Effect of Targeted Cytokine Inhibition on Progression of Post-Traumatic Osteoarthritis Following Intra-Articular Fracture

Intra-articular fractures (IAF) result in significant and prolonged inflammation, increasing the chances of developing post-traumatic osteoarthritis (PTOA). Interleukin-one beta (IL-1β) and Tumor Necrosis Factor-alpha (TNF-α) are key inflammatory factors shown to be involved in osteochondral degradation following IAF. As such, use of targeted biologics such as Infliximab (INX), a TNF-α inhibitor, and Anakinra (ANR), an interleukin-one (IL-1) receptor antagonist (IL1RA), may protect against PTOA by damping the inflammatory response to IAF and reducing osteochondral degradation. To test this hypothesis, IAFs were induced in the hindlimb knee joints of rats treated with INX at 10 mg/kg/day, ANR at 100 g/kg/day, or saline (vehicle control) by subcutaneous infusion for a period of two weeks and healing was evaluated at 8-weeks post injury. Serum and synovial fluid (SF) were analyzed for soluble factors. In-vivo microcomputed tomography (µCT) scans assessed bone mineral density and bone morphometry measurements. Cationic CA4+ agent assessed articular cartilage composition via ex vivo µCT. Scoring according to the Osteoarthritis Research Society International (OARSI) guidelines was performed on stained histologic tibia sections at the 56-day endpoint on a 0-6 scale. Systemically, ANR reduced many pro-inflammatory cytokines and reduced osteochondral degradation markers Cross Linked C-Telopeptide Of Type II (CTXII, p < 0.05) and tartrate-resistant acid phosphatase (TRAP, p < 0.05). ANR treatment resulted in increased chemokines; macrophage-chemotractant protein-1 (MCP-1), MPC-3, macrophage inhibitory protein 2 (MIP2) with a concomitant decrease in proinflammatory interleukin-17A (IL17A) at 14 days post-injury within the SF. Microcomputed tomography (µCT) at 56 days post-injury revealed ANR Treatment decreased epiphyseal degree of anisotropy (DA) (p < 0.05) relative to saline. No differences were found with OARSI scoring but contrast-enhanced µCT revealed a reduction in glycosaminoglycan content with ANR treatment. These findings suggest targeted cytokine inhibition, specifically IL-1 signaling, as a monotherapy has minimal utility for improving IAF healing outcomes but may have utility for promoting a more permissive inflammatory environment that would allow more potent disease modifying osteoarthritis drugs to mitigate the progression of PTOA after IAF.

Development and characterization of an intra-articular fracture mediated model of post-traumatic osteoarthritis

PURPOSE

This study aimed to develop and characterize a closed intra-articular fracture (IAF) mediated post-traumatic osteoarthritis (PTOA) model in rats to serve as a testbed for putative disease modifying interventions.

METHODS

Male rats were subject to a 0 Joule (J), 1 J, 3 J, or 5 J blunt-force impact to the lateral aspect of the knee and allowed to heal for 14 and 56 days. Micro-CT was performed at time of injury and at the specified endpoints to assess bone morphometry and bone mineral density measurements. Cytokines and osteochondral degradation markers were assayed from serum and synovial fluid via immunoassays. Histopathological analyses were performed on decalcified tissues and assessed for evidence of osteochondral degradation.

RESULTS

High-energy (5 J) blunt impacts consistently induced IAF to the proximal tibia, distal femur, or both while lower energy (1 J and 3 J) impacts did not. CCL2 was found to be elevated in the synovial fluid of rats with IAF at both 14- and 56-days post-injury while COMP and NTX-1 were upregulated chronically relative to sham controls. Histological analysis showed increased immune cell infiltration, increased osteoclasts and osteochondral degradation with IAF relative to sham.

CONCLUSION

Based on results from the current study, our data indicates that a 5 J blunt-forced impact adequately and consistently induces hallmark osteoarthritic changes to the articular surface and subchondral bone at 56 days after IAF. Marked development of PTOA pathobiology suggest this model will provide a robust testbed for screening putative disease modifying interventions that might be translated to the clinic for militarily relevant, high-energy joint injuries.

