Showing papers on "B vitamins published in 1992"

The 65-kDa subunit of human NF-kappa B functions as a potent transcriptional activator and a target for v-Rel-mediated repression.

Abstract: Molecular cloning of the polypeptide component of the Rel-related human p75 nucleoprotein complex has revealed its identity with the 65-kDa (p65) subunit of NF-kappa B. Functional analyses of chimeric proteins composed of NF-kappa B p65 C-terminal sequences linked to the DNA-binding domain of the yeast GAL4 polypeptide have indicated that the final 101 amino acids of NF-kappa B p65 comprise a potent transcriptional activation domain. Transient transfection of human T cells with an expression vector encoding NF-kappa B p65, but not NF-kappa B p50, produced marked transcriptional activation of a basal promoter containing duplicated kappa B enhancer motifs from the long terminal repeat of type 1 human immunodeficiency virus. These stimulatory effects of NF-kappa B p65 were synergistically enhanced by coexpression of NF-kappa B p50 but were completely inhibited by coexpression of the v-rel oncogene product. Together, these functional studies demonstrate that NF-kappa B p65 is a transactivating subunit of the heterodimeric NF-kappa B complex and serves as one cellular target for v-Rel-mediated transcriptional repression.

Relocation and distinct subcellular localization of p34cdc2-cyclin B complex at meiosis reinitiation in starfish oocytes.

Abstract: M phase promoting factor (MPF) is a major element controlling entry into the M phase of the eukaryotic cell cycle. MPF is composed of two subunits, p34cdc2 and cyclin B. Using indirect immunofluorescence staining with specific antibody against starfish cyclin B, we monitored the dynamics of the subcellular distribution of MPF during meiosis reinitiation in starfish oocytes. We found that all of the cyclin B is already associated with p34cdc2 in immature oocytes arrested at the G2/M border and that this inactive complex is present exclusively in the cytoplasm. After its activation, part of the p34cdc2-cyclin B complex moves into the germinal vesicle before nuclear envelope breakdown, independently of either microtubules or actin filaments. Thereafter, some part of the complex accumulates in the nucleolus and condensed chromosomes. Another portion of the complex accumulates on meiotic asters and spindles, while the rest is still present throughout the cytoplasm. As these patterns of localization are detected in the detergent-extracted oocytes, we propose at least four distinct subcellular states of the p34cdc2-cyclin B complex: freely soluble, microtubule-associated, detergent-resistant cytoskeleton-associated and chromosome-associated. Thus, in addition to the intramolecular modification of p34cdc2-cyclin B complex, its intracellular relocation plays a key role in promoting the M phase.

The c-rel protooncogene product c-Rel but not NF-kappa B binds to the intronic region of the human interferon-gamma gene at a site related to an interferon-stimulable response element.

Abstract: Interferon-gamma (IFN-gamma) is an important immunoregulatory protein that is expressed usually only in large granular lymphocytes and T cells. The gene encoding IFN-gamma was previously found to contain an intronic enhancer element that was not tissue-specific in its activity, despite the restricted expression of the intact IFN-gamma-encoding gene. Using nuclear extracts from the human T-cell line Jurkat, we have now identified two protein-binding regions in this intronic enhancer element. One of the protected regions has strong partial identify to the NF-kappa B site present in the promoter region of the human interleukin 2-encoding gene. Based on this observation and recent reports of the interaction of the c-rel protooncogene product (c-Rel) with NF-kappa B sites, we determined whether c-Rel could interact with the intronic enhancer element in the human IFN-gamma genomic DNA. Most surprisingly, gel-shift analysis, using c-Rel expressed in Escherichia coli established that c-Rel binds specifically to the IFN-gamma intronic DNA but not to the interleukin 2-like NF-kappa B site. Additional studies with antibodies prepared against c-Rel peptides verified specificity of the interaction of c-Rel with this binding site. In addition, using an affinity-purified p50 subunit of the NF-kappa B complex, we observed that the p50 protein did not bind to this additional c-Rel-binding site. Furthermore, nucleotide sequence analysis of this DNA region revealed a strong similarity of the additional c-Rel-binding site to a previously identified IFN-stimulable response element. These data show that c-Rel can interact with DNA regions distinct from that recognized by NF-kappa B and may, in fact, be involved in transcriptional regulation of the IFN-stimulable genes via the IFN-stimulable response element.

Biology of the chicken MHC (B complex).

