugars in stripe‐smutted plants was associated with a disproportionate decrease in free amino acids, suggesting that the pathogen either metabolizes amino acids or inhibits their synthesis. The severe decrease in amino acids in leaves and roots of U. agropyri‐infected plants is believed due to carbohydrate starvation. It is probable that morphological changes in U. agropyri‐infected plants, including reduced branching, dwarfed leaves and root systems, and the inability to produce inflorescences, are probably the direct result of severely reduced levels of sugars and amino acids. The reduced branching, somewhat smaller root systems, and inhibition of inflorescence production on plants infected by U. striiformis probably are associated to some extent with decreases in amino acids. The upright elongated leaves of U. striiformis‐infected plants, however, cannot be attributed to the decrease in amino acid content and are suggestive of hyperauxiny.

Effect of carbohydrate restriction and high carbohydrate diets on men with chemical diabetes

The influence of low carbohydrate (CHO) diets, starvation, and high CHO diets on glucose tolerance tests (GTT) and plasma insulin response of men with chemical diabetes was studied. The GTT and insulin responses of these seven lean diabetic men were unchanged when the carbohydrate content of the diet was reduced from 44 to 20% of calories. After a 48-hr fast a significant deterioration of the GTT was observed in these diabetic men but the percentage change was identical to that reported previously for normal men. Thus these studies indicate that changes in glucose mtes are quite similar to those reported previously for normal men. The fasting plasma glucose values of seven lean and four obese men with chemical diabetes were significantly lower after one week on a 75% CHO diet than values on a 44% CHO diet. The 75% CHO diet also was accompanied by slight improvements in the oral and intravenous GTT and by slightly lower plasma insulin responses. The improvement in glucose metabolism on high CHO diets appears to results from increased insulin sensitivity. Serum triglyceride values were approximately 55% higher on the 75% CHO diet than values on the 44% CHO diet for the 11 men but these differences were not statistically significant. These studies support previous observations and suggest that high CHO diets may be beneficial in the management of certain diabetic patients. However, further studies are required to determine the long-term effects of high CHO diets containing natural foods on the glucose and lipid metabolism of diabetic patients.

The Position and Characteristics of ‘Leaky’ Cells in Root Tip Meristems ofHelianthus annuus

Sunflower root meristems are composed of two populations of cells which respond differently to stress. One population becomes arrested in Gi and G2, while the second 'leaky' population (0-25-1-0 per cent) is able to pass through S even during carbohydrate starvation. Leaky cells enter S at a rate of 0-06 per cent cells h-1 after 48 h of starvation. The character of leakiness is retained by roots starved for two successive 48 h starvation periods separated by an 8 h sucrose pulse. Single and double layer autoradiograph experiments demonstrated that leaky cell progeny maintain their leaky character through at least two cell generations. Leaky cells are located at random in the root cap, promeristem, ground meristem, protoderm, cortex, and pericycle. The presence of leaky cells may indicate a stress response mechanism to repopulate the root meristem.

DNA fiber replication of chromosomes of pea root cells terminating S

Autoradiographic analysis of chromosomal DNA fiber replication was used to measure the distance between initiation points of adjacent replicons and the rate of fiber growth during cessation of proliferation that results from carbohydrate starvation of pea root meristem cells. The rate of fiber growth at 23 °C decreased from 34 μm/h/fork at 3 h to less than 2 μm/h/fork at 24 h of starvation. The distance between initiation points, i.e., the average replicon size, was 36–38 μm in starved cells terminating S. Replenishment of carbohydrate was accompanied by an increase in the rate of fiber growth and larger replicons.

The quiescent centre in excised roots of Pisum sativum L.

Excised roots ofPisum sativum were cultured in White's medium supplemented with various concentrations of sucrose or IAA and exposed to3H-TdR for 24 hours, three days after excision. Varying the concentration of sucrose or IAA in the culture medium had no effect on the size of the quiescent centre in the apical meristem of these roots. It is concluded that the existence of a quiescent centre in angiosperm roots is not due to carbohydrate starvation or to the super-abundance, or lack of, IAA.

Development and control of intestinal and hepatic fructokinase.