Effects of Adjunct Antifibrotic Treatment within a Regenerative Rehabilitation Paradigm for Volumetric Muscle Loss

The use of a rehabilitation approach that promotes regeneration has the potential to improve the efficacy of pro-regenerative therapies and maximize functional outcomes in the treatment of volumetric muscle loss (VML). An adjunct antifibrotic treatment could further enhance functional gains by reducing fibrotic scarring. This study aimed to evaluate the potential synergistic effects of losartan, an antifibrotic pharmaceutical, paired with a voluntary wheel running rehabilitation strategy to enhance a minced muscle graft (MMG) pro-regenerative therapy in a rodent model of VML. The animals were randomly assigned into four groups: (1) antifibrotic with rehabilitation, (2) antifibrotic without rehabilitation, (3) vehicle treatment with rehabilitation, and (4) vehicle treatment without rehabilitation. At 56 days, the neuromuscular function was assessed, and muscles were collected for histological and molecular analysis. Surprisingly, we found that the losartan treatment decreased muscle function in MMG-treated VML injuries by 56 days, while the voluntary wheel running elicited no effect. Histologic and molecular analysis revealed that losartan treatment did not reduce fibrosis. These findings suggest that losartan treatment as an adjunct therapy to a regenerative rehabilitation strategy negatively impacts muscular function and fails to promote myogenesis following VML injury. There still remains a clinical need to develop a regenerative rehabilitation treatment strategy for traumatic skeletal muscle injuries. Future studies should consider optimizing the timing and duration of adjunct antifibrotic treatments to maximize functional outcomes in VML injuries.

The relationships among gender, perceived financial barriers to care, and health status in a rural population

This study examined the relationships among gender, perceived financial barriers to health care, and selected health status indicators in a randomly selected rural Appalachian sample. The data were gathered through the Johnson County Health Survey. The survey was conducted through personal interviews with 207 females and 178 males representing 197 households. The Duke Health Profile was used to measure the perceived health of the respondents. Analysis of variance, t tests, and descriptive statistics were used to analyze the data. Analysis of the data revealed that women perceive financial barriers to health care significantly more than men (P < 0.01), even when living in the same household; women had significantly poorer health than men (P < 0.01); and both women and men with perceived financial barriers experienced poorer health (P < 0.01) than those who did not perceive such barriers. Conclusions from the study suggest that in this rural sample women were the most compromised by both gender and health status, and that they perceived that their health care needs were not being adequately met.

Nurse-managed primary care in a rural community. Outcomes of five years of practice

Nursing centers offer underserved populations affordable access to primary health care. But to build their case for inclusion in managed care plans and the health care delivery systems of the future, they must document their successes.

Interdisciplinarity: the story of a journey

Everywhere we turn, interdisciplinarity has become a key concept guiding health care education and practice. Granting agencies call for it. Educational and health policy makers extol its virtues. Accreditation agencies across health disciplines recommend it as a competency for the present and future. But what is it? How do we get it from our educational and practice systems that are compartmentalized by claims to discipline-specific knowledge, tradition, and the flow of dollars from funding sources? What is it like after we do get it? And most of all, why would we ever want it in the first place? We have had some significant experience within our Division of Health Sciences in interdisciplinary teaching, practice, and scholarship. Our experience was initially framed by implementation of one of the seven W.K. Kellogg Foundation Community Partnerships for Health Professions Education grants. The grant brought the education of medical, nursing, and other health professions students out of the hospital to interdisciplinary primary care experiences in and with the community. We will never tell you we have a straightforward prescription for success. Living interdisciplinarity, like living life itself, is something that frequently poses more questions than it answers. We will, with enthusiasm, share with you what we have learned in our unique journey together in hopes that you and your colleagues will find something useful for your own voyage into interdisciplinarity.

