The effects of endogenously- and exogenously-induced hyperketonemia on exercise performance and adaptation

Elevating blood ketones may enhance exercise capacity and modulate adaptations to exercise training; however, these effects may depend on whether hyperketonemia is induced endogenously through dietary carbohydrate restriction, or exogenously through ketone supplementation. To determine this, we compared the effects of endogenously- and exogenously-induced hyperketonemia on exercise capacity and adaptation. Trained endurance athletes undertook 6 days of laboratory based cycling ("race") whilst following either: a carbohydrate-rich control diet (n = 7; CHO); a carbohydrate-rich diet + ketone drink four-times daily (n = 7; Ex Ket); or a ketogenic diet (n = 7; End Ket). Exercise capacity was measured daily, and adaptations in exercise metabolism, exercise physiology and postprandial insulin sensitivity (via an oral glucose tolerance test) were measured before and after dietary interventions. Urinary β-hydroxybutyrate increased by ⁓150-fold and ⁓650-fold versus CHO with Ex Ket and End Ket, respectively. Exercise capacity was increased versus pre-intervention by ~5% on race day 1 with CHO (p < 0.05), by 6%-8% on days 1, 4, and 6 (all p < 0.05) with Ex Ket and decreased by 48%-57% on all race days (all p > 0.05) with End Ket. There was an ⁓3-fold increase in fat oxidation from pre- to post-intervention (p < 0.05) with End Ket and increased perceived exercise exertion (p < 0.05). No changes in exercise substrate metabolism occurred with Ex Ket, but participants had blunted postprandial insulin sensitivity (p < 0.05). Dietary carbohydrate restriction and ketone supplementation both induce hyperketonemia; however, these are distinct physiological conditions with contrasting effects on exercise capacity and adaptation to exercise training.

Abnormal whole-body energy metabolism in iron-deficient humans despite preserved skeletal muscle oxidative phosphorylation

Iron deficiency impairs skeletal muscle metabolism. The underlying mechanisms are incompletely characterised, but animal and human experiments suggest the involvement of signalling pathways co-dependent upon oxygen and iron availability, including the pathway associated with hypoxia-inducible factor (HIF). We performed a prospective, case-control, clinical physiology study to explore the effects of iron deficiency on human metabolism, using exercise as a stressor. Thirteen iron-deficient (ID) individuals and thirteen iron-replete (IR) control participants each underwent 31P-magnetic resonance spectroscopy of exercising calf muscle to investigate differences in oxidative phosphorylation, followed by whole-body cardiopulmonary exercise testing. Thereafter, individuals were given an intravenous (IV) infusion, randomised to either iron or saline, and the assessments repeated ~ 1 week later. Neither baseline iron status nor IV iron significantly influenced high-energy phosphate metabolism. During submaximal cardiopulmonary exercise, the rate of decline in blood lactate concentration was diminished in the ID group (P = 0.005). Intravenous iron corrected this abnormality. Furthermore, IV iron increased lactate threshold during maximal cardiopulmonary exercise by ~ 10%, regardless of baseline iron status. These findings demonstrate abnormal whole-body energy metabolism in iron-deficient but otherwise healthy humans. Iron deficiency promotes a more glycolytic phenotype without having a detectable effect on mitochondrial bioenergetics.

β-Hydroxybutyrate Oxidation in Exercise Is Impaired by Low-Carbohydrate and High-Fat Availability

Purpose: In this study, we determined ketone oxidation rates in athletes under metabolic conditions of high and low carbohydrate (CHO) and fat availability. Methods: Six healthy male athletes completed 1 h of bicycle ergometer exercise at 75% maximal power (WMax) on three occasions. Prior to exercise, participants consumed 573 mg·kg bw^-1 of a ketone ester (KE) containing a ¹³C label. To manipulate CHO availability, athletes undertook glycogen depleting exercise followed by isocaloric high-CHO or very-low-CHO diets. To manipulate fat availability, participants were given a continuous infusion of lipid during two visits. Using stable isotope methodology, β-hydroxybutyrate (βHB) oxidation rates were therefore investigated under the following metabolic conditions: (i) high CHO + normal fat (KE+CHO); (ii) high CHO + high fat KE+CHO+FAT); and (iii) low CHO + high fat (KE+FAT). Results: Pre-exercise intramuscular glycogen (IMGLY) was approximately halved in the KE+FAT vs. KE+CHO and KE+CHO+FAT conditions (both p < 0.05). Blood free fatty acids (FFA) and intramuscular long-chain acylcarnitines were significantly greater in the KE+FAT vs. other conditions and in the KE+CHO+FAT vs. KE+CHO conditions before exercise. Following ingestion of the ¹³C labeled KE, blood βHB levels increased to ≈4.5 mM before exercise in all conditions. βHB oxidation was modestly greater in the KE+CHO vs. KE+FAT conditions (mean diff. = 0.09 g·min^-1, p = 0.03; d = 0.3), tended to be greater in the KE+CHO+FAT vs. KE+FAT conditions (mean diff. = 0.07 g·min^-1; p = 0.1; d = 0.3) and were the same in the KE+CHO vs. KE+CHO+FAT conditions (p < 0.05; d < 0.1). A moderate positive correlation between pre-exercise IMGLY and βHB oxidation rates during exercise was present (p = 0.04; r = 0.5). Post-exercise intramuscular βHB abundance was markedly elevated in the KE+FAT vs. KE+CHO and KE+CHO+FAT conditions (both, p < 0.001; d = 2.3). Conclusion: βHB oxidation rates during exercise are modestly impaired by low CHO availability, independent of circulating βHB levels.

Effects of acute nutritional ketosis during exercise in adults with glycogen storage disease type IIIa are phenotype-specific: An investigator-initiated, randomized, crossover study

Glycogen storage disease type IIIa (GSDIIIa) is an inborn error of carbohydrate metabolism caused by a debranching enzyme deficiency. A subgroup of GSDIIIa patients develops severe myopathy. The purpose of this study was to investigate whether acute nutritional ketosis (ANK) in response to ketone-ester (KE) ingestion is effective to deliver oxidative substrate to exercising muscle in GSDIIIa patients. This was an investigator-initiated, researcher-blinded, randomized, crossover study in six adult GSDIIIa patients. Prior to exercise subjects ingested a carbohydrate drink (~66 g, CHO) or a ketone-ester (395 mg/kg, KE) + carbohydrate drink (30 g, KE + CHO). Subjects performed 15-minute cycling exercise on an upright ergometer followed by 10-minute supine cycling in a magnetic resonance (MR) scanner at two submaximal workloads (30% and 60% of individual maximum, respectively). Blood metabolites, indirect calorimetry data, and in vivo ³¹ P-MR spectra from quadriceps muscle were collected during exercise. KE + CHO induced ANK in all six subjects with median peak βHB concentration of 2.6 mmol/L (range: 1.6-3.1). Subjects remained normoglycemic in both study arms, but delta glucose concentration was 2-fold lower in the KE + CHO arm. The respiratory exchange ratio did not increase in the KE + CHO arm when workload was doubled in subjects with overt myopathy. In vivo ³¹ P MR spectra showed a favorable change in quadriceps energetic state during exercise in the KE + CHO arm compared to CHO in subjects with overt myopathy. Effects of ANK during exercise are phenotype-specific in adult GSDIIIa patients. ANK presents a promising therapy in GSDIIIa patients with a severe myopathic phenotype. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT03011203.

