Biochemical and clinical effects of selenium on dimethylhydrazine-induced colon cancer in rats.

The biochemical and clinical effects of selenium (Na2SeO3) on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in male Sprague-Dawley rats are presented. A 4-ppm selenium supplement to the drinking water was provided before, during, and after 20 weekly injections of 20 mg DMH per kg body weight. Immediately after the 20th DMH injection, part of the rats were sacrificed. The incidences of colon tumors in groups provided selenium before DMH, before and during DMH, and only during DMH treatment were reduced to 39, 43, and 36%, respectively. The incidence in the DMH only control was 63%. Other rats in all treated and control groups were maintained up to 5 months post-DMH treatment. At 10-week intervals throughout the study, selected blood and tissue components were analyzed. The following hematological changes correlated with DMH treatment. (a) Serum glutamic oxalacetic transaminase increased 2-fold (normal, 66 +/- 14 g/dl). (b) Serum alkaline phosphatase increased 24% (normal, 166 +/- 56 units/liter). (c) Serum protein decreased 14% (normal, 6.77 +/- 0.48 g/dl). (d) White blood count increased 2- to 3-fold (normal, 7.7 +/- 2.7 X 10(3)/cu mm). And (e) hemoglobin decreased 67% (normal, 18.1 +/- 1.3 g/dl). The magnitude of these changes varies with each selenium treatment group and with each 10-week analysis period. Provision of 4 ppm selenium doubled both liver and blood selenium levels compared to unsupplemented controls. The effects of selenium and DMH treatments on glutathione peroxidase and beta-glucuronidase activities and on sialic acid are presented. Possible mechanisms by which selenium protects against DMH-induced neoplasia are discussed.

Effects of aging and estradiol supplementation on GH axis dynamics in women.

GH and IGF-I secretion decrease with age. The decline in serum GH with age appears to be associated with menopause. Prior studies of GH release before and after oral and transdermal hormonal replacement in the postmenopausal patient have shown no change or an increase in GH secretion. To distinguish the somatotropic axis effects of aging from those of estrogen deficiency, we compared eight prematurely menopausal women, aged 25-40 yr, with eight postmenopausal women, aged 51-70 yr, both before and after estradiol replacement. All women had a body mass index below 28 kg/m2. All were evaluated twice with frequent blood sampling every 10 min for 24 h. Studies were performed in the absence of exogenous hormones and 6-8 wk after transdermal estradiol replacement, targeted to achieve a serum estradiol level of 367 pmol/liter. GH pulsatility was analyzed. Variables tested included mean GH levels, interpulse baseline mean, pulse frequency per 24 h, and pulse amplitude. Transdermal estrogen replacement had a significant effect on mean GH levels and mean basal GH levels in both the premature ovarian failure and the age-appropriate postmenopausal group. No differences were noted in GH pulse frequency, GH pulse amplitude, IGF-I, IGF-binding protein-1, and IGF-binding protein-3 before and after treatment. A pronounced age effect was noted between the two groups. The premature ovarian failure women secreted significantly greater mean GH than the age-appropriate postmenopausal group regardless of treatment, with a significance level of P = 0.026. Interpulse baseline GH means were greater in the premature ovarian failure women than in the age-appropriate postmenopausal group, but the significance of this relationship was obliterated after adjustment for body mass index. Pulse amplitude was significantly increased in the premature ovarian failure women compared with age-appropriate postmenopausal women (P = 0.006). No significant changes were detected in the GH pulse frequency between the premature ovarian failure and postmenopausal groups. We conclude that moderate doses of transdermal estradiol supplementation do not exert a great effect on the somatotropic axis in women. Age and body composition appear to be the predominant influences on GH activity in women.

Luteal progesterone relates to histological endometrial maturation in fertile women.