Extract: The patterns of development of intestinal and hepatic fructokinase have been studied in the rat, in the rabbit, and in man, and information regarding the mechanism of control of this enzyme in mature organs has been obtained. Fructokinase activity was detectable 4 days before term in fetal rat jejunum (1.0 nmol/min/mg protein) and rose progressively to a plateau 20-fold greater by the 20th day of life (20 nmol/min/mg protein). The enzyme in rat ileum and liver and in rabbit liver behaved similarly (rising from 0.5 to 4.0 nmol/min/mg protein (ileum) and from 0.5 to 8.5 nmol/min/mg protein (liver)). In human fetal liver, there was a threefold rise in fructokinase activity from approximately the 10th to 24th week of gestation (increasing from 2.1 to 7.8 nmol/min/mg protein); jejunal activity rose slightly, but not significantly, during this period. As expected, feeding of mature rats with sucrose after prolonged carbohydrate starvation led to a twofold increase in jejunal (from 6.05 to 13.0 nmol/min/mg protein) and hepatic (from 14.1 to 24.2 nmol/min/mg protein) fructokinase activity. The administration of actinomycin before the introduction of sucrose inhibited the carbohydrate-stimulated rise in fructokinase activity in both organs. Similarly, injection of actinomycin during sucrose feeding produced a significant fall in enzyme activity which greatly exceeded that produced by fasting alone. The data suggest that the substrate-dependent activity of this enzyme may be regulated at the level of transcription. Speculation: These studies support the hypothesis that the genetic control of certain enzymes involved in carbohydrate metabolism can be influenced by exogenous factors, among them dietary carbohydrate.

CELL ARREST IN Gl AND G2 OF THE MITOTIC CYCLE OF VICIA FABA ROOT MERISTEMS

Experiments were performed with cultured excised primary root tips of Vicia faba ‘Longpod’ to determine: (1) the proportion of meristematic cells arrested in Gl and in G2 during carbohydrate starvation, and to determine if the proportion is fixed or can be varied experimentally; (2) the effect of increased starvation on the ability of arrested cells in Gl and G2 to initiate DNA synthesis and mitosis, respectively, when exogenous sucrose was supplied; and (3) whether puromycin, cycloheximide, or actinomycin D prevented the initiation of DNA synthesis and the onset of mitosis. Microspectrophotometry of nuclear DNA and autoradiographic measurements of incorporated 3H‐thymidine showed that 72 hr of starvation immediately after excision produced tissue with more than 70 % of the cells arrested in G2 and less than 30 % in Gl. If cultured for three days and then starved for 72 hr, the tissue had nearly equal numbers of cells arrested in Gl and G2. As the duration of starvation increased, the time required to initiate DNA synthesis and to divide when carbohydrate was replenished also increased. Inhibition of protein synthesis by puromycin and cycloheximide prevented the initiation of DNA synthesis and mitosis, but actinomycin D, an inhibitor of RNA synthesis, did not prevent division of cells from G2 nor DNA synthesis by cells from Gl. The experiments demonstrated that the mitotic cycle of Vicia has two major controls, one in Gl and another in G2, and that other factors determine how many cells are affected by either of these cycle controls.

Additional Studies on the Regulation of Carbohydrate-Dependent Enzymes in the Jejunum: Changes in Amino Acid Pools, Protein Synthesis, and the Effect of Actinomycin-D.

Adaptive changes in rat jejunal disaccharidase levels during carbohydrate starvation and carbohydrate feeding were studied in relation to protein synthesis, amino acid pools, and cell migration. When animals were fed a sucrose-rich, normal protein diet for 24 hr after being on a casein-rich, carbohydrate-free diet for 7 days, there was 50% reduction in the size of the total amino acid pool without a significant change in the proportions of individual amino acids in the pool. The specific radioactivity of the leucine pool increased whenever carbohydrate was added to the diet and protein intake reduced. The incorporation of radioactive precursors into homogenate and brush border proteins reflected the characteristics of the pools, and was thus higher during carbohydrate feeding when the pool size was smaller. The rate of cell migration was unaffected by diet. Disaccharidase activities fell during prolonged carbohydrate starvation. When animals were treated with actinomycin-D, ribonucleic acid synthesis measured 18 hr later was reduced 50%, and cell migration was arrested. The drug did not inhibit the sucrose-stimulated rise in homogenate sucrase activity, although it did abolish the expected increase in fructokinase activity. With actinomycin-D treatment, brush border sucrase activity did not parallel the increases seen in the homogenate, but rather fell markedly. The data demonstrate that dietary carbohydrate increases jejunal disaccharidase activity without elevations in the rate of protein synthesis and that the effect is also independent of ribonucleic acid synthesis and cell migration. By contrast, jejunal fructokinase activity is probably regulated at the level of transcription.