Nutritional ketosis improves exercise metabolism in patients with very long-chain acyl-CoA dehydrogenase deficiency

A maladaptive shift from fat to carbohydrate (CHO) oxidation during exercise is thought to underlie myopathy and exercise-induced rhabdomyolysis in patients with fatty acid oxidation (FAO) disorders. We hypothesised that ingestion of a ketone ester (KE) drink prior to exercise could serve as an alternative oxidative substrate supply to boost muscular ATP homeostasis. To establish a rational basis for therapeutic use of KE supplementation in FAO, we tested this hypothesis in patients deficient in Very Long-Chain acyl-CoA Dehydrogenase (VLCAD). Five patients (range 17-45 y; 4 M/1F) patients were included in an investigator-initiated, randomised, blinded, placebo-controlled, 2-way cross-over study. Patients drank either a KE + CHO mix or an isocaloric CHO equivalent and performed 35 minutes upright cycling followed by 10 minutes supine cycling inside a Magnetic Resonance scanner at individual maximal FAO work rate (fatmax; approximately 40% VO₂ max). The protocol was repeated after a 1-week interval with the alternate drink. Primary outcome measures were quadriceps phosphocreatine (PCr), Pi and pH dynamics during exercise and recovery assayed by in vivo ³¹ P-MR spectroscopy. Secondary outcomes included plasma and muscle metabolites and respiratory gas exchange recordings. Ingestion of KE rapidly induced mild ketosis and increased muscle BHB content. During exercise at FATMAX, VLCADD-specific plasma acylcarnitine levels, quadriceps glycolytic intermediate levels and in vivo Pi/PCr ratio were all lower in KE + CHO than CHO. These results provide a rational basis for future clinical trials of synthetic ketone ester supplementation therapy in patients with FAO disorders. Trial registration: ClinicalTrials.gov. Protocol ID: NCT03531554; METC2014.492; ABR51222.042.14.

Aneurysms of the communicating segment of the internal carotid artery with posterior communicating artery agenesis are associated with perforator infarction after embolization

BACKGROUND

While anatomic features associated with the risk of posterior communicating artery (PcoA) occlusion after embolization of aneurysms of the PcoA segment of the internal carotid artery (ICA) are well known, the link between perforator origin and perforator infarction has only been reported following neurosurgical clipping. The aim of this study was to determine the origin of anterior thalamic perforators and correlate it with risk of perforator infarction after embolization of PcoA segment aneurysms.

METHODS

One-hundred-and-ninety consecutive patients treated for PcoA segment aneurysms between 2017 and 2019 were included. PcoA and anterior thalamic perforator origin anatomy was assessed with computed tomography (CT) angiography, digital subtracted angiography, and high-resolution three-dimensional rotational cone-beam CT angiography (CBCT-A) by two independent interventional neuroradiologists. The presence of perforator infarction after embolization was ascertained from the patient's notes and follow-up imaging.

RESULTS

CBCT-A was superior in demonstrating the origin of perforators (P<0.001). The prevalence of perforator origin was estimated at 86% (95% CI 81%-92%) for PcoA, 8% (95% CI 4%-13%) for aneurysm wall, and 5% (95% CI 2%-9%) for ICA. The aneurysm wall origin was exclusively associated with PcoA agenesis, as well as higher risk of perforator infarction after aneurysm coiling compared with other variants (OR=14, 95% CI 2-88, P=0.006).

CONCLUSIONS

Our study suggests that anterior thalamic perforators may arise from aneurysm wall when there is no PcoA. Anatomic association between PcoA agenesis and perforator arising from ICA could underlie such findings, and careful consideration is essential before aneurysm repair to anticipate the risk of thalamic infarction in such cases.

Nutritional Ketoacidosis During Incremental Exercise in Healthy Athletes

Purpose: Ketosis, achieved through ingestion of ketone esters, may influence endurance exercise capacity by altering substrate metabolism. However, the effects of ketone consumption on acid-base status and subsequent metabolic and respiratory compensations are poorly described.

Methods: Twelve athletically trained individuals completed an incremental bicycle ergometer exercise test to exhaustion following the consumption of either a ketone ester [(R)-3-hydroxybutyrate-(R)-1,3-butanediol] or a taste-matched control drink (bitter flavoured water) in a blinded, cross-over study. Respiratory gases and arterialised blood gas samples were taken at rest and at regular intervals during exercise.

Results: Ketone ester consumption increased blood D-β-hydroxybutyrate concentration from 0.2 to 3.7 mM/L (p < 0.01), causing significant falls versus control in blood pH to 7.37 and bicarbonate to 18.5 mM/L before exercise. To compensate for ketoacidosis, minute ventilation was modestly increased (p < 0.05) with non-linearity in the ventilatory response to exercise (ventilatory threshold) occurring at a 22 W lower workload (p < 0.05). Blood pH and bicarbonate concentrations were the same at maximal exercise intensities. There was no difference in exercise performance having consumed the ketone ester or control drink.

Conclusion: Athletes compensated for the greater acid load caused by ketone ester ingestion by elevating minute ventilation and earlier hyperventilation during incremental exercise.

Beyond RPE: The Perception of Exercise Under Normal and Ketotic Conditions

Aim

Subjective perceptions of exercising exertion are integral to maintaining homeostasis. Traditional methods have utilized scores of 'rating of perceived exertion' (RPE) to quantify these subjective perceptions, and here we aimed to test whether RPE may encompass identifiable localized perceptions from the lungs (breathlessness) and legs (leg discomfort), as well as their corresponding measures of anxiety. We utilized the intervention of ketoacidosis (via consumption of an exogenous ketone ester drink) to independently perturb exercise-related metabolites and humoral signals, thus allowing us to additionally identify the possible contributing physiological signals to each of these perceptions.

