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Biomedical subjects

R B Rucker

Publications and source records attributed to R B Rucker.

At least 19 recordsLinked to original sources
PubMed1992

Enzymatic and nonenzymatic cross-linking of collagen and elastin.

Knowledge regarding the steps and mechanisms related to the intra- and interchain cross-linking of collagen and elastin has evolved steadily during the past 30 years. Recently, effort has been directed at identifying the location and types of cross-links that are found in collagen and elastin. There are two major groups of cross-links: those initiated by the enzyme lysyl oxidase and those derived from nonenzymatically glycated lysine and hydroxylysine residues. The formation of enzymatic cross-links depends on specific enzymes, amino acid sequences, and quaternary structural arrangements. The cross-links that are derived nonenzymatically occur more adventitiously and are important to pathobiological processes. Considerable progress has been made in elucidating the pathways of synthesis for several of the enzymatically mediated cross-links, as well as possible mechanisms regulating the specificity of cross-linking. Although less is known about the chemistry of cross-links arising from nonenzymatically glycated residues, recent progress has also been made in understanding possible biosynthetic pathways and control mechanisms. This review focuses on such progress and hopes to underscore the biological importance of collagen and elastin cross-linking.

Animals↗
PubMed1991

Physiologic importance of pyrroloquinoline quinone.

Pyrroloquinoline quinone (PQQ, methoxatin) is a dissociable cofactor for a number of bacterial dehydrogenases. The compound is unusual because of its ability to catalyze redox cycling reactions at a high rate of efficiency and it has the potential of catalyzing various carbonyl amine reactions as well. In methylotrophic bacteria, PQQ is derived from the condensation of L-tyrosine with L-glutamic acid. Whether or not PQQ serves as a cofactor in higher plants and animals remains controversial. Nevertheless, a strong case may be made that PQQ and related quinoids have nutritional and pharmacologic importance. In highly purified, chemically defined diets, PQQ stimulates animal growth. Furthermore, PQQ deprivation appears to impair connective tissue maturation, particularly when initiated in utero and throughout perinatal development.

Bacteria↗
PubMed1991

Intestinal absorption and tissue distribution of [14C]pyrroloquinoline quinone in mice.

Pyrroloquinoline quinone (PQQ) functions as a cofactor for prokaryotic oxidoreductases, such as methanol dehydrogenase and membrane-bound glucose dehydrogenase. In animals fed chemically defined diets, PQQ improves reproductive outcome and neonatal growth. Consequently, the present study was undertaken to determine the extent to which PQQ is absorbed by the intestine, its tissue distribution, and route of excretion. About 28 micrograms of PQQ (0.42 microCi/mumol), labeled with 14C derived from L-tyrosine, was administered orally to Swiss-Webster mice (18-20 g) to estimate absorption. PQQ was readily absorbed (62%, range 19-89%) in the lower intestine, and was excreted by the kidneys (81% of the absorbed dose) within 24 hr. The only tissues that retained significant amounts of [14C]PQQ at 24 hr were skin and kidney. For kidney, it was assumed that retention of [14C]PQQ represented primarily PQQ destined for excretion. For skin, the concentration of [14C]PQQ increased from 0.3% of the absorbed dose at 6 hr to 1.3% at 24 hr. Furthermore, most of the [14C]PQQ in blood (greater than 95%) was associated with the blood cell fraction, rather than plasma.

Administration, Oral↗
PubMed1991

Does the intestinal microflora synthesize pyrroloquinoline quinone?

Pyrroloquinoline quinone (PQQ) functions as a cofactor for prokaryotic oxidoreductases, such as methanol dehydrogenase and glucose dehydrogenase. When chemically-defined diets without PQQ are fed to animals, lathyritic changes are observed. In previous studies, it was assumed that PQQ was produced by the intestinal microflora; consequently, antibiotics were routinely added to diets. In the present study this assumption is tested further in mice by: (i) examining the effects of dietary antibiotics on fecal PQQ excretion, (ii) isolating the intestinal flora to identify bacteria known to synthesize PQQ and (iii) determining in vitro if the intestinal microflora synthesizes PQQ from radio-chemically labeled precursors. The results of these experiments indicate that little if any PQQ is synthesized by the intestinal microflora. Rather, when PQQ is present in the intestine, the diet is a more obvious source.