CELL PROLIFERATION IN COMPLEX TISSUES: THE CONTROL OF THE MITOTIC CYCLE OF CELL POPULATIONS IN THE CULTURED ROOT MERISTEM OF SUNFLOWER (HELIANTHUS)

Experiments were performed with cultured primary root tips of sunflower (Helianthus annuus var. Russian Mammoth) to determine: (1) if progression in the mitotic cycle of meristematic cells was nutritionally controllable by carbohydrate starvation and replenishment; (2) where in the mitotic cycle control was effected; and (3) whether nutritional deprivation could be used to detect phenotypically different subpopulations in a complex tissue. Meristematic cells were rendered stationary by carbohydrate starvation, as indicated by the absence of cell division; this condition was reversed by carbohydrate provision. After 72 or 96 hr of starvation most cells stopped in G1 (80–90%) and G2 (10–20%), and a very few (“leaky” cells) continued to enter S. “Leaky” cells represent a small population with an S period of approximately 4.1 hr that either lack a principal control point in G1 or have an unusual metabolism whereby the control point requirements are met and have a carbohydrate dependence for mitosis. Though phenotypically different, no specific functions can be attributed to “leaky” cells at this time.

Primary anorexia nervosa or weight phobia in the male: report on 13 cases.

The cases of 13 men with anorexia nervosa are reported. While the disorder as seen in the clinic is much less common in males than females this may not be a true reflection of the differential sex or overall prevalence rates. The disorder is found to have the same basic characteristics in the male as in the female: namely, a phobic avoidance of normal weight associated with elective carbohydrate starvation and emaciation. As in the female the mechanism appears to develop out of normal adolescent dieting behaviour and to arise as a means of avoiding overwhelming psychosocial maturational demands of adolescence. Premorbid and family features include a state of overnutrition and a high degree of family psychopathology reflected in high rates of parental psychiatric morbidity and marital difficulty.

Intracellular processing of disaccharidases: The effect of actinomycin D

1. 1. The effects of actinomycin D on the specific activities and intracellular distribution of rat jejunal disaccharidases were studied in rats fed a standard lab chow diet and a carbohydrate-free diet. With the standard diwet, brush border sucrase and lactase activities decreased 50% within 18 h of actinomucin D injection (0.25 μg/g body wt.), and continued to fall with further drug treatment, Maltase activity in teh brush border remained at control levels for the first 23 h, but then declined progressively. By contrast, sucrase and lactase activities in both jejunal homogenates and microsomal fractions increased sifnificantly within 24 h of actinomycin D administration. However, with continued treatment sucrase activity in the homogenates fell rapridly while lactase and maltase activities declined more slowly. No significant change occurred in isolmaltase activity in either homogenates or brush borders. Actinomycin D cuased a 50% reduction in total jejunal RNA synthesis 18 h after injection. Incorporation of 14C-labelled amino acids into total jejunal and microsomal proteins was not affected, but the labelling of brush border proteins showed a profressive reductino during the first 24 h after injection of actinomycin D. In rats maintained on a carbohydrate-free diet, disaccharidase activities fell below the levels found in animals n the standard diet. Furthermore, actinomycin D did not cause the early rise in the specific activities of sucrase and lactase in jejunal homogenates seen with carbohydrate feeding. Actinomycin D added to homogenates and brush borders in vitro had no effect on enzyme activity. 2. 2. These results suggest that the mechanismsm controlling the intracellular levels of the individual disaccharidases function independently, and that in the presence of dietary carbohydrate actinomycin D effects a change in teh intracellular distribution of these enzymes which is abolished by carbohydrate starvation. The data also support hypothesis that an actinomycin D sensitive step is required for the transfer of disaccharides from sites of synthesis to the brush border.