Methods

Twelve trained volunteers underwent two incremental bicycle ergometer tests to exhaustion, following ingestion of either an exogenous ketone ester or a taste-matched placebo drink. Cardiorespiratory measures, blood samples and perceived exertion scales were taken throughout. Firstly, two-way repeated-measures ANOVAs were employed to identify the overall effects of ketoacidosis, followed by generalized linear mixed model regression to isolate physiological predictors contributing to each perception.

Results

Rating of perceived exertion was found to contain contributions from localized perceptions of breathlessness and leg discomfort, with no measurable effect of ketoacidosis on overall exertion. Leg discomfort, anxiety of breathing and anxiety of leg discomfort were increased during ketoacidosis, and correspondingly contained pH within their prediction models. Anxiety of leg discomfort also encompassed additional humoral signals of blood glucose and ketone concentrations.

Conclusion

These results indicate the presence of localized components of RPE in the form of breathlessness and leg discomfort. Furthermore, subjective perceptions of anxiety appear to result from a complex interplay of humoral signals, which may be evolutionarily important when monitoring exertion under times of metabolic stress, such as during starvation.

A Ketone Ester Drink Lowers Human Ghrelin and Appetite

OBJECTIVE

The ketones d-β-hydroxybutyrate (BHB) and acetoacetate are elevated during prolonged fasting or during a "ketogenic" diet. Although weight loss on a ketogenic diet may be associated with decreased appetite and altered gut hormone levels, it is unknown whether such changes are caused by elevated blood ketones. This study investigated the effects of an exogenous ketone ester (KE) on appetite.

METHODS

Following an overnight fast, subjects with normal weight (n = 15) consumed 1.9 kcal/kg of KE, or isocaloric dextrose (DEXT), in drinks matched for volume, taste, tonicity, and color. Blood samples were analyzed for BHB, glucose, insulin, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide tyrosine tyrosine (PYY), and a three-measure visual analogue scale was used to measure hunger, fullness, and desire to eat.

RESULTS

KE consumption increased blood BHB levels from 0.2 to 3.3 mM after 60 minutes. DEXT consumption increased plasma glucose levels between 30 and 60 minutes. Postprandial plasma insulin, ghrelin, GLP-1, and PYY levels were significantly lower 2 to 4 hours after KE consumption, compared with DEXT consumption. Temporally related to the observed suppression of ghrelin, reported hunger and desire to eat were also significantly suppressed 1.5 hours after consumption of KE, compared with consumption of DEXT.

CONCLUSIONS

Increased blood ketone levels may directly suppress appetite, as KE drinks lowered plasma ghrelin levels, perceived hunger, and desire to eat.

On the Metabolism of Exogenous Ketones in Humans

Background and aims: Currently there is considerable interest in ketone metabolism owing to recently reported benefits of ketosis for human health. Traditionally, ketosis has been achieved by following a high-fat, low-carbohydrate "ketogenic" diet, but adherence to such diets can be difficult. An alternative way to increase blood D-β-hydroxybutyrate (D-βHB) concentrations is ketone drinks, but the metabolic effects of exogenous ketones are relatively unknown. Here, healthy human volunteers took part in three randomized metabolic studies of drinks containing a ketone ester (KE); (R)-3-hydroxybutyl (R)-3-hydroxybutyrate, or ketone salts (KS); sodium plus potassium βHB. Methods and Results: In the first study, 15 participants consumed KE or KS drinks that delivered ~12 or ~24 g of βHB. Both drinks elevated blood D-βHB concentrations (D-βHB C_max: KE 2.8 mM, KS 1.0 mM, P < 0.001), which returned to baseline within 3-4 h. KS drinks were found to contain 50% of the L-βHB isoform, which remained elevated in blood for over 8 h, but was not detectable after 24 h. Urinary excretion of both D-βHB and L-βHB was <1.5% of the total βHB ingested and was in proportion to the blood AUC. D-βHB, but not L-βHB, was slowly converted to breath acetone. The KE drink decreased blood pH by 0.10 and the KS drink increased urinary pH from 5.7 to 8.5. In the second study, the effect of a meal before a KE drink on blood D-βHB concentrations was determined in 16 participants. Food lowered blood D-βHB C_max by 33% (Fed 2.2 mM, Fasted 3.3 mM, P < 0.001), but did not alter acetoacetate or breath acetone concentrations. All ketone drinks lowered blood glucose, free fatty acid and triglyceride concentrations, and had similar effects on blood electrolytes, which remained normal. In the final study, participants were given KE over 9 h as three drinks (n = 12) or a continuous nasogastric infusion (n = 4) to maintain blood D-βHB concentrations greater than 1 mM. Both drinks and infusions gave identical D-βHB AUC of 1.3-1.4 moles.min. Conclusion: We conclude that exogenous ketone drinks are a practical, efficacious way to achieve ketosis.

On the Metabolism of Exogenous Ketones in Humans

Background and aims: Currently there is considerable interest in ketone metabolism owing to recently reported benefits of ketosis for human health. Traditionally, ketosis has been achieved by following a high-fat, low-carbohydrate "ketogenic" diet, but adherence to such diets can be difficult. An alternative way to increase blood D-β-hydroxybutyrate (D-βHB) concentrations is ketone drinks, but the metabolic effects of exogenous ketones are relatively unknown. Here, healthy human volunteers took part in three randomized metabolic studies of drinks containing a ketone ester (KE); (R)-3-hydroxybutyl (R)-3-hydroxybutyrate, or ketone salts (KS); sodium plus potassium βHB. Methods and Results: In the first study, 15 participants consumed KE or KS drinks that delivered ~12 or ~24 g of βHB. Both drinks elevated blood D-βHB concentrations (D-βHB C_max: KE 2.8 mM, KS 1.0 mM, P < 0.001), which returned to baseline within 3-4 h. KS drinks were found to contain 50% of the L-βHB isoform, which remained elevated in blood for over 8 h, but was not detectable after 24 h. Urinary excretion of both D-βHB and L-βHB was <1.5% of the total βHB ingested and was in proportion to the blood AUC. D-βHB, but not L-βHB, was slowly converted to breath acetone. The KE drink decreased blood pH by 0.10 and the KS drink increased urinary pH from 5.7 to 8.5. In the second study, the effect of a meal before a KE drink on blood D-βHB concentrations was determined in 16 participants. Food lowered blood D-βHB C_max by 33% (Fed 2.2 mM, Fasted 3.3 mM, P < 0.001), but did not alter acetoacetate or breath acetone concentrations. All ketone drinks lowered blood glucose, free fatty acid and triglyceride concentrations, and had similar effects on blood electrolytes, which remained normal. In the final study, participants were given KE over 9 h as three drinks (n = 12) or a continuous nasogastric infusion (n = 4) to maintain blood D-βHB concentrations greater than 1 mM. Both drinks and infusions gave identical D-βHB AUC of 1.3-1.4 moles.min. Conclusion: We conclude that exogenous ketone drinks are a practical, efficacious way to achieve ketosis.