Animals↗
PubMed1990

Collagen, proteoglycan and hyaluronidase activity in cultures from normal and scoliotic chicken fibroblasts.

Connective tissue matrix components were investigated using skin fibroblasts from normal or inbred scoliotic lines of chickens. Specifically, the fibroblasts were obtained from either an isogenic line or a backcross, derived by crossing the isogenic line with a pure line of scoliotic birds. From the backcross, both affected (35-45%) and non-affected (55-65%) progeny were produced. The affected birds had spinal curves greater than 20 degrees. Several abnormalities of connective tissue were observed when cells from scoliotic chicks were grown in culture: increased collagen extractability, decreased aggregatability of proteoglycans under associative conditions and lower than normal levels of hyaluronic acid. There was also less collagen deposited in the cell layer with proportionately increased amounts of collagen secreted into the culture media by cells from scoliotic versus normal chick fibroblasts. Values for collagen matrix stability, as estimated by extractability and net deposition, were intermediate for cells from the backcrossed, but non-affected, birds. Moreover, hyaluronidase, an enzyme that degrades hyaluronic acid, was abnormally elevated in the fibroblast cultures from scoliotic chicks. It is proposed that the increase in hyaluronidase contributes to the abnormalities observed in extracellular matrix components and may be a factor in the expression of scoliosis in susceptible birds.

Animals↗
PubMed1989

Nutritional importance of pyrroloquinoline quinone.

Mice fed a chemically defined diet devoid of pyrroloquinoline quinone (PQQ) grew poorly, failed to reproduce, and became osteolathyritic. Moreover, severely affected mice had friable skin, skin collagen that was readily extractable into neutral salt solutions, and decreased lysyl oxidase. The identification of functional defects in connective tissue and the growth retardation associated with PQQ deprivation suggest that PQQ plays a fundamental role as a growth factor or vitamin.

Animals↗
PubMed1989

Ontogenic development of the elastic component of the aortic wall in spontaneously hypertensive rats.

In the neonatal stage of development in spontaneously hypertensive rats (SHR), previous studies have shown that arterial pressure is already significantly increased over that of normotensive WKY controls and that other hypertensive characteristics of the cardiovascular system are also in evidence. The present study describes early development of the elastic component of the aortic wall in fetal (days 17, 19, 21-22 of gestation) and neonatal (days 1, 7, 14, 21 of age) SHR and WKY, to determine whether the early pattern of elastin accumulation differs significantly in hypertensive and normotensive animals. The data indicate that in SHR there is a greater concentration of elastin in the aortic wall, a larger cross-sectional area and an increase in the number of lamellar units, both pre- and postnatally. We conclude that the differences in arterial wall structure which are associated with genetic hypertension are established early in development.

Animals↗
PubMed1989

Accumulation and regulation of elastin in the rat uterus.

The relative levels of elastin-specific mRNA were used as a measure of tropoelastin expression in uteri from pregnant Sprague-Dawley rats. The levels of elastin-specific mRNA were also correlated with values for net tropoelastin production and net deposition of mature, crosslinked elastin. The total content of uterine elastin increased throughout gestation, reaching maximal levels at Day 19 of gestation, which were three times those of nongravid tissue. Following involution, the elastin content decreased rapidly to near baseline values by 5 days postpartum. The content of soluble elastin, estimated using an enzyme-linked immunosorbent assay, paralleled in part the increase in elastin deposition and elastin mRNA levels. Uterine elastin metabolism appears to be unlike that in other elastic tissues, e.g., lung and large blood vessels. In most elastin containing tissues, the protein is synthesized during discrete developmental periods and is not readily degraded. However, uterine elastin is continuously expressed, and appears to be in a continual cycle of degradation and replacement.

