Showing papers by "Rowett Research Institute published in 1993"

The single cell gel electrophoresis assay (comet assay): A European review

Abstract: The single cell gel electrophoresis (SCGE) assay is a rapid, simple, visual and sensitive technique for measuring DNA breakage in individual mammalian cells. Here we review the development of the SCGE assay (with particular reference to the alkaline version), existing protocols for the detection and analysis of comets, the relevant underlying principles determining the behaviour of DNA, and the potential applications of the technique.

Direct enzymic detection of endogenous oxidative base damage in human lymphocyte DNA

Abstract: The endogenous production of oxidative damage in DNA by free radicals released as a by-product of respiration is a likely cause of mutations which, if they occur in appropriate genes, may lead to cancer. Using an endonuclease specific for oxidized pyrimidines, in conjunction with the highly sensitive method of single cell gel electrophoresis, we have detected significant oxidative damage in untreated, freshly isolated lymphocytes from normal, healthy individuals.

Polyamines in food—implications for growth and health☆

Abstract: Different types of food (fruits, vegetables, meat, and milk products) were analyzed by high pressure liquid chromatography to determine their polyamine (putrescine, spermidine, and spermine) contents. All foods contained some polyamines, although the concentrations in different individual food components were variable. As was established earlier using 14C-labeled putrescine, spermidine, and spermine, polyamines are readily taken up by the gut and enter the systemic circulation. Food appears to constitute a major source of polyamines for humans and animals. The distribution of polyamines in the body, as determined by measuring the accumulation of 14C-spermidine in different tissues of the rat, was correlated with the metabolic activity and growth of particular organs. Thus, phytohemagglutinin induced both extensive hyperplastic growth and the preferential accumulation of labeled spermidine in the gut. Correspondingly, when skeletal muscle growth was promoted by the β-antagonist, clenbuterol, 14C-spermidine was sequestered by the hind leg gastrocnemius muscle. It is concluded that food polyamines are not only necessary for normal body metabolism, but are also used and directed preferentially to tissues and organs that have been stimulated to grow by metabolic signals.

Evaluation of bone turnover in type I osteoporosis using biochemical markers specific for both bone formation and bone resorption

Abstract: The aims of the study were to evaluate the use of bone-specific biochemical markers of turnover in type I osteoporosis, to test for evidence of heterogeneity of bone turnover in this condition, and to attempt to devise an ‘uncoupling index’ by using the relationship between bone-specific biochemical markers of bone formation and bone resorption. In women with type I osteoporosis (mean age 64 years, SD 5;n=63) the mean level of serum osteocalcin, a specific biochemical marker of bone formation, was 9.9 ng/ml (SD 2.0), which was higher than the level in normal postmenopausal women (mean age 65 years, SD 6;n=8.9 ng/ml (SD 2.0;p<0.01). The variance of serum osteocalcin levels in the two groups was similar. Compared with this 11% increase in the biochemical marker for bone formation, the markers of bone resorption, total urinary deoxypyridinoline (bone-specific), pyridinoline and hydroxyproline were increased by 40% (p<0.0001), 61% (p<0.0001) and 25% (p<0.01), respectively. Furthermore, these biochemical markers of bone resorption had greater variance in women in type I osteoporosis than in the normal postmenopausal women (p<0.001). The urinary excretion of the free crosslinks deoxypyridinoline, pyridinoline and glycosylated pyridinoline were increased by 26% (p<0.001), 17% (p<0.01) and 13% (NS) respectively. An ‘uncoupling index’ was calculated for the difference between urinary deoxypyridinoline and serum osteocalcin using the results from the normal women and expressed asz-scores. We conclude that the pyridinium crosslinks of collagen enable better discrimination between normal and osteoporotic women than does hydroxyproline. In osteoporosis there appears to be heterogeneity of bone resorption. Finally, an uncoupling index indicated that in osteoporosis bone resorption was increased to a greater extent than bone formation as compared with normal postmenopausal women.