The discovery of a potent Nav1.3 inhibitor with good oral pharmacokinetics

In this article, we describe the discovery of an aryl ether series of potent and selective Na_v1.3 inhibitors. Based on structural analogy to a similar series of compounds we have previously shown bind to the domain IV voltage sensor region of Na_v channels, we propose this series binds in the same location. We describe the development of this series from a published starting point, highlighting key selectivity and potency data, and several studies designed to validate Na_v1.3 as a target for pain.

Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes

Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.

Psychophysical Differences in Ventilatory Awareness and Breathlessness between Athletes and Sedentary Individuals

Purpose: Breathlessness is a complex set of symptoms that are comprised of both sensory and affective (emotional) dimensions. While ventilation is now understood to be a potential limiter to performance in highly-trained individuals, the contribution of breathlessness-anxiety in those nearing maximal ventilation during intense exercise has not yet been considered as a limiter to performance.

Methods: In this study, we compared the physiology and psychology of breathlessness in 20 endurance athletes with 20 untrained age- and sex-matched sedentary controls. Subjects completed baseline spirometry and anxiety questionnaires, an incremental exercise test to exhaustion and a steady-state hypercapnic ventilatory response test, with concurrent measures of breathlessness intensity and breathlessness-anxiety.

Results: Compared with sedentary subjects, athletes reported equivalent breathlessness intensity but greater breathlessness-anxiety at maximal exercise (athletes vs. sedentary (mean ± SD): breathlessness intensity (0–100%) 80.7 (22.7) vs. 72.5 (17.2), p = 0.21; breathlessness-anxiety (0–100%), 45.3 (36.3) vs. 22.3 (20.0), p = 0.02). Athletes operated at higher proportions of their maximal ventilatory capacity (MVV) (athletes vs. sedentary (mean ventilation ± SD; % MVV): 101.6 (27.2) vs. 73.7 (30.1), p = 0.003). In the athletes there was a positive linear correlation between ventilation and breathlessness score during the hypercapnic challenge that was not observed in the sedentary controls.

Conclusion: The results of this study indicate that whilst operating at high proportions of maximal ventilation, breathlessness-anxiety becomes increasingly prominent in athletes. Our results suggest that ventilatory perception pathways may be a target for improved athletic performance in some individuals.

The Population Pharmacokinetics of D-β-hydroxybutyrate Following Administration of (R)-3-Hydroxybutyl (R)-3-Hydroxybutyrate

The administration of ketones to induce a mild ketosis is of interest for the alleviation of symptoms associated with various neurological disorders. This study aimed to understand the pharmacokinetics (PK) of D-β-hydroxybutyrate (BHB) and quantify the sources of variability following a dose of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (ketone monoester). Healthy volunteers (n = 37) were given a single drink of the ketone monoester, following which, 833 blood BHB concentrations were measured. Two formulations and five dose levels of ketone monoester were used. A nonlinear mixed effect modelling approach was used to develop a population PK model. A one compartment disposition model with negative feedback effect on endogenous BHB production provided the best description of the data. Absorption was best described by two consecutive first-order inputs and elimination by dual processes involving first-order (CL = 10.9 L/h) and capacity limited elimination (V max = 4520 mg/h). Covariates identified were formulation (on relative oral bioavailable fraction and absorption rate constant) and dose (on relative oral bioavailable fraction). Lean body weight (on first-order clearance) and sex (on apparent volume of distribution) were also significant covariates. The PK of BHB is complicated by complex absorption process, endogenous production and nonlinear elimination. Formulation and dose appear to strongly influence the kinetic profile following ketone monoester administration. Further work is needed to quantify mechanisms of absorption and elimination of ketones for therapeutic use in the form of ketone monoester.

Acute nutritional ketosis: implications for exercise performance and metabolism

Ketone bodies acetoacetate (AcAc) and D-β-hydroxybutyrate (βHB) may provide an alternative carbon source to fuel exercise when delivered acutely in nutritional form. The metabolic actions of ketone bodies are based on sound evolutionary principles to prolong survival during caloric deprivation. By harnessing the potential of these metabolic actions during exercise, athletic performance could be influenced, providing a useful model for the application of ketosis in therapeutic conditions. This article examines the energetic implications of ketone body utilisation with particular reference to exercise metabolism and substrate energetics.

Structural and electronic properties of luminescent copper(I) halide complexes of bis[2-(diphenylphosphano)phenyl] ether (DPEphos). Crystal structure of [CuCl(DPEphos)(dmpymtH]

Heteroleptic copper(I) halide complexes containing the bis[2-(diphenylphosphano)phenyl]ether (DPEphos) ligand and the heterocyclic thioamides pyridine-2(1H)-thione (py2SH), pyrimidine-2(1H)-thione (pymtH) or 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH) have been synthesized and characterized by (1)H-NMR, IR spectroscopy, elemental analyses and melting point determinations. The complexes can be readily obtained by the addition of the thione ligand to a CuX-diphosphane adduct in dichloromethane-ethanol solution. The molecular structure of [CuCl(DPEphos)(dmpymtH)] complex has been established by single-crystal X-ray diffraction. The structure features a tetrahedral copper(I) center with two phosphorus atoms from the chelating diphos ligand, one halogen atom and the exocyclic sulfur atom of the heterocyclic thioamide unit. The complexes are strongly emissive in the solid state at ambient temperature. DFT and TD-DFT calculations were employed to study the structural, electronic and photophysical properties of the novel complexes. Electronic absorption spectra show two broad bands in the regions 275-290 and 380-398 nm of mixed MLCT/IL character. Intense blue-green emission is observed in the region 500-558 nm for complexes having py2SH or dmpymtH thione ligands. The emitting first triplet excited state, T(1) is mainly localized on the thione ligand.

Constrained total hip arthroplasty in a paediatric patient with cerebral palsy and painful dislocation of the hip. A case report

We describe a patient with cerebral palsy, of normal intelligence, who could not walk but who by the age of 16 had been successfully managed with a staged bilateral total hip arthroplasty using a constrained liner.