A comprehensive primary health care delivery model

Primary health care has emerged as a key element in the health care delivery system. A well-organized system of primary care is needed to reduce the fragmented, often parallel approaches currently seen in the delivery of health care. Important aspects of primary care include not only comprehensive services and continuity of care to the individual client but health assessment and intervention to meet the community needs as a whole. A nursing model is presented for comprehensive interdisciplinary primary health care practice, education, and research. A unique aspect of this model is the partnership with the community, which is an essential component for operationalization of the model. Use of this model will provide an opportunity for cost-effective, acceptable, accessible, and holistic health care that better meets the needs of the community.

Cloning of two different 5' untranslated exons of bovine acidic fibroblast growth factor by the single strand ligation to single-stranded cDNA methodology

In an attempt to characterize the 5' UTR of the aFGF mRNAs we used the new anchored PCR methodology, single strand ligation to ss-cDNAs (SLIC). In bovine brain and retina, two kinds of aFGF cDNA clones were isolated. They contained two alternative exons located 34 bp upstream to the translation initiation codon ATG. Taking into account the number of clones specific for each exon, the two mRNAs are expressed with the same ratio in both tissues. One of these bovine 5' UTR exons (136 bp) showed 81% identity to a human 5' UTR exon, the second one (323 bp) was 70% identical to the second human 5' UTR exon with a central region of 90 nucleotides showing 41% identity. The conservation of the splicing positions for these 5' UTR alternate exons in both bovine and human species, suggests that the overall structure of the aFGF gene is conserved in mammals. Furthermore, the conservation of the nucleotide sequences and of the localization of these 5' UTR exons suggests that these non-coding regions may be involved in the control of aFGF gene expression.

Optimized Spectrophotometric Determination of Aldehyde Dehydrogenase Activity in Erythrocytes

We describe a reliable and sensitive semiautomated spectrophotometric assay of aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity in erythrocytes. The hemolysate can be stabilized with sucrose, and the technique involves only microliters of hemolysate on a centrifugal analyzer. The use of microcolumns to remove interfering hemoglobin is avoided, and reproducibility of the assay has been improved by manipulating the inherent lactate dehydrogenase activity of erythrocytes by adding lactate and oxalate to the reaction mixture. These modifications have decreased the analytical imprecision of the assay, allowing a better appraisal of aldehyde dehydrogenase activity in erythrocytes as a biological marker of excess alcohol consumption. Erythrocytic ALDH activity was significantly less in 40 alcoholics than in 145 teetotallers (median activity 128 vs 219 mU/g of hemoglobin, respectively; P = 0.0001), indicating the potential of this assay as a useful marker of excess alcohol consumption.

Promoter elements of the rat choline acetyltransferase gene allowing nerve growth factor inducibility in transfected primary cultured cells

Choline acetyltransferase, the enzyme responsible for the synthesis of acetylcholine, provides a convenient index for cholinergic neurons. Using a previously identified rat cDNA clone, we have isolated several corresponding genomic clones and have characterized a 1,902-bp fragment that contains part of the first noncoding exon as well as promoter sequences. The promoter activity of this fragment was tested, taking advantage of the recently developed lipopolyamine-mediated DNA transfer method, which allows transfection of primary neurons. The 1,902-bp sequence drives the expression of the bacterial chloramphenicol acetyltransferase (CAT) reporter gene in a culture of dissociated cells prepared from the septal area of fetal (embryonic day 17) rats, a structure rich in cholinergic neurons. Moreover, addition of nerve growth factor to the culture increases CAT expression by approximately 56-fold, indicating that our DNA fragment contains sequences required for NGF induction. In addition, it contains consensus sequences for various transcription factors, including those of the basic helix-loop-helix family. Finally, experiments to characterize the transcription start site are presented.

