The empty pelvis syndrome: a core data set from the PelvEx collaborative

BACKGROUND

Empty pelvis syndrome (EPS) is a significant source of morbidity following pelvic exenteration (PE), but is undefined. EPS outcome reporting and descriptors of radicality of PE are inconsistent; therefore, the best approaches for prevention are unknown. To facilitate future research into EPS, the aim of this study is to define a measurable core outcome set, core descriptor set and written definition for EPS. Consensus on strategies to mitigate EPS was also explored.

METHOD

Three-stage consensus methodology was used: longlisting with systematic review, healthcare professional event, patient engagement, and Delphi-piloting; shortlisting with two rounds of modified Delphi; and a confirmatory stage using a modified nominal group technique. This included a selection of measurement instruments, and iterative generation of a written EPS definition.

RESULTS

One hundred and three and 119 participants took part in the modified Delphi and consensus meetings, respectively. This encompassed international patient and healthcare professional representation with multidisciplinary input. Seventy statements were longlisted, seven core outcomes (bowel obstruction, enteroperineal fistula, chronic perineal sinus, infected pelvic collection, bowel obstruction, morbidity from reconstruction, re-intervention, and quality of life), and four core descriptors (magnitude of surgery, radiotherapy-induced damage, methods of reconstruction, and changes in volume of pelvic dead space) reached consensus-where applicable, measurement of these outcomes and descriptors was defined. A written definition for EPS was agreed.

CONCLUSIONS

EPS is an area of unmet research and clinical need. This study provides an agreed definition and core data set for EPS to facilitate further research.

An evaluation of low back pain among farmers in Ireland

BACKGROUND

Low back pain (LBP) is the most commonly reported musculoskeletal disorder among farmers. There is limited research regarding LBP among farmers in Ireland.

AIMS

To explore attributed causes of LBP, investigate the relationship between LBP and personal and work-related factors and measure the impact of LBP.

METHODS

A questionnaire survey of Irish farmers was conducted on farmers from each of the main farm enterprise systems in Ireland. Data were analysed using chi-square tests, t-tests, Mann-Whitney tests and logistic regression models.

RESULTS

There were 600 farmers included in the survey with 100 from each of the six main farm systems. Lifting/pulling/pushing was identified as the most commonly attributed cause of LBP. In the multiple regression analysis the variables found to be associated with LBP included farm size and self-rated health. The odds ratios (OR) of LBP were greater among operators of medium and large farms [(OR = 1.52; 95% confidence interval (CI): 1.04-2.22 and OR = 1.86; 95% CI: 1.16-3.98, respectively] compared with smaller farms (P < 0.05). Those who perceived health as 'good' (OR = 1.63; 95% CI: 1.14-2.33) by comparison with a rating of 'very good' had greater odds of LBP (P < 0.01). Some farmers changed work habits, sought help and needed time off work due to LBP.

CONCLUSIONS

Lifting was identified as the main attributed cause for LBP. LBP leads to work disability that necessitated farmers changing work habits, getting help and needing time off work. In order to reduce LBP-related disability among farmers in the future, work practices involving lifting need to be further investigated.

The SLC16 monocaboxylate transporter family

1. The monocarboxylate transporter (MCT, SLC16) family comprises 14 members, of which to date only MCT1-4 have been shown to carry monocarboxylates, transporting important metabolic compounds such as lactate, pyruvate and ketone bodies in a proton-coupled manner. The transport of such compounds is fundamental for metabolism, and the tissue locations, properties and regulation of these isoforms is discussed. 2. Of the other members of the MCT family, MCT8 (a thyroid hormone transporter) and TAT1 (an aromatic amino acid transporter) have been characterized more recently, and their physiological roles are reviewed herein. The endogenous substrates and functions of the remaining members of the MCT family await elucidation. 3. The MCT proteins have the typical twelve transmembrane-spanning domain (TMD) topology of membrane transporter proteins, and their structure-function relationship is discussed, especially in relation to the future impact of the single nucleotide polymorphism (SNP) databases and, given their ability to transport pharmacologically relevant compounds, the potential impact for pharmacogenomics.