The unexpected formation of biologically active Cu(II) Schiff mono-base complexes with 2-thiophene-carboxaldehyde and dipropylenetriamine: crystal and molecular structure of CudptaSCl2

Two novel mononuclear Cu(II) coordination compounds of the type [Cu(dptaS)Cl(2)] and [Cu(dptaS)Br(2)] (dptaS=1,3-propanediamine, N(1)-[3-aminopropyl]-N(3)-[2-thienylmethylidene] or Schiff mono-base of dipropylenetriamine with 2-thiophene-carboxaldehyde) were prepared by the hydrolysis of the di-bases, [Cu(dptaSS)Cl(2)] and [Cu(dptaSS)Br(2)] (dptaSS=1,3-propanediamine, N(1)-[2-thienylmethylidene]-N(3)-[[2-thienylmethylidene]aminopropyl] or Schiff di-base of dipropylenetriamine with 2-thiophenecarboxaldehyde) to mono-bases with the release of one aldehyde molecule and freeing of the -NH(2) group of the coordinated dpta ligand. The X-ray determined structure of the compound [Cu(dptaS)Cl(2)] was confirmed by spectroscopic methods, magnetic and molar conductivity measurements. The Cu(II) atom is a five-coordinated CuN(3)Cl(2) chromophore with three nitrogen atoms coming up from the (dptaS) ligand and two chlorine atoms completing the square pyramidal geometry. Antiproliferative activity of both novel compounds was examined against a panel of different normal and cancer cell lines (MRC5, HeLa, MCF7, HT-29 and T47D) and showed that the Cu(II) Schiff mono-bases exhibit increased activity as compared to the starting materials. In vitro studies of plasmid DNA (pDNA) and double stranded DNA (dsDNA) interaction with the compounds under study support this difference. Some of the important factors contributing to the antiproliferative activity of the compounds under study, such as ionic character and dipole moment were also discussed in terms of the density functional theory calculated electronic structures of the ligands and their Cu(II) compounds.

Copper(II) Schiff base coordination compounds of dien with heterocyclic aldehydes and 2-amino-5-methyl-thiazole: synthesis, characterization, antiproliferative and antibacterial studies. Crystal structure of CudienOOCl2

A new series of coordination compounds of the starting materials [Cu(dienX(2)Y(2))] and their adducts [Cu(dienXXY(2))(2a-5mt)] (where dien=diethylenetriamine, dienXX=Schiff bases of diethylenetriamine with 2-furaldehyde or 2-thiophene-carboxaldehyde, X=O, S, Y=Cl, Br, NO(3) and 2a-5mt=2-amino-5-methylthiazole) were synthesized by stepwise reactions and their structures were established by C, H, N, Cu analysis, spectroscopic, magnetic and molar conductivity measurements. The isolated compounds are monomers, paramagnetic and electrolytic compounds of the type 1:1. In all cases, the pentadentate Schiff base (dienXX) is bonded in a tridentate fashion through the 3 N atoms. In the CudienXXY(2) compounds the coordination sphere is completed by two Cl or Br or NO(3) groups in a square pyramidal arrangement. The proposed structure for this type of compound was further supported by X-ray diffraction analysis of the compound [Cu(dienOO)Cl(2)]. Its basal plane consists of three Cu-N contacts [2.017(2), 2.025(2) and 2.012(2) A] from dienOO, and the Cl(1) atom, while the Cl(2) atom possesses the apical position, the relevant distances being 2.2732(7) A for Cu-Cl(1) and 2.6051(7) A Cu-Cl(2). In the CudienX(2)Y(2).2a-5mt adducts the coordination sphere of copper is further completed by the nitrogen ring atom of the 2a-5mt, forming an octahedral configuration. The study of the biological activity of the compounds synthesized against a panel of different normal and cancer cell lines (MRC5, HeLa, MCF7, HT-29, OAW42, T47D) and bacteria (E. coli, B. cereus, B. subtilis) showed that the adducts of the type [Cu(dienXXY(2))(2a-5mt)] exhibit increased activity both in cancer cells and in bacteria, compared to the starting material of type [Cu(dienXXY(2))].

Low temperature emission spectra of individual single-walled carbon nanotubes: multiplicity of subspecies within single-species nanotube ensembles

Low-temperature photoluminescence (PL) studies of individual semiconducting single-walled carbon nanotubes reveal ultranarrow peaks (down to 0.25 meV linewidths) that exhibit blinking and spectral wandering. Multiple peaks appear within bands previously assigned to nanotubes of certain chiralities, indicating the existence of numerous subspecies within single-chirality specimens. The sharp PL features show two types of distinctly different shapes (symmetric versus asymmetric) and temperature dependences (weak versus strong), which we attribute to the presence of unintentionally doped nanotubes along with undoped species.

Comparative studies on biological activities of Prunus padus and P. spinosa

Comparative studies on the antibacterial and free radical scavenging activities of the n-hexane, dichloromethane and methanol extracts of the seeds of Prunus padus and P. spinosa have been carried out. General toxicity of these extracts has also been determined.

Bioactivity of secoiridoid glycosides from Centaurium erythraea

As part of our on-going search for bioactive compounds from Scottish plants, two secoiridoid glycosides, swertiamarin and sweroside, have been isolated from the aerial parts of Centaurium erythraea Rafn (Family: Gentianaceae) by reversed-phase preparative HPLC coupled with a photo-diode-array detector. The structures of these compounds were elucidated unambiguously by UV, FABMS and extensive 1D and 2D NMR spectroscopic analyses and also by comparing experimental data with literature data. Antibacterial, free radical scavenging activities and general toxicity of these glycosides have been assessed. Both compounds inhibited the growth of Bacillus cereus, Bacillus subtilis, Citrobacter freundii and Escherichia coli. While swertiamarin was also active against Proteus mirabilis and Serratia marcescens, sweroside inhibited the growth of Staphylococcus epidermidis. Swertiamarin and sweroside exhibited significant general toxicity in brine shrimp lethality bioassay and the LD50 values were 8.0 microg/ml and 34 microg/ml, respectively, whereas that of the positive control podophyllotoxin, a well known cytotoxic lignan, was 2.79 microg/ml. Chemotaxonomic implications of these compounds in the family Gentianaceae have also been discussed briefly.

Biological activity of Euonymus europaeus

The n-hexane, dichloromethane and methanol extracts of the seeds of Euonymus europaeus have been screened for antibacterial and free radical scavenging activity. General toxicity (brine shrimp lethality assay) of these extracts has also been assessed.

Biological activity of Glechoma hederacea

The n-hexane, dichloromethane and methanol extracts of the aerial parts of Glechoma hederacea have been screened for antibacterial and free radical scavenging activity. General toxicity (brine shrimp lethality assay) of these extracts has also been assessed.