Dependence on energy and aerobic metabolism of initiation of DNA synthesis and mitosis by G1 and G2 cells

Following establishment by carbohydrate starvation of a stationary phase in pea root tip meristems, the requirements for initiation of cell proliferation were investigated. Entry of G1 cells into S (DNA synthesis), G2 cells into M (mitosis) and progression of G1 cells through S and G2 into mitosis were prevented by carbohydrate starvation, anaerobiosis or treatment with 2,4-dinitrophenol. The data show that ( a) both DNA synthesis and mitosis require aerobic conditions and are energy-dependent and ( b) events prior to the initiation of these processes have relatively greater energy requirements than the rest of the mitotic cycle.

A controlled study of the EEG in anorexia nervosa.

The nutritional disturbance in anorexia nervosa almost invariably leads to striking physiological changes, which include amenorrhoea, bradycardia, hypotension and relative hypothermia with reversal of the usual diurnal temperature rhythm (Bliss and Branch, 1960; Mayer-Grosset al., 1960; Crisp and Roberts, 1962; Crisp, 1967a). Crisp (1965a, 1967a) has commented on the characteristic and excessive alertness, restlessness and insomnia displayed by anorexia nervosa patients, whom he regards as showing a specific type of malnutrition associated with carbohydrate starvation. Russell (1967) has also recently demonstrated that patients with this illness restrict especially their carbohydrate intake.

Note on study of the sporulation of fungi: endotrophic sporulation in the genus Penicillium.

Conidiophore formation and sporulation can be induced inPenicillium sp. strain P 17 by an environmental factor—carbohydrate (carbon) starvation. Both surface and submerged mycelium, when transferred from synthetic medium to glucose-free salt solution, form conidiophores and sporulate, while in the control cultures on complete medium, vegetative growth continues. The time required for the formation of conidiophores, i.e. the induction interval, is 7–14 h and its length increases with the age of both surface and submerged mycelia. During the induction phase the mycelium undergoes autolysis, associated with degradation of energy motabolism involving the comsumption of reserve substances, a rapid drop in endogenous respiration and the endogenous reducing activity of the mycelium, a decrease in the labile phosphate concentration, proteolysis, an increase in the ammonia and orthopsphate concentration and exhaustion of readily oxidized amino acids from the pool. A transient increase in respiration occurs before differentiation of the conidiophores starts. During the second half of the induction phase, polyphenol substances and polyphenol oxidase appear in the mycelium.The enzyme is not induced by exogenous phenols. Its possible role in the sporulation of fungi is considered.

Serum cholesterol levels in anorexia nervosa.

IN CONTRAST to earlier investigators (Pardee, 1941; Stephens, 1941; Emmanuel, 1956) more recent workers (Crisp, 1965a, 1967; Oberdisse, Solbach & Zimmerman, 1965; Klinefelter, 1965; Crisp & Stonehill, 1967) have reported that some of their patients with anorexia nervosa have high serum cholesterol levels. Crisp (1965a, b, 1967) in a study of eighty patients (Nos. 1-80) has also emphasized that anorexia nervosa is predominantly a state of severe chronic carbohydrate starvation having its origins in the patient's phobia of and consequent need to avoid normal adolescent weight. Such patients who will have initially turned to eating supposedly 'non-fattening' foods such as as cheese, fruit, meat and salad, may later surrender to their increasing impulse to eat carbohydrate by having binges. They may start to vomit in relation to their binges and conceal and deny one or both these aspects. Usually such binges also alternate with phases when the patient stops eating altogether. Such cycles may recur every 24 hr or may span several weeks. These complex and often interrelating patterns of feeding make it more than usually difficult to assess the past dietary intake. Meanwhile, a further study by Crisp et al. (1967) has confirmed that thirty-seven female patients aged 14-33 with anorexia nervosa had significantly higher serum cholesterol levels (P<0 0002) than thirty-seven normal women with whom they were matched individually for age (Fig. 1). The serum cholesterol levels in the control group are the mean of two results from the two halves of the menstrual cycle. However, there was a wide variation of serum cholesterol levels amongst the anorexia nervosa group. It was confirmed that such levels bore no relationship to thyroid function or reduced plasma volume and were unlikely to be due to diminished oestrogen activity, a universal characteristic in