A comparison of gas production during incubation with rumen contents in vitro and nylon bag degradability as predictors of the apparent digestibility in vivo and the voluntary intake of hays

Abstract: Ten hays harvested at three stages (early bloom MB, mid bloom MB or in seed) made from lucerne (Medicago sativaj, sweet clover (Melilotus segetalis), Persian clover (Trifolium resupinatum) and pre-bloom (PB) Italian ryegrass (Lolium multiflorum var.), were offered ad libitum to four Merino male sheep and daily intake (g dry matter (DM) per kg M0·75) and DM apparent digestibility (DMD) were measured. In sacco DM degradation (g per 100 g DM), gas production (ml per 200 mg DM), in vitro digestibility and fibre composition (g/kg DM) of the hays were also studied. Gas production or DM degradation were calculated at 6, 12, 24, 48, 72 or 96 h and their kinetics were described using the equation p = a + b(1 - e-ct). Intake and in vivo DMD of the hays were variable (P 0·05) related to animal performance. Between 12 and 96 h incubation, intake and in vivo DMD were better related to DM degradation (r = 0·79 to 0·83; r = 0·61 to 0·77) than to gas production (r = 0·73 to 0·80; r = 0·58 to 0·78). Prediction of intake and in vivo DMD from the (a + b) values did not provide a great advantage over using some of the static values of gas production or DM degradation.Multiple regression using separated kinetics of degradation resulted in highest accuracy for predicting intake and apparent digestibility from gas production (R2 = 0·63; R2 = 0·78) and nylon bag degradability (R2 = 0·77; R2 = 0·89). It was concluded that the gas test has good potentiality as it was capable of predicting not only apparent digestibility, but also intake to a level close to that of the nylon bag technique.

A bifunctional enzyme, with separate xylanase and beta(1,3-1,4)-glucanase domains, encoded by the xynD gene of Ruminococcus flavefaciens.

Abstract: Adjacent regions of a Ruminococcus flavefaciens 17 DNA fragment were found to encode xylanase and beta(1,3-1,4)-glucanase activities Sequencing of this fragment showed that both activities are encoded by a single 2,406-bp open reading frame corresponding to the xynD gene The predicted product has a characteristic signal sequence that is followed by an amino-terminal domain related to family G xylanases, while the carboxyterminal domain is related to beta(1,3-1,4)-glucanases from several other bacterial species These two domains are connected by a region of unknown function that consists of 309 amino acids and includes a 30-amino-acid threonine-rich sequence A polypeptide having a molecular weight of approximately 90,000 and exhibiting xylanase and beta(1,3-1,4)-glucanase activities was detected in Escherichia coli cells carrying the cloned xynD gene This is one of the first cases in which a microbial polysaccharidase has been shown to carry separate catalytic domains active against different plant cell wall polysaccharides within the same polypeptide xynD is one of a family of related genes in R flavefaciens that encode enzymes having multiple catalytic domains, and the amino terminus of XYLD exhibits a high degree of similarity with the corresponding regions of another xylanase, XYLA, which carries two different xylanase catalytic domains

Clenbuterol, a β-adrenoceptor agonist, increases relative muscle strength in orthopaedic patients

Abstract: 1 The sympathomimetic agent clenbuterol has a muscle-specific anabolic effect in normal and wasted muscles from animals This trial was designed to examine the effect of the drug on the recovery of muscle strength and area after open medial meniscectomy 2 A double-blind, completely randomized, placebo-controlled study was carried out on 20 healthy male patients Muscle strength and cross-sectional area were determined before and after surgery Patients were treated with drug or placebo for 4 weeks postoperatively and there was a 2 week washout period 3 The results suggest that, in the operated leg, clenbuterol treatment is associated with a more rapid rehabilitation of strength in knee extensor muscles; in the unoperated leg, knee extensor strength increased above the initial values after 6 weeks (P = 001) However, in terms of absolute strength the differences were not significant between the two groups 4 It is concluded that the data lend support to the proposition that clenbuterol has therapeutic potential in the treatment of muscle-wasting conditions

Antinutritive effects of wheat-germ agglutinin and other N-acetylglucosamine-specific lectins

Abstract: Incorporation of N-acetylglucosamine-specific agglutinins from wheat germ (Triticum aestivum; WGA), thorn apple (Datura stramonium) or nettle (Urtica dioica) rhizomes in the diet at the level of 7 g/kg reduced the apparent digestibility and utilization of dietary proteins and the growth of rats, with WGA being the most damaging. As a result of their binding and endocytosis by the epithelial cells of the small intestine, all three lectins were growth factors for the gut and interfered with its metabolism and function to varying degrees. WGA was particularly effective; it induced extensive polyamine-dependent hyperplastic and hypertrophic growth of the small bowel by increasing its content of proteins, RNA and DNA. Furthermore, an appreciable portion of the endocytosed WGA was transported across the gut wall into the systemic circulation, where it was deposited in the walls of the blood and lymphatic vessels. WGA also induced the hypertrophic growth of the pancreas and caused thymus atrophy. Although the transfer of the gene of WGA into crop plants has been advocated to increase their insect resistance, as the presence of this lectin in the diet may harm higher animals at the concentrations required to be effective against most pests, its use in plants as natural insecticide is not without health risks for man.