Determination of residues in the norepinephrine transporter that are critical for tricyclic antidepressant affinity

The norepinephrine (NET) and dopamine (DAT) transporters are highly homologous proteins, displaying many pharmacological similarities. Both transport dopamine with higher affinity than norepinephrine and are targets for the psychostimulants cocaine and amphetamine. However, they strikingly contrast in their affinities for tricyclic antidepressants (TCA). Previous studies, based on chimeric proteins between DAT and NET suggest that domains ranging from putative transmembrane domain (TMD) 5 to 8 are involved in the high affinity binding of TCA to NET. We substituted 24 amino acids within this region in the human NET with their counterparts in the human DAT, resulting in 22 different mutants. Mutations of residues located in extra- or intracytoplasmic loops have no effect on binding affinity of neither TCA nor cocaine. Three point mutations in TMD6 (F316C), -7 (V356S), and -8 (G400L) induced a loss of TCA binding affinity of 8-, 5-, and 4-fold, respectively, without affecting the affinity of cocaine. The triple mutation F316C/V356S/G400L produced a 40-fold shift in desipramine affinity. These three residues are strongly conserved in all TCA-sensitive transporters cloned in mammalian and nonmammalian species. A strong shift in TCA affinity (IC(50)) was also observed for double mutants F316C/D336T (35-fold) and S399P/G400L (80-fold for nortriptyline and 1000-fold for desipramine). Reverse mutations P401S/L402G in hDAT did not elicit any gain in TCA affinities, whereas C318F and S358V resulted in a 3- and 10-fold increase in affinity, respectively. Our results clearly indicate that two residues located in TMD6 and -7 of hNET may play an important role in TCA interaction and that a critical region in TMD8 is likely to be involved in the tertiary structure allowing the high affinity binding of TCA.

Tissue distribution and functional expression of the human voltage-gated sodium channel beta3 subunit

This study investigated the distribution of beta3 in human tissues and the functional effects of the human beta3 subunit on the gating properties of brain and skeletal muscle alpha subunits. Using RT-PCR of human cDNA panels, beta3 message was detected in brain, heart, kidney, lung, pancreas and skeletal muscle. Both alphaIIA and SkM1 expressed in Xenopus oocytes inactivated with a time course described by two exponential components representing fast and slow gating modes, while co-expression of human beta3 with alphaIIA or SkM1 significantly increased the proportion of channels operating by the fast gating mode. In the presence of beta3 a greater proportion of alphaIIA or SkM1 current was described by the fast time constant for both inactivation and recovery from inactivation. beta3 caused a hyperpolarizing shift in the voltage dependence of inactivation of alphaIIIA and reduced the slope factor. The voltage dependence of inactivation of SkM1 was described by a double Boltzmann equation. However, SkM1 co-expressed with beta3 was described by a single Boltzmann equation similar to one of the Boltzmann components for SkM1 expressed alone, with a small positive shift in V1/2 value and reduced slope factor. This is the first study demonstrating that beta3 is expressed in adult mammalian skeletal muscle and can functionally couple to the skeletal muscle alpha subunit, SkM1.

Hydrogen bonding in salicylsalicylic acid (salsalate) crystals

An X-ray crystallographic study of the drug salsalicylic acid (salsalate) has been performed. Crystal formation of the drug is influenced by both inter- and intra-molecular hydrogen bonding. In addition an OH group in salsalate can occupy alternate ortho positions resulting in two hydrogen bonding motifs within a single crystal.

Compressed xanthan and karaya gum matrices: hydration, erosion and drug release mechanisms

Directly compressed matrices were produced containing either xanthan gum or karaya gum as a release-controlling agent. These swellable hydrophilic natural gums were used to control the release of varying proportions of two model drugs, caffeine and diclofenac sodium, which have different solubilities in aqueous medium. Gum erosion, hydration and drug release studies were carried out using a dissolution apparatus (basket method) at two agitation speeds. Xanthan gum displayed a high degree of swelling due to water uptake and a small degree of erosion due to polymer relaxation. Neither agitation speed nor drug solubility had any significant effect on water uptake, but matrices with the lower proportion of gum produced a lesser degree of hydration. In contrast, karaya gum displayed a much lower hydration capacity and a higher rate of erosion, both markedly affected by agitation speed. Drug release from xanthan and karaya gum matrices depended on agitation speed, solubility and proportion of drug. Both xanthan and karaya gums produced near zero order drug release with the erosion mechanism playing a dominant role, especially in karaya gum matrices.

Absorption, disposition, and metabolism of rosiglitazone, a potent thiazolidinedione insulin sensitizer, in humans

Rosiglitazone is a potent peroxisome proliferator-activated receptor gamma agonist that decreases hyperglycemia by reducing insulin resistance in patients with type 2 diabetes mellitus. The disposition of (14)C-labeled rosiglitazone was determined after oral and i.v. dosing of rosiglitazone solution, and the disposition of nonradiolabeled rosiglitazone was determined after oral dosing of tablets in this open-label, three-part, semirandomized, crossover study. The absorption of rosiglitazone was rapid and essentially complete, with absolute bioavailability estimated to be approximately 99% after oral tablet dosing and approximately 95% after oral solution dosing, and clearance was primarily metabolic. The time to maximal concentration of radioactivity and the elimination half-life for two metabolites in plasma were significantly longer than for rosiglitazone itself (4-6 h versus 0. 5-1 h, and ca. 5 days versus 3-7 h). Radioactivity was excreted primarily via the urine ( approximately 65%) and was excreted similarly after oral and i.v. dosing. The major routes of metabolism were N-demethylation and hydroxylation with subsequent conjugation, of which neither was affected by the route of drug administration. The major metabolites, those of intermediate importance, and nearly all of the trace metabolites in humans have been identified previously in preclinical studies. Rosiglitazone was well tolerated in all formulations.

(p-Nitrobenzoato)triphenyltin at 298 K

The structure at 298 K described here, [Sn(C(6)H(5))(3)(C(7)H(4)NO(4))], completely confirms the results at 173 K obtained previously [Weng, Das & Robinson (1990), Malays. J. Sci. 12, 57]. In both structures, weak interaction between Sn and the carbonyl O atom of the benzoate group provides a distorted trigonal-pyramidal environment at the Sn atom derived from its pseudo-tetrahedral primary coordination in both molecules of the asymmetric unit.

beta 3: an additional auxiliary subunit of the voltage-sensitive sodium channel that modulates channel gating with distinct kinetics

The voltage-sensitive sodium channel confers electrical excitability on neurons, a fundamental property required for higher processes including cognition. The ion-conducting alpha-subunit of the channel is regulated by two known auxiliary subunits, beta1 and beta2. We have identified rat and human forms of an additional subunit, beta3. It is most closely related to beta1 and is the product of a separate gene localized to human chromosome 11q23.3. When expressed in Xenopus oocytes, beta3 inactivates sodium channel opening more slowly than beta1 does. Structural modeling has identified an amino acid residue in the putative alpha-subunit binding site of beta3 that may play a role in this difference. The expression of beta3 within the central nervous system differs significantly from beta1. Our results strongly suggest that beta3 performs a distinct neurophysiological function.