Abstract: The major histocompatibility complex (MHC) of chicken is the B complex, originally described as a blood group system. Its three classes of cell membrane antigens have been clearly defined by serological, histogenetic, biochemical, and molecular biological methods. Two of these classes are homologous to classes I and II of mammals (B-F and B-L respectively), while the third--B-G antigen--has not so far been detected in mammals. The possible role of this antigen is discussed. The genes of the MHC play important roles in the regulation of immune response, disease resistance, and regression of Rous sarcomas.

Vitamin content of camel milk.

Abstract: The content of vitamin C, vitamin B2 and fat-soluble vitamins E and A in camel milk was studied. The milk samples were collected from 20 individual camels (Camelus dromedarius) in two different occasions. The study showed that camel milk contains considerably less vitamin A and B2 than cow milk while the content of vitamin E was about the same level. The level of vitamin C was in average three times higher than that of cow milk.

Kappa B site-dependent activation of the interleukin-2 receptor alpha-chain gene promoter by human c-Rel.

Abstract: The cis-acting control elements of the interleukin-2 receptor alpha-chain (IL-2R alpha) gene contain a potent kappa B-like enhancer whose activity can be induced by various mitogenic stimuli. Recent cloning of the p50 and p65 subunits of the kappa B-binding protein NF-kappa B complex revealed a striking sequence homology of these proteins with the c-rel proto-oncogene product (c-Rel). On the basis of this homology, we examined the potential role of c-Rel in controlling IL-2R alpha transcription. We now demonstrate that the recombinant human c-Rel protein binds to the kappa B element in the IL-2R alpha promoter and results in alteration of the DNA structure in the adjacent downstream regulatory elements containing the CArG box and the GC box. We found that human c-Rel can activate transcription from the IL-2R alpha promoter, but not the kappa B-containing human immunodeficiency virus type 1 promoter, upon cotransfection into Jurkat T cells. Furthermore, truncation of the carboxyl terminus of c-Rel results in a c-Rel mutant (RelNA) that (i) localizes exclusively in the nucleus and (ii) acts in synergy with wild-type c-Rel in activating transcription from the kappa B site of the IL-2R alpha promoter. Finally, induction of surface IL-2R alpha expression coincides with the induced levels of endogenous c-Rel and induced c-Rel binding to the IL-2R alpha kappa B site. Our study identified c-Rel as one component of the Rel/NF-kappa B-family proteins involved in the kappa B-dependent activation of IL-2R alpha gene expression. Furthermore, our results suggest that a Re1NA-like cellular factor (e.g., NF-kappa B p50 or p49 subunit) acts in synergy with c-Re1 during T-cell activation.

Evidence for diminished B12 absorption after gastric bypass: oral supplementation does not prevent low plasma B12 levels in bypass patients.

Abstract: Vitamin and mineral assays were performed on blood in 20 gastric bypass patients preoperatively and 6 and 12 months postoperatively. Values were compared with serial food records in nine patients. Postoperatively, all patients were prescribed a supplement containing the recommended dietary allowances (RDA) for vitamins and minerals. Weight, calorie and protein intake, and total serum protein decreased over the study interval (p less than 0.01). Dietary intakes of vitamins B1, B2, B6, folate, iron and zinc fell (p less than 0.01), but total intake (i.e., diet + supplement) did not decrease with the exception of iron. Blood indicators of these nutrients were normal preoperatively and did not decline. However, plasma vitamin B12 levels decreased from 385 pg/ml preoperatively to 234 pg/ml at 1 year (p = 0.0064), despite an increase in total vitamin B12 intake from 2.6 to 11.7 micrograms/day (p = 0.1173). Five patients (27.8%) had abnormally low plasma vitamin B12 levels at 1 year postoperatively; four were taking at least the RDA for vitamin B12 as supplements. Although oral supplementation containing the RDA for micronutrients can prevent abnormal blood indicators of most vitamins and minerals, it is insufficient to maintain normal plasma B12 levels in about 30% of gastric bypass patients.

Brief communication. Vitamin B1, B2, and B6 augmentation of tricyclic antidepressant treatment in geriatric depression with cognitive dysfunction.

Abstract: This was a 4-week randomized placebo-controlled double-blind study to assess augmentation of open tricyclic antidepressant treatment with 10 mg each of vitamins B1, B2, and B6 in 14 geriatric inpatients with depression. The active vitamin group demonstrated significantly better B2 and B6 status on enzyme activity coefficients and trends toward greater improvement in scores on ratings of depression and congnitive function, as well as in serum nortriptyline levels compared with placebo-treated subjects (Ss). Without specific supplementation, B12 levels increased in Ss receiving B1/B2/B6 and decreased in placebo Ss. These findings offer preliminary support for further investigation of B complex vitamin augmentation in the treatment of geriatric depression.