Metabolic consequences of intestinal parasitism.

Abstract: Clinical and subclinical intestinal parasitism is characterized by impaired production (Sykes & Coop, 1976; Steele, 1978) with poor growth rates in young animals and loss of body weight in older animals. Sheep also incur severe reductions in wool growth. A number of comprehensive reviews prepared over the last decade characterize and contrast the magnitude of such impairment across a range of intestinal roundworms and consider the factors which contribute to this problem (Armour & Ogbourne, 1982; Bremner, 1982; Sykes, 1983; Holmes, 1986; Parkins & Holmes, 1989; Poppi et al. 1990). Laboratory-based experiments designed to investigate the aetiology of different infections have followed two distinct approaches. They have involved administration of either a massive single dose of parasite larvae (e.g. 30 000-100 000; Steele, 1972; Roseby, 1973), or smaller doses of larvae given daily, or perhaps two to three times per week, in a so-called ‘trickle infection’ approach (Sykes & Coop, 1976; Jones & Symons, 1982). The latter regimen was adopted to more closely simulate the way animals incur infestation under practical conditions and it has provided a clearer picture of the aetiology and the subsequent immunological resistance which accompanies any subclinical condition. It has also shown the way in which the severity of infection relates to dose rate of larvae and nutritional state of the animal. As the present review will address mainly the metabolic consequences of subclinical parasitism, it will relate predominantly to experimental data obtained from animals subjected to ‘trickle infection’, mainly with the intestinal roundworm Trichostrongylus colubriformis, where very few clinical symptoms other than parasite eggs in the faeces and high eosinophil counts in the blood are seen.

Regulation of the ovine intestinal Na+/glucose co-transporter (SGLT1) is dissociated from mRNA abundance

Abstract: We have investigated the mechanisms of regulation of the Na+/glucose co-transporter (SGLT1) in a ruminant animal, which is an exceptional model system for studying intestinal glucose transport. Pre-ruminant lambs absorb glucose, produced by hydrolysis of the milk sugar lactose, in the intestine via apical SGLT1 and basolateral facilitative glucose transporters (GLUT2). Weaning coincides with the development of the rumen, and consequently the amount of hexoses reaching the small intestine of the ruminant sheep is undetectable. During development, SGLT1 activity and abundance in intestinal brush-border membranes decreased by over 200-fold, and either maintaining lambs on a milk replacer diet or infusing sheep intestine with D-glucose restored co-transporter activity and expression. We have measured ovine intestinal SGLT1 mRNA levels during development, with changes in diet and after direct infusion of D-glucose or methyl alpha-D-glucopyranoside into the intestinal lumen, in order to determine the level of regulation. During development, mRNA levels decreased only 4-fold. Lambs maintained on a milk replacer diet showed no change in mRNA levels relative to age-matched controls. Finally, upon infusion of the intestine of the ruminant sheep with sugars, D-glucose infusion increased SGLT1 mRNA, but only by 2-fold, compared with a 60-90-fold increase in co-transporter number and activity. Since the change in Na(+)-dependent glucose transport activity is correlated with SGLT1 protein abundance, and since changes in mRNA levels do not account for the dramatic changes in protein abundance, we conclude that the principal level of SGLT1 regulation by luminal sugar is translational or post-translational.