Extracellular and subcellular regulation of the PI3K/Akt cassette: new mechanisms for controlling insulin and growth factor signalling

The PI3K (phosphoinositide 3-kinase)/Akt (also called protein kinase B) signalling cassette plays a central role in the response to growth factors, particularly insulin-like molecules, and its misregulation is a characteristic feature of diabetes and many forms of human cancer. Recent molecular genetic studies initiated in the fruitfly, Drosophila melanogaster, have highlighted two new cell-type-specific mechanisms regulating PI3K/Akt signalling and its downstream effects. First, the cellular response to this cassette is modulated by several classes of cell-surface transporters and sensors, suggesting an important role for extracellular nutrients in insulin-sensitivity. Secondly, various cell types show a markedly different subcellular distribution of the activated kinase Akt, influencing the cellular functions of this molecule. These findings reveal new mechanisms by which processes such as growth, lipogenesis and insulin resistance can be differentially regulated and may suggest novel strategies for treating insulin-linked diseases.

Molecular Modeling of PepT1 — Towards a Structure

The proton-coupled uptake of di- and tri-peptides is the major route of dietary nitrogen absorption in the intestine and of reabsorption of filtered protein in the kidney. In addition, the transporters involved, PepT1 (SLC15a1) and PepT2 (SLC15a2), are responsible for the uptake and tissue distribution of a wide range of pharmaceutically important compounds, including beta-lactam antibiotics, angiotensin-converting enzyme inhibitors, anti-cancer and anti-viral drugs. PepT1 and PepT2 are large proteins, with over 700 amino acids, and to date there are no reports of their crystal structures, nor of those of related proteins from lower organisms. Therefore there is virtually no information about the protein 3-D structure, although computer-based approaches have been used to both model the transmembrane domain (TM) layout and to produce a substrate binding template. These models will be discussed, and a new one proposed from homology modeling rabbit PepT1 to the recently crystallized bacterial transporters LacY and GlpT. Understanding the mechanism by which PepT1 and PepT2 bind and transport their substrates is of great interest to researchers, both in academia and in the pharmaceutical industries.

Characterisation of human monocarboxylate transporter 4 substantiates its role in lactic acid efflux from skeletal muscle

Monocarboxylate transporter (MCT) 4 is the major monocarboxylate transporter isoform present in white skeletal muscle and is responsible for the efflux of lactic acid produced by glycolysis. Here we report the characterisation of MCT4 expressed in Xenopus oocytes. The protein was correctly targeted to the plasma membrane and rates of substrate transport were determined from the rate of intracellular acidification monitored with the pH-sensitive dye 2', 7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). In order to validate the technique, the kinetics of monocarboxylate transport were measured in oocytes expressing MCT1. Km values determined for L-lactate, D-lactate and pyruvate of 4.4, > 60 and 2.1 mM, respectively, were similar to those determined previously in tumour cells. Comparison of the time course of [14C]lactate accumulation with the rate of intracellular acidification monitored with BCECF suggests that the latter reflects pH changes close to the plasma membrane associated with transport, whilst the former may include diffusion-limited movement of lactate into the bulk cytosol. Km values of MCT4 for these substrates were found to be 28, 519 and 153 mM, respectively, and for a range of other monocarboxylates values were at least an order of magnitude higher than for MCT1. Vmax values appeared to be similar for all substrates. K0.5 values of MCT4 (determined at 30 mM L-lactate) for inhibition by alpha-cyano-4-hydroxycinnamate (991 microM), phloretin (41 microM), 5-nitro-2-(3-phenylpropylamino)benzoate (240 microM), p-chloromercuribenzene sulphonate (21 microM) and 3-isobutyl-1-methylxanthine (970 microM, partial inhibition) were also substantially higher than for MCT1. No inhibition of MCT4 by 2 mM 4,4'-diisothiocyanostilbene-2,2'-disulphonate was observed. The properties of MCT4 are consistent with published data on giant sarcolemmal vesicles in which MCT4 is the dominant MCT isoform, and are appropriate for the proposed role of MCT4 in mediating the efflux from the cell of glycolytically derived lactic acid but not pyruvate.