Optimized spectrophotometric determination of aldehyde dehydrogenase activity in erythrocytes

We describe a reliable and sensitive semiautomated spectrophotometric assay of aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity in erythrocytes. The hemolysate can be stabilized with sucrose, and the technique involves only microliters of hemolysate on a centrifugal analyzer. The use of microcolumns to remove interfering hemoglobin is avoided, and reproducibility of the assay has been improved by manipulating the inherent lactate dehydrogenase activity of erythrocytes by adding lactate and oxalate to the reaction mixture. These modifications have decreased the analytical imprecision of the assay, allowing a better appraisal of aldehyde dehydrogenase activity in erythrocytes as a biological marker of excess alcohol consumption. Erythrocytic ALDH activity was significantly less in 40 alcoholics than in 145 teetotallers (median activity 128 vs 219 mU/g of hemoglobin, respectively; P = 0.0001), indicating the potential of this assay as a useful marker of excess alcohol consumption.

Oligodeoxyribonucleotide ligation to single-stranded cDNAs: a new tool for cloning 5' ends of mRNAs and for constructing cDNA libraries by in vitro amplification

Cloning full length cDNAs is a difficult task especially if mRNAs are not abundant or if tissue is only available in limited amounts. Current strategies are based on in vitro amplification of cDNAs after adding a homopolymeric tail at the 3' end of the ss-cDNA. Since subsequent amplification steps yield unspecific amplified DNA mostly due to non-specific annealing of the reverse primer containing a homopolymeric tail, we have devised a new strategy based on the ligation of single-stranded oligodeoxyribonucleotide to the 3' end of single-stranded cDNAs. The efficiency of the strategy was assessed by analyzing the 5' ends of the rat pineal gland tryptophan hydroxylase messenger. The 5' end of the least abundant messenger (0.005% of total mRNAs) could be cloned without selection. Sixty percent of the analyzed clones correspond to TPH. This technique revealed a 5-nt stretch not apparent using dG tailing strategy. The potentiality of the method for generating cDNAs libraries was tested with 10(4) PC12 cells. In this library, the abundance of tyrosine hydroxylase clones (0.03%) correlated well with the abundance of the corresponding messenger, showing that no major distortion was introduced into the construction of the library.

Ultralow volume application of organophosphate concentrate in grain terminals: a new occupational health hazard

The introduction of ultralow volume (ULV) application of the organophosphate pesticide Fenitrothion in grain terminals presents a risk to workers of skin contact with concentrate. Blood testing, by the Ellman method, of a group of five grain terminal workers working on grain treatment showed a lowering of mean red blood cell cholinesterase (RBC ChE) activity to 23 units/gm Hb (normal value 28-40) with a range of 16-29. The probable cause was identified as percutaneous absorption of Fenitrothion concentrate by workers using ungloved hands to clean blocked drip feed nozzles. Modification of work practices was followed by a rise of mean RBC ChE to 33.6 units/gm Hb (range 32-36) during the following grain treatment season. RBC ChE activity measured during the intervening winter season--that is, a non-exposure period--showed a mean of 33.3 units/gm Hb (range 23-40).

Human prostatic acid phosphatase: properties of the native enzyme, and the enzyme-antibody complex

Acid phosphatase purified from human prostatic tissue was shown to be homogeneous by polyacrylamide gel electrophoresis and N-terminal amino acid analysis. However, isoelectric focusing revealed a large number of isoenzymes which were reduced to four by digestion with neuraminidase. It is suggested that the patterns observed are due to differences in bound carbohydrate attached to the same protein backbone. Antiserum to the purified enzyme was produced in rabbits and reacted with the enzyme to form an enzymatically active complex of large molecular weight. This complex is more stable at high temperatures than the native enzyme. Kinetic analysis of both the enzyme and the enzyme-antibody complex demonstrated that the binding of the antibody caused no significant change to the active site of the enzyme.

Urinary oxalate determination by use of immobilized oxalate oxidase in a continuous-flow system