Effects of vitamin B12 on plasma melatonin rhythm in humans: increased light sensitivity phase-advances the circadian clock?

Abstract: Vitamin B12 (methylcobalamin) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatonin rhythm was significantly phase-advanced (1.1 h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 trial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.

Induction of monocytic differentiation and NF-kappa B-like activities by human immunodeficiency virus 1 infection of myelomonoblastic cells.

Abstract: The effects of human immunodeficiency virus 1 (HIV-1) infection on cellular differentiation and NF-kappa B DNA binding activity have been investigated in a new model of myeloid differentiation PLB-985 cells represent a bipotential myelomonoblastic cell population capable of either granulocytic or monocytic differentiation after induction with appropriate inducers By virtue of the presence of CD4 on the cell surface, PLB-985 cells were chronically infected with HIV-1 strain IIIB PLB-IIIB cells clearly possessed a more monocytic phenotype than the parental myeloblasts, as determined by differential staining, increased expression of the myeloid-specific surface markers, and transcription of the c-fms proto-oncogene NF-kappa B binding activity was inducible by tumor necrosis factor and phorbol myristate acetate in PLB-985 However, in PLB-IIIB cells, constitutive expression of a novel NF-kappa B complex was detected, composed of proteins ranging between 70 and 110 kD These proteins interacted specifically with the symmetric NF-kappa B site from the interferon beta (IFN-beta) promoter Mutations affecting the 5' guanine residues of the kappa B site were unable to compete for these NF-kappa B-related proteins Inducibility of endogenous IFN-beta and IFN-alpha RNA was also increased in PLB-IIIB cells These studies indicate that HIV-1 infection of myelomonoblastic cells may select for a more mature monocytic phenotype and that unique subunit associations of NF-kappa B DNA binding proteins may contribute to differential NF-kappa B-mediated gene expression

Cobalt-vitamin B-12 deficiency decreases methionine synthase activity and phospholipid methylation in sheep.

Abstract: Two groups of lambs were fed either a Co-deficient or a Co-sufficient whole barley-based diet for 28 wk to induce a severe Co-vitamin B-12 deficiency. Holo and apo methionine synthase activities were significantly lower in the liver, kidney and spinal cord of Co-deficient animals compared with controls. Neither form of this enzyme in the brain was affected by Co deficiency. The ratio of the tissue concentrations of S-adenosyl methionine to S-adenosyl homocysteine was significantly lower only in the liver of Co-deficient animals, suggesting that the activity of hepatic SAM-dependent methyltransferase enzymes would be impaired. Measurements of tissue concentrations of phosphatidyl choline and phosphatidyl ethanolamine revealed lower concentrations of phosphatidyl choline and a lower phosphatidyl choline:phosphatidyl ethanolamine ratio in both liver and brain of the Co-deficient animals. The latter finding occurred in the absence of changes in either methionine synthase activity or the methylation ratio and may result from impaired availability of hepatic phosphatidyl choline for transport into the brain.

The transport of thiamine, riboflavin and pyridoxal 5'-phosphate by human placenta.

Abstract: In the present examination the concentrations of thiamine, riboflavin and pyridoxal 5'-phosphate in blood plasma of pregnant women and venous and arterial cord plasma were determined. In maternal plasma the concentration was 4.5 nmol/l (thiamine), 22.2 nmol/l (PLP), 8.7 nmol/l (free riboflavin) and 84.5 nmol/l (FAD + FMN). In venous cord plasma the concentration was 45.9 nmol/l (thiamine), 112.1 nmol/l (PLP), 40.6 nmol/l (free riboflavin) and 49.1 nmol/l (FAD + FMN). Therefore the gradients of concentration between maternal plasma and venous cord plasma were 1:10 for thiamine, 1:4.7 for free riboflavin and 1:5 for PLP. For the coenzyme forms of vitamin B2 the maternal circulation showed the higher concentration (1.7:1). Therefore an active transplacentar transport mechanism was assumed. The vitamin concentrations in cord arteria were significantly lower than that in cord vene, indicating a massive retention by the fetus.