Kidney bean lectin‐induced Escherichia coli overgrowth in the small intestine is blocked by GNA, a mannose‐specific lectin

Abstract: The reversible and dose-dependent hyperplastic growth of the small intestine and accelerated epithelial cell turnover caused by feeding rats with diets containing kidney bean lectin (PHA) increased the proportion of immature cells on the villi whose membrane and/or cytoplasm contained mainly simple, polymannosylated glycans. These new alpha-linked mannosyl terminals, particularly of the damaged epithelium, facilitated the preferential adherence of opportunistic Escherichia coli with mannose-sensitive Type 1 fimbriae, and other coliforms, to the glycocalyx. Accordingly, the growth of the gut was accompanied by a reversible and PHA dose-dependent overgrowth with E. coli. As expected from their common carbohydrate specificity, the inclusion in the diet of the mannose-specific agglutinin from snowdrop (Galanthus nivalis) bulbs (GNA) significantly reduced the extent of E. coli overgrowth, but abolished neither the growth nor the damage caused by PHA to the small intestine. Thus, GNA and perhaps other mannose-specific lectins, especially when used in a preventive mode, can be used to specifically block the proliferation of Type 1 E. coli in the small intestine.

Accretion of total protein and individual amino acids by organs and tissues of growing lambs and the ability of nitrogen balance techniques to quantitate protein retention

Abstract: Twelve Suffolk-Finn Dorset lambs were reared from 25 to 40 or 25 to 55 kg body weight on either pelleted dried grass or a ration of pelleted grass plus barley (ratio 1:1) in a comparative slaughter experiment designed to determine the amounts of total nitrogen and individual amino acids accreted in different body components during growth. Nitrogen (N) balance measurements were determined frequently during this growth phase and accumulated N retentions were compared with the total N accretion determined by comparative slaughter. Total N and individual amino acids accumulated in carcass, wool, skin, offal and blood, head and feet, gastro-intestinal tract and liver were linearly related to body weight in all cases other than for cysteine in carcass. At 25 kg live weight, proportionately 0·52 of total body N was in carcass components, 0·115 in wool, 0·08 in skin, 0·10 in offal and blood, 0·095 in head and feet, 0·06 in the gastro-intestinal tract and 0·02 in liver. However as the animals grew from 25 to 55 kg, 0·256 of the total N accretion was in wool, which was rich in cysteine (98 g/kg total amino acid). Carcass accretion represented only 0·449 of total body N accretion. The N balance technique overestimated net protein accretion by 0·24 (s.e. 0·036).

The use of degradation characteristics of browse plants to predict intake and digestibility by goats

Abstract: Twenty-five male goats weighing 16 (s.e. 1-5) kg and aged 15 months were used to measure the dry matter (DM) intake of five browse species namely Acacia albida, Tamarindus indica, Etanda africana, Anogeissus leiocarpus and Sterculia setigera in a growth trial lasting 16 weeks. This was followed by a digestion trial with five goats in a 5 × 5 Latin square with 10 days adaptation and a 5-day measurement period. The degradation characteristics of the browse were measured by incubating samples in nylon bags for 6, 24, 48 and 96 h in the rumens of three sheep fitted with rumen cannulae and given hay plus grass nuts. The exponential model P = a +b(l — ect) was fitted to the data. Rumen fluid from the sheep was also used as an inoculum to incubate the samples in vitro for 3, 6,12, 24, 48, 72 and 96 h. Nylon bag degradability results were compared with in vivo results and in vitro gas production. The mean DM intakes, apparent digestible DM intakes and growth rates were 0·60, 0·62, 0·55, 0·53 and 0·65 kg/day, 0·43, 0·43, 0·35, 0·34 and 0·49 kg/day and 55, 60, 49, 42 and 62 glday for A. albida, T. indica, E. africana, A. leiocarpus and S. setigera respectively. Using the degradation characteristics A, B and c in a multiple regression analysis, the correlation coefficients with DM intake, apparent DM digestibility, apparent digestible DM intake and growth rate were 0·99, 0·88, 0·92 and 0·99 respectively. The inclusion of a lag phase (L) instead of A in the regression analysis improved the prediction of apparent DM digestibility and apparent digestible DM intake. The correlation coefficients between DM loss in nylon bags and in vitro gas production at 6, 24 and 48 h incubation were 0·84, 0·83 and 0·90 respectively. The results indicate that it may be possible to predict DM and apparent digestible DM intakes of browse by goats from the rumen degradation characteristics.