In this procedure, oxalate oxidase (EC 1.2.3.4) immobilized in a continuous-flow system is used to determine oxalate in urine. The hydrogen peroxide formed from oxalate is detected by use of a color reaction with peroxidase (EC 1.11.1.7), 3-methyl-2-benzothiazoline hydrazine, and N,N-dimethylalanine. However, urine contains an oxalate oxidase inhibitor, which cannot be removed by heating, ion-exchange resins, or cellulose columns. This makes it necessary to precipitate the oxalate before assay. The overall assay system is accurate (oxalate recovery, 95.9%), sensitive (less than or equal to 5 mumol/L), precise (within-batch CV less than 1.25%, between-batch CV less than 5%), and relatively rapid (60 samples per working day). The assay system has better accuracy than an established chemical method and a gas-chromatographic method, and is considerably less arduous than and correlates well (r = 0.94) with a modified chemical method. The reference interval for urinary oxalate excretion is 0.16-0.56 mmol per day (n = 97). Only nonphysiological concentrations of ascorbate interfere with the assay, by increasing the oxalate result in the overall assay, presumably by post-micturition formation of oxalate from ascorbate in the urine samples.

Urinary oxalate determination by use of immobilized oxalate oxidase in a continuous-flow system

In this procedure, oxalate oxidase (EC 1.2.3.4) immobilized in a continuous-flow system is used to determine oxalate in urine. The hydrogen peroxide formed from oxalate is detected by use of a color reaction with peroxidase (EC 1.11.1.7), 3-methyl-2-benzothiazoline hydrazine, and N,N-dimethylalanine. However, urine contains an oxalate oxidase inhibitor, which cannot be removed by heating, ion-exchange resins, or cellulose columns. This makes it necessary to precipitate the oxalate before assay. The overall assay system is accurate (oxalate recovery, 95.9%), sensitive (less than or equal to 5 mumol/L), precise (within-batch CV less than 1.25%, between-batch CV less than 5%), and relatively rapid (60 samples per working day). The assay system has better accuracy than an established chemical method and a gas-chromatographic method, and is considerably less arduous than and correlates well (r = 0.94) with a modified chemical method. The reference interval for urinary oxalate excretion is 0.16-0.56 mmol per day (n = 97). Only nonphysiological concentrations of ascorbate interfere with the assay, by increasing the oxalate result in the overall assay, presumably by post-micturition formation of oxalate from ascorbate in the urine samples.

Preparation and characterization of a human serum matrix suitable for quality control or reference materials

We describe the preparation of a human serum based matrix suitable for inclusion in long-term control materials. The procedure entails the removal of cells, fibrin and lipoproteins from blood to produce a clear, stable material which has been stored frozen at -70 degrees C for up to 14 mth without any apparent deterioration. When incorporated into a quality control material, storage at 4 degrees and -20 degrees C may cause a change in several unstable constituents, but the material remains optically clear. A noticeable reduction in lipoprotein as a result of the preparative procedure is probably responsible for the continued clarity of the matrix. The nature of the matrix has been examined by polyacrylamide gel electrophoresis and does not reveal any unusual protein bands, whereas commercially available materials when similarly examined often reveal protein bands not present in normal serum. The matrix has been used to prepare control material for the Chemical Pathology Quality Assurance Programme Group of the Royal College of Pathologists of Australasia/Australian Association of Clinical Biochemists.

Models for the metabolic production of oxalate from xylitol in humans: a role for fructokinase and aldolase

It has been proposed previously that oxalate precursors may be formed in the transketolase reaction during the metabolism of xylitol. It is shown in this paper that fructokinase and aldolase, purified from human liver, provide an alternative model in that, in coupled sequence, they produce glycolaldehyde, an oxalate precursor, from D-xylulose via D-xylulose 1-phosphate; D-fructose does not give rise to glycolaldehyde. It is concluded that metabolic pathways based on a combination of the transketolase, fructokinase and aldolase reactions can account for the production of glucose, lactate, tetronates (C-threonic and D-erythronic acids) and oxalate (precursors) during the metabolism of xylitol administered parenterally.