Correlating physiology with gene expression in striatal cholinergic neurones

The expression of 34 transmitter-related genes has been examined in the cholinergic neurones of rat striatal brain slices, with the aim of correlating gene expression with functional activity. The mRNAs encoding types I, II/IIA, and III alpha subunits of the voltage-sensitive sodium channels were detected, suggesting the presence of these three types of sodium channel. Similarly, mRNAs encoding all four alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-type glutamate receptor subunits and the NR1 and NR2A, 2B, and 2D subunits of the NMDA-type glutamate receptors were detected, suggesting that various combinations of these subunits mediate the cellular response to synaptically released glutamate. Other mRNAs detected included the NK1 and NK3 tachykinin receptors, all four known adenosine receptors, and the GABA-synthesising enzyme glutamate decarboxylase. Subpopulations of these cholinergic neurones have been identified on the basis of the expression of the NK3 tachykinin receptor in 5% and the trkC neurotrophin receptor in 12% of the cells investigated.

Studies of polymorphism in three compounds by single crystal X-ray diffraction

The role of single crystal diffraction in the quantitative determination of polymorphism is demonstrated by the examination of three compounds. Two polymorphs were found for each of the compounds bis(2-nitrophenyl) trisulphide (1), 2-amino-5-nitrobenzophenone (2) and bis(2-nitrophenyl) sulphide (3). Only in one polymorph of (1) does molecular symmetry correspond with crystallographic symmetry. In (2) the polymorphs arise in the same crystal class and in the same crystallographic space group whereas in (3) the two polymorphs exist in different crystal classes and hence in different space groups. Crystallographic space group transformation is also discussed.

Development and evaluation of a multiple-unit oral sustained release dosage form for S(+)-ibuprofen: preparation and release kinetics

Mini-matrix tablets containing S(+)-ibuprofen have been prepared by the wet granulation method. The hydrophilic matrix was formed with either xanthan gum, karaya gum or hydroxymethylcellulose (HPMC) together with a choice of additives from lactose, Encompress(R), Avicel(R) PH101, talc and Lubritab(R). Multiple unit dosage forms (MUDFs) were subsequently obtained by encapsulating the mini-matrix tablets into hard gelatin capsules. Preparation, in vitro release profiles and release kinetics are presented.

Evaluation of biodegradable rifampicin-bearing microsphere formulations using a stability-indicating high-performance liquid chromatographic assay

The validation of a rapid and selective stability-indicating high-performance liquid chromatographic procedure for the determination of rifampicin (RIF) and its decomposition products in aqueous solution is described. Direct injection and column switching HPLC procedures have been compared and, owing to the increased sensitivity and precision, the latter has been applied to the study of RIF stability in the presence of isoascorbic acid at pH 7.4. The time-dependent hydrolytic decomposition of RIF to 3-formyl rifamycin SV (RSV) was found to be biexponential. Log concentration versus time plots of RIF and RSV decomposition were found to be parallel, indicating a pseudo equilibrium decomposition process. This feature allowed corrections for the amounts lost to secondary reactions to be calculated when the assay was applied to the determination of release characteristics of RIF from biodegradable poly-d, l-lactide-co-glycolide microspheres.

First Report of Basil Leaf Spot Caused by Pseudomonas cichorii in Louisiana and Cultivar Screening Results

A leaf spot of basil, Ocimum basilicum L., was observed on container-grown and field plantings of cultivars Aussie Sweet and Sweet Basil. The disease was of minor importance under field conditions, but was of potential economic importance in seedling production. Gray to black, watersoaked, necrotic spots commonly developed at leaf margins. Large numbers of bacteria were released from cut lesions when viewed by light microscopy. Single colony bacterial isolates were established on nutrient dextrose agar (NDA) and yeast extract-dextrose-calcium carbonate agar (YDC). Pathogencity tests were performed by misting a water suspension containing 10⁴ bacterial cells per ml on healthy basil plants. Plants were held for 24 h in a dew chamber at 26°C and then moved to a greenhouse for observation. Typical leaf spots developed on inoculated plants in 2 days, but not on healthy control plants, and the bacterium was reisolated. The bacterium was characterized as a gram-negative, motile rod, negative for potato rot test, positive in tobacco hypersensitivity test, and oxidase positive. Isolates were identified as Pseudomonas cichorii according to the Biolog Microplate system (similarities ranged from 0.937 to 0.995). Screening tests were conducted by inoculating 15 basil cultivars, six replicates each, and rating them for disease severity based on a scale of 1 to 5 in which 1 = no disease and 5 = dead plants. Cultivars most resistant to bacterial leaf spot (ratings in parentheses are averages of two tests and those followed by the same letter are not significantly different according to Tukey's Studentized Range Test, P = 0.05) were Green Bouquet (2.0 a), Piccolo (2.2 a), Mrs. Burn's Lemon (2.2 a), Genovese (2.4 a), and Dark Opal (2.5 ab). Moderately susceptible cultivars were Bush Green (2.8 abc), Sweet Basil (2.8 abc), Large Green (2.9 abcd), Lemon (3.1 abcd), and Mexican Spice (3.6 bcd). The most susceptible cultivars were Lettuce Leaved (3.8 cd), Thai (3.8 cd), Napoletano (4.0 de), Green Ruffles (5.0 e), and Purple Ruffles (5.0 e). Bacterial leaf spot of basil caused by P. cichorii was first reported in the U.S. from Florida (1). Other bacterial diseases reported on basil include leaf blight from Egypt caused by P. syringae (2) and leaf necrosis from California caused by P. viridiflava (3). This is the first report on the occurrence of basil bacterial leaf spot in Louisiana and the first reported information on cultivar susceptibility. References: (1) S. M. Burgess et al. Proc. Fla. State Hortic. Soc. 99:249, 1986. (2) S. A. M. El-Sadek et al. Assiut J. Agric. Sci. 22:2, 1991. (3) E. L. Little et al. Plant Dis. 78:831, 1994.