Dietary lectins are metabolic signals for the gut and modulate immune and hormone functions

Abstract: Although it is common knowledge that some dietary lectins can adversely affect the growth and health of young animals and that, therefore, lectins are implicated in nutritional disorders of the digestive system, it has not been rigorously established that findings with animals are also directly applicable to humans. However, because the glycosylation state of the human gut is basically similar to that of higher animals, it may be confidently predicted that the effects of dietary lectins will have similarities in both humans and animals. The more recent but not generally appreciated realization that lectins also have many beneficial effects on the gut and metabolism of animals makes the exploration of these for possible use in medical-clinical practice even more attractive. Most lectins in our diet are resistant to breakdown during gut passage and are bound and endocytosed by epithelial cells. These lectins are powerful exogenous growth factors for the small intestine, can induce dramatic shifts in its bacterial flora and interfere with its hormone secretion. In addition, lectins which are transported across the gut wall into the systemic circulation can modulate the body's hormone balance, metabolism and health. Although these physiological effects are mediated or reinforced by immune responses, they are primarily the result of the specific chemical reactivity of lectins with cell surface receptors of the gut. Clearly, as the interactions between lectins and the gut are predictable and may be manipulated to our advantage, the exciting scientific challenge is now to explore the possible transfer of the existing knowledge gained from animal experimentation to medical-clinical practice.

The role of propionate and acetate in the control of food intake in sheep

Abstract: Sheep fed ad lib . on a good-quality pelleted diet (g/kg; hay 500, barley 300, molasses, fish meal and minerals) were infused via the hepatic portal vein with mixtures of the sodium salts of volatile fatty acids, acetate and propionate, and a variety of equivalent osmotic loads. Propionate infused at rates between 0·6 and 2·5 mmol/min consistently reduced food intake in a linear, dose-related manner. Propionate infusions resulted in consistent dose-related increases in peripheral venous plasma glucose concentration but variable changes in insulin concentration. Infusion of osmotically balanced mixtures of propionate, acetate, mannitol or saline (9 g NaCI/I) indicated that at constant osmotic loading propionate caused a greater reduction in intake than other infusions. Acetate infusions only depressed food intake when administered as a 1 M solution. Lower concentrations had little effect, similar to that of equivalent osmotic loads of mannitol or saline. It is concluded that portal propionate flow has a potential role in the control of food intake in ruminants which is independent of osmotic effects or changes in plasma insulin concentration.

Changes with maturity in fibre composition and levels of extractable polyphenols in Greek browse: effects on in vitro gas production and in sacco dry matter degradation

Abstract: Neutral and acid detergent fibre (NDF, ADF), lignin, crude protein (CP), total extractable phenols (TEPH), tannins (TETa), condensed tannins (vanillin assay TECTa; proanthocyanidins TEPAs) in the leaves of spring Phyllirea media (SPRG) or early summer (ESUM) and early autumn (EAUT) Carpinus duinensis, Quercus coccifera and Fraxinus ornus were studied. Gas production (in vitro) and dry matter (DM) degradation (in sacco) were also studied after incubation for up to 96 h. Concentrations of TEPH, TETa, TECTa, TEPAs and the fibre components were variable (P 0·05). Concentrations of phenolics were related negatively but more significantly to gas production than to DM degradation (in sacco). Therefore, the gas test was considered to be more efficient than the nylon bag technique for the identification of feeds with antinutritive factors. Based on their phenolic content and gas production or DM degradation, the nutritive value of P media = F ornus (ESUM and EAUT) > C duinensis = Q coccifera (ESUM) > C duinensis = Q coccifera (EAUT). It was concluded that the decline in CP with maturity could make nitrogen the factor limiting intake and digestibility. This would be accentuated with an increase in the concentration of phenolics, particularly tannins.

The control of chondrocyte differentiation during endochondral bone growth in vivo: changes in TGF-beta and the proto-oncogene c-myc.

Abstract: The expression of transforming growth factor-beta and the c-myc proto-oncogene was studied in situ in the chondrocytes of the tibial growth plate of normal chicks and those with avian tibial dyschondroplasia in which the chondrocytes are developmentally arrested in the transitional phase between proliferation and differentiation This results in an accumulation of unmineralised and avascular cartilage Dyschondroplastic chicks showed reduced c-myc expression in the transitional chondrocytes but unaltered levels in the proliferating chondrocytes Transforming growth factor-beta expression was reduced in the transitional chondrocytes of dyschondroplastic chicks In areas where the lesion was being repaired there was evidence of increased expression of both c-myc protein and transforming growth factor-beta Addition of 1,25-dihydroxyvitamin D to the diet, which is known to reduce the incidence of dyschondroplasia, resulted in an increase in c-myc production These results suggest that both transforming growth factor-beta and the proto-oncogene c-myc may be important elements of the cascade of events that lead to chondrocyte differentiation, hypertrophy and mineralisation