Vitamin-humic-algal root biostimulant increases yield of green bean

Abstract: Over the past decade there has been a not-able increase of research on the use of nat-urally derived or organic materials inagriculture (Poincelot, 1986; Russo and Ber-lyn, 1990). Some of these are biostimulants,i.e., nonnutritional products that may reducefertilizer use and increase yield and resis-tance to water and temperature stresses.Among the materials that stimulate plantgrowth in relatively small amounts (Aitkenet al., 1964; Berlyn and Russo, 1990; Kin-nersley et al., 1989; Senn, 1987; Senn andKingman, 1973) are humic acids, marine al-gae, polymers of lactic acid, B vitamins, andascorbic acid. Under certain conditions,biostimulants work well (Russo and Berlyn,1990) and suggest possible uses in horticul-ture.We tested “Roots” (Lisa Products Corp.,New Haven, Conn.), a proprietary mixtureof humic acids, marine algae extracts, thia-mine, and ascorbic acid. The objective ofthis study was to assess the effectiveness ofthis organic biostimulant (OB) on pod pro-duction of green beans (Phaseolus vulgarisL.).Seeds of beans cv. Bush Blue Lake 274(Agway Inc., Syracuse, N.Y.) were sownand germinated in trays filled with vermi-culite. In test A, the first set of 120 seedlingswas transplanted, one seedling per pot, to2.8-liter pots that contained a 1 potting soil(Agway) : 1 vermiculite (v/v) mix. The sta-tistical design was a completely randomizedfactorial (Statview II, Abacus Concepts,

Changes in carotenoids and fatty acids in photosystem II of Cudeficient pea plants

Abstract: Photosystem II (PSII) from Cu-deficient pea plants (Pisum sativum L., cv. Lincoln) has been investigated for electron transport activity, Cu content, and changes in some lipid components. Total fatty acid content was lower that in control plants, with an additional shift in the C18 fatty acid patterns. Less α-linolenic and more linoleic and oleic acids were found. PSII preparations from Cu-depleted plants showed a decreased carotenoid content in light harvesting chlorophyll a/b complex of photosystem II (LHCII) and additional variations in pigment composition of pigment-protein complexes. In the green alga Dunaliella the effect of Cu deficiency on fatty acid composition was similar to that in pea plants, but the influence on the carotenoid pattern was much less pronounced.

Crystal Structure of Papain-Succinyl-Gln-Val-Val-Ala-Ala-p-Nitroanilide Complex at 1.7-A Resolution: Noncovalent Binding Mode of a Common Sequence of Endogenous Thiol Protease Inhibitors?

Abstract: Succinyl-Gln-Val-Val-Ala-Ala-p-nitroanilide corresponding to a common sequence of endogenous thiol protease inhibitors is a noncompetitive reversible inhibitor of papain. In order to elucidate the binding mode of the inhibitor at the atomic level, its complex with papain was crystallized at ca. pH 7.0 using the hanging drop method, and the crystal structure was analyzed at 1.7-A resolution. The crystal has space group P2(1)2(1)2(1), with a = 43.09, b = 102.32, c = 49.69 A, and Z = 4. A total of 47,215 observed reflections were collected on the imaging plates using the same single crystal, and 19,833 unique reflections with Fo > sigma (Fo) were used for structure determination and refinement. The papain structure was determined by use of the atomic coordinates of papain previously reported, and then refined by the X-PLOR program. The inhibitor molecule was located on a difference Fourier map and fitted into the electron density with the aid of computer graphics. The complex structure was finally refined to R = 19.6% including 118 solvent molecules. The X-ray analysis of the complex crystal shows that the inhibitor is located at the R-domain side, not in the center of the binding site created by the R- and L-domains of papain. Such a binding mode of the inhibitor explains well the biological behavior that the inhibitor exhibits against papain. Comparison with the structure of papain-stefin B complex indicates that the structure of the Gln-Val-Val-Ala-Gly sequence itself is not necessarily the essential requisite for inhibitory activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary arginine influences Rous sarcoma growth in a major histocompatibility B complex progressor genotype.