Relationship between swelling, erosion and drug release in hydrophillic natural gum mini-matrix formulations

The swelling, erosion and solvent front penetration properties of mini-matrices containing xanthan (X), locust bean (LB) and karaya (K) gums were examined, analysed and related to the overall in vitro release kinetics of diclofenac sodium, used as a model drug. Mini-matrices were produced with drug:gum ratios of 1:1 as well as formulations of drug and X in combinations of 2:1, 2:3 and 1:2. The rank order of decreasing swelling index (SI) in both axial and radial dimensions was X?K?LB and each gum showed almost Fickian swelling behaviour. The solvent front penetration rates were consistent with the rates of swelling. However, the order of decreasing drug release and erosion rates was LB>X>K and all formulations demonstrated anomalous (non-Fickian) drug release kinetics. Therefore Fickian drug diffusion and polymer erosion were both occurring simultaneously. The dominant mechanism depended on the nature and content of the gum, as well as the stage in the dissolution time period. There was a loss of matrix integrity in formulations containing a high drug:gum ratio.

Improving the outcome of paediatric orthopaedic trauma: an audit of inpatient management in Southampton

The patterns, management and outcome of non-fatal orthopaedic injury in childhood was audited over a 1 year period in Southampton. A computer-based audit (1 September 1993 to 31 August 1994) was conducted of all children aged under 15 years who were admitted to the orthopaedic unit after accidental injury. Management was audited by studying the primary conservative and operative treatment methods employed. Treatment outcome was evaluated in terms of need for secondary operative treatment, salvage internal fixation, length of hospital stay and unplanned readmission. In all, 398 children, representing 50/10,000 of the local paediatric population, were admitted with a traumatic injury. There was a significant (P < 0.001, Kolmogorov-Smirnov) seasonal variation in admission rate. There were 87.3% admissions required for fractures, 8.5% after soft tissue injury and 2.2% after joint injury. The following areas were identified where management and outcome could be improved: 1 A 12.1% readmission rate (47/346) in children with fractures owing to a 16% incidence of loss of position after closed reduction of distal radial, forearm shaft and distal humeral fractures. 2 In all, 24% of internal fixation procedures were performed as 'salvage' after failure of conservative treatment, entailing either reoperation during the initial admission or a further unplanned readmission. 3 A prolonged inpatient stay for patients with femoral fractures owing to a wide variation in treatment method. The outcome of non-fatal orthopaedic injury can be improved through the selective use of primary internal fixation of distal radial and humeral fractures and the close adherence to a management algorithm in femoral fractures. There may be a role for more specialised supervision of primary treatment of these particular fractures.

Clinical characterization of Dicea a new cellulose membrane for haemodialysis

A prospective randomised clinical study comparing the functional performance and biocompatibility of a new cellulose diacetate variant (Dicea) in which the degree of hydroxyl group substitution differs, with cellulose diacetate and low flux polysulfone incorporated into commercially produced hollow fiber hemodialysers with a surface area 1.5-1.6 m2 has been undertaken. All dialysers studied demonstrated clinically acceptable performance in terms of their small molecular removal characteristics, with minor statistical but not clinical differences. Use of both cellulose diacetate membranes but not low flux polysulfone resulted in a reduction in plasma beta(2) microglobulin levels. The membranes were impermeable to albumin, but showed some permeability to low molecular weight proteins. The average protein recovery from the dialysis fluid was 3105 mg for Dicea, 2913 mg for cellulose diacetate and 2842 mg for low flux polysulfone. For Dicea the white cell count by 15 minutes had declined to 68% of pre treatment value, compared with 59% and 86% for cellulose diacetate and low flux polysulfone. The differences between Dicea and cellulose diacetate were not significant, but both cellulose based membranes differed from low flux polysulfone (p = 0.0015). There was a strong evidence of differences between the membranes in respect of C5a and C5b-9 generation (p = 0.0001) but not for C3a (p = 0.16) furthermore the levels of C5b-9 generated during dialysis also showed a significant positive correlation compared to C5a for all membranes. (Pearson's correlation coefficient = 0.856, p = 0.0001). It is concluded that the two cellulose diacetate membranes are not identical, with the differences observed being a consequence of the degree of acetyl substitution, resulting in alteration of membrane structure and the method of sterilization. The clinical significance of these differences are difficult to characterize but the modification of the cellulose structure appears to be a promising method to improve the biocompatibility of cellulose membranes. The improved biocompatibility offered by this method still falls short of that achieved with low flux synthetic membranes such as Fresenius Polysulfone.

A comparison of three brands of polysulfone membranes

A prospective clinical crossover study comparing the functional performance and biocompatibility of three brands of polysulfone membranes (Fresenius Polysultone (Fresenius Ag, Bad Homburg, Germany), Polyphen (Minntech Corp., Minneapolis, MN), and Biosulfane (WR Grace Inc., Danvers, MA)) incorporated in ethylene oxide-sterilized dialyzers of comparable surface area (1.3 to 1.35 m2) was undertaken. The clearance of small molecules by each membrane was comparable. Plasma levels of beta 2 microglobulin fell to 49.9% of pretreatment values by 210 min when using the Fresenius Polysulfone membrane, 60.2% with the Polyphen membrane, and 63.1% with the Biosulfane membrane. The reduction achieved by the Fresenius Polysulfone membrane was superior (P = 0.003). The plasma reductions were associated with the recovery of 195 mg beta 2 microglobulin from the dialysate for the Fresenius Polysulfone membrane and 158 mg for the Polyphen membrane, but no beta 2 microglobulin was recovered from the dialysate with the Biosulfane membrane. The dialysate collected with the Fresenius Polysulfone membrane also contained a mean of 6853 mg of total protein, compared with 5490 mg with the Polyphen membrane and 8422 mg with the Biosulfane (P = 0.04) membrane. The neutropenia was slight and independent of membrane brand, as were the changes in C3a des arg and SC5b-9 complement components. The reduction in platelet counts was higher for the Biosulfane membrane than for the other brands (P = 0.003). This study indicates that whereas the polymer base of the membrane is the same, its production and subsequent handling during dialyzer production induce changes that attain statistical significance, most notably in the way that the membrane removes beta 2 microglobulin and interacts with proteins. The differences observed are a consequence of the different alloying polymers used during manufacture and, consequently, the membranes cannot be considered equivalent.

Application of a standard method to characterize clearance blood flow relationships in hemodialysis

The effectiveness of solute removal of a hemodialyzer may be judged by the ability of the device to remove solutes over the clinical range of blood flow rates. The expression of solute removal characteristics of hemodialyzers at standard or specific blood flow rates is important for clinical use and comparison. The solute removal at a specific blood flow rate is derived mathematically, usually by the fitting of a curve to the blood flow solute removal characteristics established experimentally over a range of blood flow rates. The commonly used methods of obtaining such a relationship are discussed and a new method of curve fitting is described. This method is derived from the mathematical theory defining the overall dialyzer mass transport relationship which governs the clearance blood flow relationship in any dialyzer. The derived relationship between the blood flow rate and the clearance has been validated using data generated for a commercially produced hemodialyzer.