Animals↗
PubMed1988

Superoxide dismutase activity in lung from copper- and manganese-deficient mice exposed to ozone.

Nutritional manganese (Mn) or copper (Cu) deficiency was investigated in Swiss-Webster mice exposed to ozone (O3). Mice rendered Mn-deficient were first reared from Mn-deficient dams and then fed a Mn-deficient (1 microgram/g) diet. Mice rendered Cu-deficient were fed a diet containing 0.2 microgram Cu/g diet. Control mice were fed a diet containing Mn at 45 micrograms/g and Cu at 8 micrograms/g. During the last week of the experiment (week 7, post-weanling), mice in each group were exposed continuously to 1.2 ppm O3 or filtered air for 7 days. Superoxide dismutase (SOD) activity in lung was then estimated. In mice breathing filtered air, neither lung Cu,Zn- nor Mn-SOD activity (U/g) was affected by diet. In O3-exposed mice, however, Mn-SOD activity was lower in the Mn-deficient group and Cu, Zn-SOD activity was lower in the Cu-deficient group. Moreover, total lung Cu,Zn-SOD activity was elevated in the Mn-deficient mice, whereas total Mn-SOD activity was elevated in the Cu-deficient mice in response to O3. These data indicate that under normal circumstances lung Cu,Zn-SOD and Mn-SOD are not affected by Cu or Mn deficiency. However, when an oxidant stress is superimposed on the Cu- or Mn-deficient condition, Cu,Zn- and Mn-SOD activities are impaired.

Animals↗
PubMed1988

Cofactors in and as posttranslational protein modifications.

A symposium at the FASEB meeting in Las Vegas in May 1988 will be devoted to the role of cofactors (vitamins, coenzymes, prosthetic groups) in and as posttranslational protein modifications; the symposium is part of a thematic focus on metabolic regulation. In planning the symposium, we decided to consider metabolic regulation in its broadest context, which should include both the short-term activity modulations in the life of contemporary organisms and the adaptations of special molecular strategies over evolutionary time. We further decided to focus the symposium context on the involvement of cofactors both as catalytic participants in and as substrates or end products of posttranslational modifications. As a preview of the actual symposium, the present discussion is an attempt to enumerate cases of cofactor involvement in these different categories: 1) essential nutrients as participants in posttranslational modifications; 2) cofactors as donor substrates in reversible, regulatory modifications; and 3) cofactor incorporation or generation as covalent constituents of proteins. The actual symposium topics are taken from category 1: vitamin C and protein hydroxylation (K. I. Karivikkio) and vitamin K and protein carboxylation (J. W. Suttie) and category 3: biotinylation (H. G. Wood), phycobiliproteins (A. Glazer), and pyruvoyl enzymes (W. Dowhan).

Animals↗
PubMed1987

The effects of ozone on lung, heart, and liver superoxide dismutase and glutathione peroxidase activities in the protein-deficient rat.

The effects of protein deficiency or food restriction and ozone exposure on lung, heart and liver superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were studied in weanling and adult rats. Two groups of rats were fed diets containing 4 or 16% protein. A third group was fed the 16% protein diet, but at the level consumed by the rats fed the 4% protein diet. After 3 weeks (weanling) or 5 weeks (adult), one-half of the rats in each group were exposed continuously to 0.64 ppm ozone for 7 days. In adult rat lung, O3 exposure typically stimulated Cu,Zn-SOD and GPx activities in all groups, but in weanling rats only GPx activity was elevated and only in rats fed the 16% protein diet. Liver Cu,Zn-SOD activity was also influenced by diet; in adult rats, liver Mn-SOD and GPx activities were often depressed following O3 exposure. Heart SOD and GPx, however, were not affected by ozone or diet. The pulmonary and hepatic effects due to diet and O3 further illustrate the importance of nutritional status when assessing the health effects of O3 exposure.