To examine the relationship between endometrial histological maturation and reproductive hormones, we studied 11 fertile women, aged 18-37 yr. All participants had had at least 1 previous pregnancy and cycled regularly, every 25-35 days. Women collected daily, first morning voided urine for measurement of estradiol and progesterone metabolite excretion, estrone conjugates (E1c), and pregnanediol glucuronide (Pdg), respectively, throughout the cycle of study. Hormones were normalized for creatinine. Between 7-9 days after home detection of a LH surge (Sure Step), participants underwent an endometrial biopsy using a small bore (Pipelle) catheter. Tissue was prepared for histological and biochemical analyses. The histological analysis is reported herein. Endometrium was dated by 3 authors (N.S., D.H., and S.P.), all of whom were blinded to the participant's identity or timing of biopsy within her cycle. Final dating was agreed upon based upon the method of Noyes et al. E1c and Pdg were integrated throughout the cycle using the trapezoidal rule, and correlations were sought between deviation from expected histology (based upon urinary hormones and LH surge) and integrated hormone values. E1c varied over a 2-fold range in these normal women, from 1196-2040 ng/cycle. Pdg excretion was much more variable, ranging from 22-119 microg/cycle. No relationship could be found between histological lagging of endometrial maturation and lower excretion of E1c. A moderate correlation was observed (Spearman's r = 0.6; P < 0.05) between degree of histological maturation and integrated Pdg. Of two women with evidence of a disparity between gland and stromal development (glands lagging behind stroma by >2 days), one excreted 24 microg Pdg/cycle, the next to lowest value. We conclude that normal fertile women experience a wide range of hormone concentrations in the face of normal endometrial maturation. Progesterone appears to exert a dose-related effect on endometrial maturation, and the techniques we used, although relatively crude clinical measures, appeared to be sufficient to detect this relationship.

Evolution of metabolisms: a new method for the comparison of metabolic pathways using genomics information.

The abundance of information provided by completely sequenced genomes defines a starting point for new insights in the multilevel organization of organisms and their evolution. At the lowest level enzymes and other protein complexes are formed by aggregating multiple polypeptides. At a higher level enzymes group conceptually into metabolic pathways as part of a dynamic information-processing system, and substrates are processed by enzymes yielding other substrates. A method based on a combination of sequence information with graph topology of the underlying pathway is presented. With this approach pathways of different organisms are related to each other by phylogenetic analysis, extending conventional phylogenetic analysis of individual enzymes. The new method is applied to pathways related to electron transfer and to the Krebs citric acid cycle. In addition to providing a more comprehensive understanding of similarities and differences between organisms, this method indicates different evolutionary rates between substrates and enzymes.

The effect of the route of nutrient delivery on gut structure and diamine oxidase levels.

Diamine oxidase (DAO) is an intestinal mucosal enzyme which serves as a marker of cellular maturity and integrity in ontogeny and after mucosal injury in the gastrointestinal tract. Since total parenteral nutrition is known to result in intestinal hypoplasia, this study was done to determine the effect of enteral and parenteral delivery of nutrients on gut structure and DAO levels. Central venous catheters were placed in 27 Sprague-Dawley rats (180-260 g), which received nutrients for 12 days via parenteral nutrition (GpI n = 10), oral intake of the parenteral solution (GpII n = 8), or standard rat chow (GpIII n = 9). Gross and microscopic measurements were made at sacrifice. Mucosal DAO levels were determined by metabolism of [3H] putrescine. Group III animals had a greater caloric intake than groups I and II, and were the only group with a significant increase in body weight. Gut weight, mucosal weight, and villous height were significantly less in group I vs groups II and III; group II values were less than group III (p less than 0.05). Both DAO specific activity and total gut DAO were significantly less in group I and group II. Mucosal DAO content correlated with total gut and mucosal weight. DAO mucosal levels decrease with parenteral nutrition, reflecting the intestinal hypoplasia that occurs. Mucosal DAO content may be dependent on both caloric intake and diet composition. Since serum DAO levels are known to correlate with mucosal DAO content, DAO activity may prove useful as a circulating marker of the effect of nutritional therapy on the intestinal mucosa.

Sorption of selected polycyclic aromatic hydrocarbons on soils in oil-contaminated systems.