The newly extended maize internode: A model for the study of secondary cell wall formation and consequences for digestibility

Abstract: The upper five internodes were collected from maize (Zea mays L) inbred cell lines Co 125 and W401 harvested at the same developmental stage, 5 days after silking. Each internode was dissected into ten equal lengths labelled A (top) to J (base). The youngest cells were found in section J, which contained the intercalary meristem, and the oldest in section A. Internodes 1, 3 and 5 provided material for chemical analysis and internodes 2 and 4 for degradability measurements. Cell wall material accounted for one-third of dry matter in section J, doubling to two-thirds in the upper half of each internode. Only section J exhibited a polysaccharide profile typical of primary cell walls. In all other sections, 1,4-linked glucose (± 46% of cell wall) and xylan largely free from side chains (± 25% of cell wall) predominated. Net accretion of cell wall polysaccharide reached a maximum by segment G and thereafter little additional carbohydrate was deposited. Lignification appeared to be separated from the biogenesis of structural carbohydrate and continued over much of each internode reaching a maximum in section C. Degradability measurements, made using a modified neutral-detergent cellulase digestibility method, showed substantial differences between sections. In line Co 125, cell wall degradability fell from over 95% in the youngest section (J) to approximately 24% in section B. Internode 4 of line W401 failed to show the same pattern of degradabilities, probably because of a sequential rather than simultaneous pattern of internode elongation. Saponifiable p-coumaric acid appeared to provide a more sensitive marker than lignin of the extent of secondary wall development. The inverse relationship between extent of lignification in each section and its degradability confirmed the value of the internode model for the study of secondary wall formation and its biological consequences.

Pancreatic Enlargement Is Evident in Rats Fed Diets Containing Raw Soybeans (Glycine max) or Cowpeas (Vigna unguiculata) for 800 Days but Not in Those Fed Diets Based on Kidney Beans (Phaseolus vulgaris) or Lupinseed (Lupinus angustifolius)

Abstract: Pancreatic weights and composition were studied with rats fed diets containing raw legume seeds for up to 800 d. Rapid pancreatic enlargement was induced by dietary soybeans (Glycine max) (high Kunitz and Bowman-Birk trypsin inhibitor contents, moderate lectin content) during the initial 150 d. Over the next 200 d the rate of pancreatic growth was similar to that in controls. After 350 d a second period of rapid pancreatic growth occurred. Macroscopic pancreatic nodules were evident in a number of rats fed soybeans for 500 d or more. A similar pattern of pancreatic growth was observed in rats fed dietary cowpeas (Vigna unguiculata) (high Bowman-Birk inhibitor content, low lectin content). Extensive pancreatic growth was also found in young rats fed moderate dietary levels of kidney beans (Phaseolus vulgaris) (low Bowman-Birk inhibitor content, high lectin content). However, the trophic effects diminished with time, and from 100 d onwards, little enlargement was evident. Consumption of a lupinseed (Lupinus angustifolius) diet (low trypsin inhibitor, low lectin content) did not cause pancreatic enlargement. The initial pancreatic growth induced by dietary soybeans seemed to be due to the lectins and trypsin inhibitors, whereas the second period of pancreatic growth was possibly due primarily to the trypsin inhibitors.

Physiological variations in the urinary excretion of pyridinium crosslinks of collagen

Abstract: To further validate measurements of the pyridinium crosslinks of collagen as indices primarily of bone resorption in arthritis and other diseases, the effects of day-to-day and nyctohemeral parallel variations, and of renal impairment have been studied. Day-to-day variations measured over 3 weeks were between 16 and 24% for a group of post-menopausal women. Nyctohemeral variations in crosslink excretion of 10-15% were recorded. Although crosslink excretion relative to creatinine was generally higher in the morning than in the evening, no consistent pattern was observed between healthy male and female volunteers and a group of patients with OA or RA. For patients with impaired renal function, with or without arthritis, there was no correlation between crosslink excretion and either creatinine clearance rates or urinary N-acetyl glucosaminidase activity. These results suggested that there was no direct relationship between renal function, at the glomerular or tubular level, and crosslink excretion.