Animals↗
PubMed1986

Tropoelastin production and tropoelastin messenger RNA activity. Relationship to copper and elastin cross-linking in chick aorta.

The elastin content of the chick thoracic aorta increases 2--3-fold during the first 3 weeks post-hatching. The deposition of elastin requires the covalent cross-linking of tropoelastin by means of lysine-derived cross-links. This process is sensitive to dietary copper intake, since copper serves as cofactor for lysyl oxidase, the enzyme that catalyses the oxidative deamination of the lysine residues involved in cross-link formation. Disruption of cross-linking alters tissue concentrations of both elastin and tropoelastin and results in a net decrease in aortic elastin content. Autoregulation of tropoelastin synthesis by changes in the pool sizes of elastin or tropoelastin has been suggested as a possible mechanism for the diminished aortic elastin content. Consequently, dietary copper deficiency was induced to study the effect of impaired elastin cross-link formation on tropoelastin synthesis. Elastin in aortae from copper-deficient chicks was only two-thirds to one-half the amount measured in copper-supplemented chicks, whereas copper-deficient concentrations of tropoelastin in aorta were at least 5-fold higher than normal. In spite of these changes, however, increased amounts of tropoelastin, copper deficiency and decreased amounts of elastin did not influence the amounts of functional elastin mRNA in aorta. Likewise, the production of tropoelastin in aorta explants was the same whether the explants were taken from copper-sufficient or -deficient birds. The lower accumulation of elastin in aorta from copper-deficient chicks appeared to be due to extracellular proteolysis, rather than to a decrease in the rate of synthesis. Electrophoresis of aorta extracts, followed by immunological detection of tropoelastin-derived products, indicated degradation products in aortae from copper-deficient birds. In extracts of aortae from copper-sufficient chicks, tropoelastin was not degraded and appeared to be incorporated into elastin without further proteolytic processing.

Animals↗
PubMed1986

Role of plasma and serum proteases in the degradation of elastin.

Accelerated proteolysis of tropoelastin and elastin occurs in the major arteries of chicks fed copper-deficient diets. Signs of elastin degradation are not obvious in normal arteries of copper-supplemented chicks. It is proposed that the sources of proteases that effect elastin degradation are from plasma and serum. Both calcium-dependent proteases and kallikrein were effective in degrading tropoelastin and partially crosslinked insoluble elastin into peptides similar to those detected in aortic extracts from copper-deficient chicks. As dietary copper deficiency progresses it is also possible to detect elastin peptides in plasma.

Animals↗
PubMed1986

Lung collagen and elastin after ozone exposure in vitamin B-6-deficient rats.

The effects of vitamin B-6 deficiency and ozone exposure on selected features of connective tissue metabolism in lung were investigated in groups of weanling male rats fed one of three diets: B-6-supplemented, fed ad lib; B-6-deficient, fed ad lib; or B-6-supplemented, restricted to the food intake of deficient rats for 5 weeks. Also, perinatal rat pups were studied that were nursed from dams fed one of the 3 diets from parturition to day 15 of lactation. During the final week of each experiment, half of the rats in each of the groups were exposed to 0.64 ppm of ozone (23.5 h per day). The collagen and elastin content, collagen synthesis rate, total protein synthesis rate, and lysyloxidase activity of lungs were measured. Perinatal pups rendered vitamin B-6-deficient were particularly sensitive to ozone exposure (65% died as compared to fewer than 5% of the ad lib or food-restricted controls). When L-proline incorporation into collagen and total protein was investigated using lung minces, food restriction and B-6-deficiency resulted in about one-half the incorporation normally observed. Total lung lysyl oxidase activity was also decreased in B-6-deficient and food-restricted rats compared to B-6-supplemented rats fed ad lib. Exposure to ozone resulted in increased lysyl oxidase activity and collagen synthesis in lungs from B-6-supplemented rats, but such responses were not observed in B-6-deficient or food-restricted (FR) rats exposed to ozone.