The adsorption and desorption behaviour of selected polycyclic aromatic hydrocarbons (PAHs) on different soils was investigated by static and dynamic methods. On the basis of a system including the four phases of soil, water, oil adsorbed and oil in emulsion, a model for the description of the adsorption behaviour in the presence of oil was developed. In systems without oil a similar partitioning behaviour in the batch and column experiments was observed for all PAHs. Thus the distribution coefficients can be calculated from the octanol/water coefficient of the aromatic compounds and the organic carbon content of the soils. The presence of a lipophilic phase had a significant influence on the sorption of the PAHs, usually resulting in a drastic decrease of adsorption with increasing oil content in the system. For the oil-contaminated system the modelling of the adsorption behaviour enabled a more detailed interpretation of the experimental observations as well as the calculation of the sorption behaviour for the PAHs from characteristic parameters of the components involved.

The lived experience of premature ovarian failure.

OBJECTIVE: To describe the lived experience of women who have been diagnosed with idiopathic premature ovarian failure (POF). DESIGN: Phenomenology was used to achieve the purpose. Women were asked to share their experiences in living with premature ovarian failure during an approximately 1-hour interview. The interviews were tape-recorded, transcribed, and analyzed for emergent themes. SETTING: Interviews were conducted in the participants' homes and in a conference room in a hospital. PARTICIPANTS: The six participants were drawn from a multicultural sample of women with idiopathic POF. RESULTS: The women in this study expressed anger at their health care providers for their perceived lack of quality care they had experienced and at the insurance industry for its lack of reimbursement for fertility interventions; they expressed depression and sadness at the prospective outcome of the diagnosis, mixed emotions regarding their significant others, and sadness and resignation about their menopausal symptoms. CONCLUSIONS: Health care providers who create an environment in which women and their significant others will feel supported in asking questions, be assured that their concerns are taken seriously, and be provided with the physical and emotional resources they need can help these women to continue to build and live their lives.

Chaotic interactions of self-replicating RNA.

A general system of high-order differential equations describing complex dynamics of replicating biomolecules is given. Symmetry relations and coordinate transformations of general replication systems leading to topologically equivalent systems are derived. Three chaotic attractors observed in Lotka-Volterra equations of dimension n = 3 are shown to represent three cross-sections of one and the same chaotic regime. Also a fractal torus in a generalized three-dimensional Lotka-Volterra Model has been linked to one of the chaotic attractors. The strange attractors are studied in the equivalent four-dimensional catalytic replicator network. The fractal torus has been examined in adapted Lotka-Volterra equations. Analytic expressions are derived for the Lyapunov exponents of the flow in the replicator system. Lyapunov spectra for different pathways into chaos has been calculated. In the generalized Lotka-Volterra system a second inner rest point--coexisting with (quasi)-periodic orbits--can be observed; with an abundance of different bifurcations. Pathways from chaotic tori, via quasi-periodic tori, via limit cycles, via multi-periodic orbits--emerging out of periodic doubling bifurcations--to "simple" chaotic attractors can be found.

Molecular evolution of catalysis.

In this paper, we consider the evolutionary dynamics of catalytically active species with a distinct genotype-phenotype relationship. Folding landscapes of RNA molecules serve as a paradigm for this relationship with essential neutral properties. The landscape itself is partitioned by phenotypes (realized as RNA secondary structures). To each genotype (represented as a sequence) a structure is assigned in a unique way. The set of all sequences which map into a particular structure is modeled as a random graph in sequence space (the so-called neutral network). A catalytic network is realized as a random digraph with maximal out-degree two and secondary structures as vertex sets. A population of catalytic RNA molecules shows significantly different behavior compared to a deterministic description: hypercycles are able to co-exist and out-compete a parasite with superior catalytic support. A "switching" between different dynamic organizations of the network can be observed, dynamical stability of hypercyclic organizations against errors and the existence of an error-threshold of catalysis can be reported.

Toxicological effects of sodium selenite in Sprague-Dawley rats.