Abstract: L-Arginine (L-Arg) can serve as a substrate for the production of reactive nitrogen intermediates. One of these metabolites, nitric oxide, has been shown to possess significant antitumor properties in vitro. To investigate the importance of this system in vivo, we have examined the dietary L-Arg host tumor interaction in the chicken. Since chickens are incapable of de novo L-Arg synthesis, concentration of this amino acid is readily controlled by diet. Line UNH 105 New Hampshire chickens having the major histocompatibility complex genotype, B24/B24, were used to study in vivo effects of dietary L-Arg on Rous sarcoma growth. After 5 weeks on a standard diet, 119 chicks were fed either a basal (0.92% L-Arg) diet or a high arginine (2.40% L-Arg) diet. One week later, chicks were wing-web inoculated with subgroup A Rous sarcoma virus. Tumor growth was monitored weekly for 12 weeks after inoculation. Plasma L-Arg levels and body weights from birds on each dietary treatment were analyzed. Neither body weight gains nor latent period for tumor development was affected by diet. However, plasma L-Arg levels were significantly different between dietary treatments (basal, 0.245 +/- 0.01 mumol/ml; high, 0.738 +/- 0.03 mumol/ml). In addition, mean tumor size scores were significantly (P less than 0.05) lower over time in chickens fed the high L-Arg diet. The results suggest that dietary L-Arg in excess of the amount required for growth reduces tumor load.

Korsakoff minus Wernicke syndrome.

Abstract: It is commonly believed that Korsakoff's amnesic state in alcoholics is characteristically the sequel to Wernicke's disease. However, in a study of 44 Korsakoff patients it was found that 33 had developed serious memory impairment without having had alarming neurological symptoms. This insidious nature of the onset of the disease indicates that all alcohol-dependent patients should be treated with vitamin B.

The kappa B enhancer motifs in human immunodeficiency virus type 1 and simian virus 40 recognize different binding activities in human Jurkat and H9 T cells: evidence for NF-kappa B-independent activation of the kappa B motif.

Abstract: The kappa B transcriptional enhancer motif, present in many viruses, is broadly active in many cell types. It is recognized by c-Rel/HIVEN86A in DNA affinity precipitation (DNAP) assays and by the Rel-related p50 and p65 subunits of the nuclear factor NF-kappa B in electrophoretic mobility shift assays (EMSA). We have analyzed activities that bind the human immunodeficiency virus type 1 and simian virus 40 kappa B motifs in two human leukemia cell lines, Jurkat and H9. In both DNAP and EMSA analyses of Jurkat cell extracts, we detected multiple kappa B motif-binding activities in addition to c-Rel/HIVEN86A and p50-p65 NF-kappa B. In Jurkat cell nuclear extracts, EMSA analysis revealed at least six specific DNA-protein complexes, of which one comigrated with the p50-p65 NF-kappa B complex. Formation of all six complexes was enhanced by stimulation of the cells with phorbol 12-myristate-13-acetate and phytohemagglutinin but was differentially affected by the salt concentration in the binding reaction and by the conditions of Jurkat cell growth. Nuclear extracts from both unstimulated and stimulated H9 cells revealed similar levels of five kappa B motif-specific complexes, all of which displayed mobilities distinct from those of the Jurkat cell complexes. Indeed, a complex corresponding to p50-p65 NF-kappa B was not detectable in nuclear extracts from unstimulated H9 cells although such a complex was apparent in nuclear extracts from stimulated H9 cells. In contrast to the inducibility of a p50-p65 NF-kappa B-like complex, transcriptional enhancers composed of multimerized kappa B motifs displayed similar high levels of activity in both the unstimulated and stimulated H9 cells. Thus, the activity of the kappa B motif in H9 cells corresponded to the abundance of the H9 cell-specific kappa B motif complexes and not to the levels of p50-p65 NF-kappa B complex. These results suggest that the broad activity of the kappa B enhancer element is not only due to the broadly distributed NF-kappa B activator but also to cell type-specific kappa B motif-binding activities.

Meat, poultry, and fish consumption and nutrient intake in the healthy elderly.

Abstract: Food selection of the healthy elderly may be influenced by life-styles, the food supply, and recommendations related to diet and disease. This study used food group analysis of 3-day diet records to examine red meat, poultry, and fish consumption by free-living, healthy elderly individuals. Dietary data were from 122 women and 97 men (median age = 75 years) who were participants in the New Mexico Aging Process Study in 1984. Mean dietary intake was 1,494 kcal/day for women and 2,079 kcal/day for men--82% and 94% of the Recommended Dietary Allowance (RDA), respectively. Protein, iron, and selected B vitamins were above 100% of the RDA. Women's mean daily intake of meat/poultry/fish was 87.7 g (52.1 g meat, 23.6 g poultry, 12.0 g fish); men's intake of meat/poultry/fish was 121.2 g (78.4 g meat, 21.2 g poultry, 21.6 g fish). Of the total red meat, more than 50% was beef, 20% was pork/ham, and more than 10% was processed meat. For women, meat/poultry/fish provided 14% of total dietary energy, 37% of protein, 13% to 32% of selected B vitamins and iron, 20% of fat, and 34% of cholesterol. Percentages were similar for men. There was no significant association between age and total dietary intake, but food group consumption had distinct associations with age for women and men. Our findings indicate that a moderate but not excessive intake of meat/poultry/fish made a substantial contribution to nutrient intake. The fat contribution of these food groups could be decreased by emphasizing lower-fat selections of meat, poultry, and fish.