Aging↗
PubMed1985

Effect of vitamin B-6 (pyridoxine) deficiency on lung elastin cross-linking in perinatal and weanling rat pups.

Weanling and perinatal rats were rendered vitamin B-6 (pyridoxine)-deficient. The rat pups were nursed from vitamin B-6-deficient or -sufficient dams and were killed at day 15 after parturition. The weanling rats were fed vitamin B-6-deficient or -sufficient diets and were killed after 5 weeks of treatment. Lung elastin from the groups of rats was then studied with respect to its content of lysine-derived cross-linking amino acids. Lung lysyl oxidase activity was also measured. B-6 deficiency decreased the number of lysine residues in elastin that were converted into the cross-linking amino acid precursor allysine. However, a more significant defect in cross-link formation was an apparent block in the condensation steps leading to the formation of desmosine. Desmosine was decreased, with an increase in the amounts of aldol condensation products (aldol CP) in elastin. It is proposed that the elevation in aldol CP results from the formation of thiazines, which are produced from the reaction between aldehyde and homocysteine. The concentration of homocysteine is significantly elevated in vitamin B-6-deficient rats.

Amino Acids↗
PubMed1985

Changes in response to ascorbic acid administered orally to rat pups: lung collagen, elastin and protein synthesis.

Rat pups were supplemented orally with high doses of L-ascorbic acid (AA) or D-isoascorbic acid (IA) throughout suckling. The regulation of AA in the lung and its relationship to collagen and elastin deposition were examined. Based on known responses of smooth muscle cells and fibroblasts in culture to high concentrations of AA, it was hypothesized that a markedly elevated intake of AA should increase net collagen deposition, but decrease net elastin deposition in the neonatal rat lung. In two experiments, groups of rat pups were gavaged daily with AA (in saline), in amounts corresponding to 0.1, 1 or 2% of the total consumed milk solids. As controls, pups were gavaged with IA (2% of the milk solids) or saline. The treatments were initiated 2 d postpartum and continued for 19 or 23 d. Compared to the saline-gavaged pups. AA and IA were elevated (twofold) in serum and lung at d 11, but not at d 25. Urinary excretion represented a major route for elimination of excess AA and IA. With respect to collagen and elastin accumulation, only elastin consistently was altered (10-20% decrease) in groups supplemented with AA or IA at the termination of experiments. The rodent appears to defend against elevation of AA concentration in the lung. Consequently, the putative effects of AA on the net deposition of lung collagen and elastin in vivo are less obvious than effects reported by others from in vitro studies.

Administration, Oral↗
PubMed1985

Effects of protein deficiency and food restriction on lung ascorbic acid and glutathione in rats exposed to ozone.

Weanling (52 +/- 4 g) or adult (259 +/- 16 g) male Sprague-Dawley rats were fed ad libitum casein-based diets containing 4 or 16% protein. A third group (food restricted) was fed daily the 16% protein diet, but at the food intake level of the 4% protein group. After 3 wk (weanling) or 5 wk (adults), half of the rats in each group were continuously exposed to 0.64 ppm ozone for 7 d. Ascorbic acid and reduced glutathione levels were then measured. In the heart and liver from weanling rats, ascorbic acid concentrations were lower in the protein-deficient group than in either control group. In the liver from weanling rats glutathione concentrations were also reduced in response to protein deficiency. Exposure to ozone produced no additional response. For adult rats the response for liver glutathione was similar to that of the weanlings. The liver ascorbate concentration, however, was consistently lower in adult rats compared to weanlings exposed to ozone. In lungs from adult rats, the ascorbic acid concentration was lower in the protein-deficient group than in either control group. On a whole-organ basis, both ascorbic acid and glutathione were usually higher in lungs from rats exposed to ozone than from those exposed to air. Interestingly, protein deficiency did not appear to compromise the lung's ability to maintain, in relative terms, the ascorbic acid or glutathione concentration in response to ozone.

Aging↗