Acute and chronic effects of Se as sodium selenite given as a supplement in the drinking water of Sprague-Dawley rats for 35 d, 1 yr, and 2 yr are compared. For the 35-d study the experimental groups were untreated controls and rats supplemented with 1, 4, 8, 16, and 64 ppm Se. Survival was 100% in the control and 1 and 4 ppm groups, decreased in the 8 and 16 ppm groups, and was zero in the 64 ppm group. Body weights increased and were equivalent in the control and 1 and 4 ppm groups and substantially decreased in the 16 and 64 ppm groups., Serum alkaline phosphatase and glutamic-oxaloacetic transaminase (SGOT) increased with 16 ppm Se and higher supplements. Se toxicity was apparent in microscopic pathology showing liver congestion, fatty degeneration of parenchymal cells, and necrosis. In the chronic studies untreated controls are compared with rate receiving 4 ppm Se in the drinking water. In general, the weight gains throughout were equivalent for both groups. The 1-yr survival in each was above 90% and the 2-yr survival above 50%. With increased age there was a slight reduction in hemoglobin and white blood cells. The latter effect was greater in Se-treated then in control rats. Several serum components were equivalent in both groups, including alkaline and acid phosphatase, SGOT, protein, glucose, and sialic acid. Liver glutathione peroxidase was half and Se levels in the Se-treated rats were twice those in the controls. Data are presented for male rats in the chronic study with occasional reference to data on females. The parameters measured in the chronic study are highly dependent on the age of the rat when Se-supplemented drinking water is initiated.

Toxicological effects of sodium selenite in Swiss mice.

Se as sodium selenite was administered by gavage (three consecutive times) and as drinking water supplements for 46 d to male and female Swiss mice. With respect to survival in 7-wk-old mice, Se was less toxic in males than in females when gavaged. Drinking water supplements of 1-64 ppm Se resulted in 1 male and 1 female death in mice first given Se at 7 wk of age. Se supplements to the drinking water of adult (18-wk-old) mice was less toxic in females. All young (7-wk-old) and adult (18-wk-old) mice provided 1-16 ppm Se in the drinking water survived the 46-d treatment, but in adult mice 64 ppm Se significantly reduced survival. Only 64 ppm Se supplements caused a sharp reduction in body weight in young and adult mice of both sexes. Supplements of 1-8 ppm Se in all mice elicited growth responses similar to those of untreated controls. Occasional liver and kidney congestion, liver necrosis, parenchymal cell degeneration, and bile duct proliferation were observed in control and treatment groups. Serum alkaline phosphatase and glutamic-oxaloacetic transaminase (SGOT) increased with 32 ppm Se and higher supplements. Survival, growth, serum enzymes, and pathology were normal in untreated controls and in mice of growth ages and sexes give 1, 4, and 8 ppm Se supplements. A chronic toxicity study was conducted in female Swiss mice given 1, 4, and 8 ppm Se supplements for 50 wk. The survival of Se-treated groups was more than 90% and that of controls was only 72% after 50 wk. All mice gained weight, but the group treated with 8 ppm Se gained half as much as other groups. Both liver Se and glutathione peroxidase activity increased in Se-treated mice compared to controls at 25 and 50 wk. A reduced white blood cell count and increased alkaline phosphatase and SGOT suggested a mild toxic effect of the 8 ppm Se supplement in the chronic study.

N-Methylation and N,N-dimethylation of amino acids. An artifact production in the analysis of organic acids using diazomethane as derivatizing agent.

In the fractions of the methyl esters of urinary organic acids seventeen N-methylated or N,N-dimethylated amino acid methyl esters are identified by gas chromatography-mass spectrometry. It is shown for twelve amino acids that their amino group reacts with diazomethane to form these derivatives. Using deuterated reagents, in particular deuterated diazomethane, in the sample preparation procedure during the organic acid analysis, it is shown that the N-methylated and N,N-dimethylated amino acids are artifacts from diazomethane and are not biochemical N-methylation products.

Basic profiles of organic acids in urine.

Altogether 143 of the organic acids regularly occurring in urine of healthy individuals are identified as methyl esters by gas chromatography-mass spectrometry with respect to their complete chemical structures. They are classified as dicarboxylic acids, oxocarboxylic acids, hydroxycarboxylic acids, aromatic acids, furancarboxylic acids, nitrogen-containing acids and acid conjugates. By pre-fractionating the complex mixture of the total organic acids, peak overlap is minimized, and substances in low concentrations can also be detected and identified. The qualitative patterns of the urinary organic acids in the fractions are constant and reproducible, and in many cases a reliable identification of organic acids is possible by gas chromatography alone, using methylene units and separation on OV-1701 capillary columns.