Estimation of the dietary riboflavin required to maximize tissue riboflavin concentration in juvenile shrimp (Penaeus monodon).

Abstract: The riboflavin requirements of marine shrimp (Penaeus monodon) were evaluated in a 15-wk feeding trial. Juvenile shrimp (initial mean weight, 0.13 +/- 0.05 g) were fed purified diets containing seven levels (0, 8, 12, 16, 20, 40 and 80 mg/kg diet) of supplemental riboflavin. There were no significant differences in weight gains, feed efficiency ratios and survival of shrimp over the dietary riboflavin range. The riboflavin concentrations in shrimp bodies increased with the increasing vitamin supplementation. Hemolymph (blood) glutathione reductase activity coefficient was not a sensitive and specific indicator of riboflavin status of the shrimp. The dietary riboflavin level required for P. monodon was found to be 22.3 mg/kg diet, based on the broken-line model analysis of body riboflavin concentrations. Shrimp fed unsupplemented diet (riboflavin concentration of 0.48 mg/kg diet) for 15 wk showed signs of deficiency: light coloration, irritability, protuberant cuticle at intersomites and short-head dwarfism.

Association of cyclin-bound p34cdc2 with subcellular structures in xenopus eggs.

Abstract: Cell cycle progression is controlled by changes in kinase activity of homologs of the fission yeast protein p34cdc2. The p34cdc2 kinase is activated by its association with a cyclin subunit, followed by post-translational modifications. Here, we show that in Xenopus eggs stimulated to enter the early embryonic cell cycle by an electric shock, part of the p34cdc2 becomes associated with subcellular fractions as the eggs progress towards mitosis. This occurs as a result of cyclin accumulation because most of the B-type cyclins and some of the A-type cyclins are found in the particulate fraction. Moreover, as soon as cyclins are degraded, p34cdc2 is released in the soluble fraction. The p34cdc2-cyclin complex can be solubilised by 80 mM beta-glycerophosphate (in the standard MPF extraction buffer) or by high salt concentrations. The post-translational modifications leading to cdc2 kinase activation by cyclin occur in the insoluble form. Following fractionation of egg extracts by sucrose gradient centrifugation, the p34cdc2-cyclin B complex is found in several fractions, but especially in two discrete peaks. We present evidence that in the slow-sedimenting peak the p34cdc2-cyclin B complex is associated with the 60 S subunit of monoribosomes. It could be targeted in this fashion to substrates such as ribosomal proteins and maybe to cytoskeletal proteins, since ribosomes bind to microtubules and are present in the spindle. The p34cdc2-cyclin B complex is also found in a faster-migrating fraction containing various membranous structures, including Golgi stacks. Therefore, as observed by immunofluorescence in other systems, it seems that cyclin subunits target p34cdc2 to specific cellular sites and this is certainly important for its function. In addition, we present preliminary evidence suggesting that some component present in the ribosome-containing fraction is required for activation of the p34cdc2-cyclin B complex.

Micronutrient supplementation in children on continuous cycling peritoneal dialysis (CCPD).

Abstract: Data on the micronutrient (vitamin and trace mineral) requirements of children on chronic peritoneal dialysis is limited. Few preparations are of suitable content and palatability. In a prospective study we have assessed and compared the serum levels and dietary intakes of micronutrients (vitamins A, E, B12, folate and zinc, copper, iron) in 7 children on CCPD who were receiving either Ketovite tablets (vitamins C, E and B complex) and Cholecalciferol or a more comprehensive supplement, Paediatric Renal Seravit (vitamins A, E, D, C and B complex with trace minerals). All children received nutritional supplements orally or via a gastrostomy button. These supplements contributed significantly to their nutritional intakes. The mean dietary intakes of the studied micronutrients, with the exception of vitamins A, E, B12 and folate, were below RDA (USA) values. The Renal Seravit was tolerated by only 5 of the 7 patients. There was no significant difference in serum levels of the micronutrients while on the Paediatric Renal Seravit compared to Ketovite. Serum iron levels remained low on both supplements. A comprehensive micronutrient supplement may still be required in children on prolonged dialysis.