A mechanism for the thiamin-sparing action of dietary xylitol in the rat

The changes induced by dietary xylitol in the gastrointestinal tract of the rat were investigated in relation to the phenomenon of vitamin-sparing. Within 18 days of consuming a synthetic diet, deficient in thiamin, riboflavin and pyridoxine, rats ceased to grow and began to lose weight rapidly. If xylitol was then included in the diet (10% w/w), the effect of the vitamin-deficient diet on growth was reversed. Moreover, within 3 days of the rats ingesting xylitol, the metabolism of this sugar polyol by the caecal microflora was increased 17-fold and the caecal concentrations of thiamin and thiamin pyrophosphate were increased 5-fold. Increases were also observed in the caecal size, the weight of the caecal contents, and the weight of the caecal wall. In contrast to the rapid changes observed within the caecum, liver thiamin pyrophosphate levels did not rise until 6-12 days after the feeding of xylitol, at which time the rats had begun to gain weight. The caecal contents were shown to contain facultative bacteria which have the ability to metabolise and grow on xylitol and which can, at the same time, synthesise thiamin. Species of the genera Klebsiella, Serratia and Micrococcus which have this ability were isolated from the caecal contents of rats. It is assumed that coprophagy is the means by which the thiamin and other vitamins synthesised by enteral bacteria become available to the host, although some absorption from the caecum cannot be excluded.

Creatine kinase

Creatine kinase is present in significant concentrations in skeletal muscle and cardiac muscle and to a lesser extent in gastrointestinal tract and brain tissue. The enzyme has been purified from a variety of tissues and an examination of its kinetic and physical properties reveal that the enzyme consists of two subunits and can exist as three isoenzymes containing essential cysteine residues. These properties are important in understanding its stability, the assay conditions, and the techniques used to identify the different isoenzymes. The relationship between the properties and the determination of the enzyme in biological fluids will be a main thrust of the review. Creatine kinase activity in serum rises rapidly in conditions such as acute myocardial infarction and trauma to skeletal muscle. However, the interpretation of such increases is dependent upon a sound knowledge of the factors which influence both the total and isoenzyme activities. The nature of these factors will be discussed in detail.

Oxidized copper wire particles for copper therapy in sheep

Ninety Merino weaner sheep were assigned to one of six groups on the basis of liveweight and liver copper concentrations. Sheep in four groups each received one oral dose of oxidized copper wire particles, viz. 2.5, 5, 10 or 20 g per animal. Sheep in another group each received a subcutaneous injection of 12 mg copper as diethylamino cupro-oxyquinoline sulfonate and another group of sheep did not receive any copper supplement. Liver copper concentrations responded positively to copper oxide load. The 2.5 g dose of copper oxide wire was more efficacious than the commercial injectable product in raising copper status, but the higher doses of oxide raised liver copper concentrations to values similar to those recorded in cases of copper poisoning. Copper concentrations in blood plasma, muscle and kidney were not altered by the copper load. No clinical signs, nor biochemical or histological evidence of acute copper toxicity, were found. Liver copper values fell in all sheep from 10 weeks after copper therapy until the end of the trial at 50 weeks post-therapy. Over this period of 40 weeks, the rate of mobilization of liver copper was linear and was positively related to the initial concentration of copper in the liver. A significant proportion of the oxidized copper wire dosed to sheep was recovered in the forestomachs and abomasa of selected sheep 4 weeks after dosing. No evidence of abomasal damage due to particles could be established. It is concluded that oral dosing of oxidized copper wire is a safe and effective method of copper supplementation to sheep.

The effect of dietary xylitol on the ability of rat caecal flora to metabolise xylitol

The effect of dietary xylitol on the ability of the rat caecal flora to metabolise xylitol was investigated. Xylitol metabolism in micro-organisms has generally been assessed in terms of pH change and acid production which are often insensitive in demonstrating low rates of substrate utilisation. Using a rapid and sensitive radioisotopic assay, in which 14CO2 production from [U-14C] xylitol was measured, it was possible to show that the caecal microflora obtained from rats can metabolise xylitol. This activity was increased 10, 15, 30 and 40-fold in the caecal flora taken from rats fed diets containing 2.5,5,10 and 20% xylitol, respectively. Using the caecal microflora of normally fed rats, the order of 14CO2 production from 14C-labelled sugars and sugar alcohols was glucose greater than fructose greater than xylose greater than sorbitol greater than or equal to xylitol. The feeding of glucose and fructose did not alter the 14CO2 producing activities, whereas xylose feeding increased xylose metabolism, sorbitol feeding increased sorbitol and xylitol metabolism, xylitol feeding increased sorbitol, xylose and its own metabolism and arabitol feeding increased xylose and sorbitol metabolism. Marked changes were also observed in the population of the caecal flora of xylitol-fed rats, with increases in the number of gram-positive bacteria, compared to rats on a normal diet. Possible mechanisms for these effects involve mutation, selection of micro-organisms capable of metabolising sugar alcohols, and the induction of enzymes involved in sugar alcohol metabolism.