Phylogenetic analysis of metabolic pathways.

The information provided by completely sequenced genomes can yield insights into the multi-level organization of organisms and their evolution. At the lowest level of molecular organization individual enzymes are formed, often through assembly of multiple polypeptides. At a higher level, sets of enzymes group into metabolic networks. Much has been learned about the relationship of species from phylogenetic trees comparing individual enzymes. In this article we extend conventional phylogenetic analysis of individual enzymes in different organisms to the organisms' metabolic networks. For this purpose we suggest a method that combines sequence information with information about the underlying reaction networks. A distance between pathways is defined as incorporating distances between substrates and distances between corresponding enzymes. The new analysis is applied to electron-transfer and amino acid biosynthesis networks yielding a more comprehensive understanding of similarities and differences between organisms.

Hydroxycarboxylic and oxocarboxylic acids in urine: products from branched-chain amino acid degradation and from ketogenesis.

Hydroxy- and oxomonocarboxylic acids in urine of healthy individuals and of patients with diabetic ketoacidosis are analysed as methyl esters and methyl esters/O-methyloximes, respectively, by gas chromatography and gas chromatography-mass spectrometry. The derivatives are pre-fractionated by thin-layer chromatography. The acids originate mainly from ketogenesis and from the metabolism of valine, leucine and isoleucine. The amino acid metabolites fall into three groups: the 2-oxocarboxylic acids (2-oxoisovaleric acid, 2-oxoisocaproic acid and 2-oxo-3-methylvaleric acid); the 2-hydroxycarboxylic acids (2-hydroxyisovaleric acid, 2-hydroxyisocaproic acid and 2-hydroxy-3-methylvaleric acid); and the 3-hydroxycarboxylic acids (3-hydroxyisobutyric acid, 3-hydroxyisovaleric acid, 3-hydroxy-2-ethylpropionic acid, threo-3-hydroxy-2-methylbutyric acid and erythro-3-hydroxy-2-methylbutyric acid). The threo form of 3-hydroxy-2-methylbutyric acid is the major constituent within the diastereomeric pair. Of the three groups of amino acid metabolites, the 3-hydroxycarboxylic acids in particular are elevated during ketoacidosis. The characteristic general features of the mass spectrometric fragmentation of the derivatives of the identified components are systematically described. The discussion of the fragmentation includes constituents of low concentrations, such as 3-oxocaproic acid, 4-oxobutyric acid and 5-oxocaproic acid, which can be detected only when the pre-fractionation technique is applied.

Replication and mutation on neutral networks.

Folding of RNA sequences into secondary structures is viewed as a map that assigns a uniquely defined base pairing pattern to every sequence. The mapping is non-invertible since many sequences fold into the same minimum free energy (secondary) structure or shape. The pre-images of this map, called neutral networks, are uniquely associated with the shapes and vice versa. Random graph theory is used to construct networks in sequence space which are suitable models for neutral networks. The theory of molecular quasispecies has been applied to replication and mutation on single-peak fitness landscapes. This concept is extended by considering evolution on degenerate multi-peak landscapes which originate from neutral networks by assuming that one particular shape is fitter than all the others. On such a single-shape landscape the superior fitness value is assigned to all sequences belonging to the master shape. All other shapes are lumped together and their fitness values are averaged in a way that is reminiscent of mean field theory. Replication and mutation on neutral networks are modeled by phenomenological rate equations as well as by a stochastic birth-and-death model. In analogy to the error threshold in sequence space the phenotypic error threshold separates two scenarios: (i) a stationary (fittest) master shape surrounded by closely related shapes and (ii) populations drifting through shape space by a diffusion-like process. The error classes of the quasispecies model are replaced by distance classes between the master shape and the other structures. Analytical results are derived for single-shape landscapes, in particular, simple expressions are obtained for the mean fraction of master shapes in a population and for phenotypic error thresholds. The analytical results are complemented by data obtained from computer simulation of the underlying stochastic processes. The predictions of the phenomenological approach on the single-shape landscape are very well reproduced by replication and mutation kinetics of tRNA(phe). Simulation of the stochastic process at a resolution of individual distance classes yields data which are in excellent agreement with the results derived from the birth-and-death model.

Pathogenetic relevance of the pregnancy hormone relaxin to inborn hip instability.

The etiology of inborn hip dysplasia is unknown. In general, a multifactorial genesis is assumed. The influence of hormones on the development of the fetal hip joint and its stability is discussed as well as mechanical influences. This study was carried out with the intention to examine the correlation between the concentration of the pregnancy hormone relaxin and the stability of the hip joint in newborns. Both hips of 90 newborn children were examined clinically and sonographically. In 25 hips (13.9%), pathological sonograms according to the classification of Graf were found. The relaxin concentration was measured in cord blood using a heterologous radioimmunoassay. Statistical evaluation revealed an insignificant decrease of relaxin concentration with increasing sonographic hip instability. The results indicate that hip instability frequently occurs with decreasing relaxin concentration. These facts contradict the earlier assumption that hip instability coincides with increased relaxin concentrations in newborns. We assume that there is a worse preparation of the pelvis and the birth canal during pregnancy due to the lower relaxin concentration and thus that there could be a higher pressure on the fetus in the perinatal phase. A decreased relaxin concentration seems to have no direct effect on the hip joint tissue, but indirectly there is consequent rigidity of the tissue in mother and child, which can further promote the development of hip instability.

Gastric emptying of liquids and solids in the portal hypertensive rat.

The effects of portal hypertension on gastric motor function were investigated using the rat staged portal vein ligation model. Gastric emptying of liquids and solids was studied separately following meals labeled with 51Cr or 99Tc by whole stomach scintillation counting. Portal hypertension was consistently established in experimental rats (splenic pulp pressure: mean +/- SEM, portal hypertension versus control, 16.8 +/- 0.7 vs 11.8 +/- 0.7 mm Hg, P less than 0.0001). Although liquids were emptied in an exponential manner and solids in a linear fashion, gastric emptying of both meals was more rapid in the experimental rats. Ten minutes after the liquid meal, more than 50% of the meal had emptied from the stomachs of portal hypertensive rats while only one third of the meal had cleared in the control group (P less than 0.02). Gastric emptying of the solid meal was significantly accelerated in experimental rats at 60 and 120 min (percent meal remaining: portal hypertension versus control, 41.9 +/- 4.0 vs 55.4 +/- 3.5 and 21.5 +/- 4.9 vs 32.6 +/- 4.3, P less than 0.05). Stomachs of portal hypertensive animals were heavier (P less than 0.009) and histologic examination revealed submucosal edema. Thus, a possible mechanism of the disrupted gastric motor function in portal hypertension is decreased gastric wall compliance secondary to edema.

Small intestinal transit in the portal hypertensive rat.

The purpose of this study was to determine the effects of portal hypertension on gastrointestinal transit. Portal hypertension was induced in a group of 15 rats by the staged portal vein ligation technique. A control group of 15 rats underwent a sham operation. Ten days later, a 51Cr-labeled Krebs' buffer solution was instilled into the duodenum and the distribution or radioactivity along the length of the small intestine was determined after 15, 30, and 60 minutes. Portal hypertension was consistently established in the study group; splenic pulp pressure (mm Hg, mean +/- SD, portal hypertensive vs. control) was 20.0 +/- 3.9 vs. 12.7 +/- 3.9, P less than 0.002. Various measures of intestinal transit revealed delayed transit in the portal hypertensive group. Retention of radioactivity in the most proximal quartile of the intestine was greater [percentage retained (portal hypertensive vs. control) was 57.9 +/- 17.3 vs. 31.2 +/- 15.3, P less than 0.02, 49.1 +/- 15.5 vs. 28.3 +/- 4.8, P = 0.03, and 42.4 +/- 17.6 vs. 29.0 +/- 8.8, P = 0.08, at 15, 30, and 60 minutes, respectively] and the geometric mean of transit was located more proximally (P less than 0.02) at each study interval in the portal hypertension group. It was concluded that portal hypertension is associated with delayed intestinal transit. This abnormality could predispose to bacterial overgrowth and contribute to altered digestion and absorption.