Some biochemical studies on the adaptation associated with xylitol ingestion in rats

The mechanism of adaptation to dietary carbohydrates was investigated by examining cellular metabolism in the liver and gut lumen. The inclusion of 10% (w/w) glucose, fructose, sucrose, xylose, sorbitol, xylitol or arabitol in the diet of rats for 7 days had essentially no effect on the ability of liver homogenates to produce 14CO2 from labelled glucose, fructose, xylose, sorbitol or xylitol. Moreover, no major changes were observed in the activities of hepatic enzymes. In these studies, diarrhoea and caecal distension were only observed in those rats receiving dietary sugar alcohols. Rats were also fed 0, 2.5, 5, 10, and 20% (w/w) xylitol in their diets for periods ranging from 1 to 14 days. These diets caused no significant changes in 16 of the commonly assessed blood parameters which included liver function tests. Xylitol feeding, however, caused distension, caecal gas production, decreases in the pH of caecal contents, the appearance of a fluffy layer in the centrifuged specimens of caecal contents, and diarrhoea. These changes were directly related to the concentration of xylitol in the caecal contents. After various periods, and depending on the concentration of xylitol in the diet, the rats underwent an adaptation which reduced the incidence of diarrhoea. In the short term, dietary xylitol does not affect the function of the liver or the gut wall, but causes an adaptation within the gut microflora. This adaptation leads to the increased ability of gut microflora to utilise xylitol, followed by a subsequent reduction in the caecal osmotic load and diarrhoea.

Metabolic and cardiovascular side effects of the beta 2-adrenoceptor agonists salbutamol and rimiterol

The metabolic and cardiovascular side-effects of intravenous infusions of therapeutic doses of beta 2-adrenoceptor agonists salbutamol and rimiterol have been determined in four healthy male subjects. There were dose-related increases in plasma glucose, renin activity, serum insulin and heart rate, and significant hyperlactataemia and ketonaemia. There were dose-related decreases in plasma potassium, phosphate and corticosteroids and significant hypocalcaemia and hypomagnesaemia. The effects of equivalent molar amounts of salbutamol and rimiterol were similar. Whichever drug is used, special care is required with patients who may have abnormal glucose tolerance, potassium depletion, or be predisposed to lactic acidosis. Rimiterol may be preferable for infusion because of its short plasma half-life.

Increased creatine kinase activities associated with haemolysis

The effect of haemolysis on creatine kinase activity has been investigated. The presence of adenylate kinase released from erythrocytes increases the apparent creatine kinase activity. This can be overcome by the addition of 10 mumol/l of diadenosine pentaphosphate to the reagents.

The production of (14C) oxalate during the metabolism of (14C) carbohydrates in isolated rat hepatocytes

Oxalate (14C) was produced during the metabolism of (U-14C) carbohydrates in hepatocytes isolated from normal rats. At 10 mM, the order of oxalate production was fructose > glycerol > xylitol > sorbitol greater than or equal to glucose in the ratio 10 : 4 : 3 : 1 : 1. This difference between oxalate production from fructose and glucose was reflected in their rates of utilisation, glucose being poorly metabolised in hepatocytes from fasted rats. Fructose was rapidly metabolised, producing glucose, lactate and pyruvate as the major metabolites. Glycerol, xylitol and sorbitol were metabolised at half the rate of fructose, the major metabolites being glucose, lactate and glycerophosphate. The marked similarity in the pattern of intermediary metabolites produced by these polyols was not, however, reflected in the rates of oxalate production. Hepatic polyol metabolism resulted in high levels of cytosolic NADH, as indicated by elevated lactate : pyruvate and glycerophosphate : dihydroxyacetone phosphate ratios. The artificial electron acceptor, phenazine methosulphate (PMS) stimulated oxalate production from the polyols, particularly xylitol. In the presence of PMS, the order of oxalate production was fructose greater than or equal to xylitol > glycerol > sorbitol in the ratio 10 : 10 : 6 : 2. The production of glucose, lactate and pyruvate from the polyols was also stimulated by PMS, whereas the general metabolism of fructose, including oxalate production, was little affected. Oxalate (14C) was produced from (1-14C), (2-14C) and (6-14C) but not (3,4-14C) glucose in hepatocytes isolated from non-fasted, pyridoxine-deficient rats. Whilst this labelling pattern is consistent with oxalate being produced by a number of pathways, it is suggested that metabolism via hydroxypyruvate is a major route for oxalate production from various carbohydrates, with perhaps the exception of xylitol, which appears to have an alternative mechanism for oxalate production. The observation that carbohydrates, particularly fructose, contribute to endogenous oxalate production lends support to the hypothesis that a high sucrose consumption contributes to the formation of renal oxalate stones in man.

Nalidixic acid and lactic acidosis

Nalidixic acid may cause severe acidosis and we report a fatal case of lactic acidosis assocaited with nalidixic acid therapy. Studies in normal volunteers showed drug related impairment of lactate metabolism. We question whether the drug should be used in patients who may accumulate the drug or be predisposed to lactic acidosis.

Oxalate excretion in rats injected with xylitol or glycollate: stimulation by phenobarbitone pre-treatment

The hypothesis that the prior intake of barbiturates may predispose patients to form increased amounts of oxalate following the intravenous infusion of xylitol was investigated in the rat. Phenobarbitone pre-treatment resulted in a 2-3 fold increase in urinary [14C] oxalate concentration following the intraperitoneal injection of [U-14C] xylitol or [l -14C] glycollate. The absence of any marked changes in urine volumes and creatinine excretion implied that this increase in urinary oxalate excretion was due to the enhanced synthesis of oxalate. The activities of key enzymes in hepatic oxalate synthesis, glycollate oxidase, lactate dehydrogenase, catalase and alanine aminotransferase were not altered by phenobarbitone pre-treatment. It is suggested that the increased activity of the microsomal mixed function oxidases, following phenobarbitone treatment, may facilitate the oxidation of glycollate and possibly xylitol. This communication leads experimental support to the concept that the prior intake of drugs, such as barbiturates, may predispose patients to form increased amounts of oxalate.

Plasma lactate dehydrogenase activity will be increased if detergent and platelets are present

Plasma lactate dehydrogenase activity is artifactually increased when analyzed on the SMAC (Technicon) continuous-flow analyzer. The factors responsible are incomplete centrifugation and the presence of detergent in the dilution buffer. The contribution of platelet lactate dehydrogenase in the plasma is demonstrated with a case of thrombocytosis.

Plasma lactate dehydrogenase activity will be increased if detergent and platelets are present

Plasma lactate dehydrogenase activity is artifactually increased when analyzed on the SMAC (Technicon) continuous-flow analyzer. The factors responsible are incomplete centrifugation and the presence of detergent in the dilution buffer. The contribution of platelet lactate dehydrogenase in the plasma is demonstrated with a case of thrombocytosis.

Formation of oxalate in pyridoxine or thiamin deficient rats during intravenous xylitol infusions

Glucose, fructose, sorbitol and xylitol were assessed as precursors of oxalate in normal rats and rats deficient in thiamin or vitamin B-6. Urinary excretions of oxalate, glyoxylate and glycine were increased significantly in vitamin B-6 deficient rats infused with xylitol when compared with all other groups. Using [U-14C]xylitol, oxalate was shown to be derived directly from this polyalcohol in vitamin B-6 deficient rats. These results suggest that vitamin B-6 deficiency may be a factor contributing to oxalate crystal deposition seen in some patients infused with xylitol.