Characterization of benzodiazepine receptors in the cerebellum

1. The goals of the work reported here were to further characterize benzodiazepine/GABA(A) (BDZR) receptor heterogeneity in the cerebellum and to measure the affinities and selectivities of structurally diverse benzodiazepines at each site identified. 2. Five chemical families were included in these studies. These were 1,4-benzodiazepines (flunitrazepam), imidazobenzodiazepines (RO15-1788 and RO15-4513 and RO16-6028), beta-carbolines (Abecarnil) and pyrazoloquinolines (CGS 8216, CGS 9895 and CGS 9896). 3. Saturation and competition binding assays were combined with powerful data analysis software developed in our laboratory. Among the capabilities of this software is the identification of multiple binding sites for a cold ligand using a non-selective labeled ligand that binds with equal, but high, affinity to all the binding sites 4. Saturation binding assays using either [3H]-RO15-1788 or [3H]-RO15-4513 revealed only one apparent binding site, with a higher affinity for RO15-4513 than for RO15-1788. However, using [3H]-RO15-4513 for the competition binding studies in the cerebellum, together with our data analysis software, led to the identification of two distinct binding sites with equal densities for the diverse benzodiazepines studied. 5. In rat cerebellum one of the sites identified corresponds to GABA(A) receptors exhibiting alpha1 subunit pharmacology and the other to GABA(A) receptors exhibiting alpha6 subunit pharmacology. In general, the diverse families of BDZR ligands studied had much lower affinities for the alpha6 containing receptors.

Unraveling the identity of benzodiazepine binding sites in rat hipppocampus and olfactory bulb

The goals of the work reported here were (i) to identify distinct GABA(A)/benzodiazepine receptors in the rat hippocampus and olfactory bulb using receptor binding assays, and (ii) to determine the affinities and selectivities of benzodiazepine receptor ligands from structurally diverse chemical families at each site identified. These studies were aided by the use of software AFFINITY ANALYSIS SYSTEM, developed in our laboratory for analysis of receptor binding data that allows the determination of receptor heterogeneity using non-selective radioligands. Saturation binding assays using [3H]RO15-4513 (ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazo[1, 5-a]-[1,4]benzodiazepine-3-carboxylate) revealed two binding sites in each of these two tissues. The higher affinity site corresponds to alpha(5) subunit-containing GABA(A) receptor and the lower affinity site to a combination of alpha(1), alpha(2), and alpha(3) subunit-containing receptors. These results should be useful in the challenging task of identifying the various functional GABA(A) receptors in the central nervous system, and in providing a link between receptor affinities and in vivo activities of the GABA(A)/benzodiazepine receptor ligands studied.

Modified amino acids and peptides as substrates for the intestinal peptide transporter PepT1

The binding affinities of a number of amino-acid and peptide derivatives by the mammalian intestinal peptide transporter PepT1 were investigated, using the Xenopus laevis expression system. A series of blocked amino acids, namely N-acetyl-Phe (Ac-Phe), phe-amide (Phe-NH2), N-acetyl-Phe-amide (Ac-Phe-NH2) and the parent compound Phe, was compared for efficacy in inhibiting the uptake of the peptide [3H]-D-Phe-L-Gln. In an equivalent set of experiments, the blocked peptides Ac-Phe-Tyr, Phe-Tyr-NH2 and Ac-Phe-Tyr-NH2 were compared with the parent compound Phe-Tyr. Comparing amino acids and derivatives, only Ac-Phe was an effective inhibitor of peptide uptake (Ki = 1.81+/- 0.37 mM). Ac-Phe-NH2 had a very weak interaction with PepT1 (Ki = 16.8+/-5.64 mM); neither Phe nor Phe-NH2 interacted with PepT1 with measurable affinity. With the dipeptide and derivatives, unsurprisingly the highest affinity interaction was with Phe-Tyr (Ki = 0.10+/-0.04 mM). The blocked C-terminal peptide Phe-Tyr-NH2 also interacted with PepT1 with a relatively high affinity (Ki = 0.94+/-0.38 mM). Both Ac-Phe-Tyr and Ac-Phe-Tyr-NH2 interacted weakly with PepT1 (Ki = 8.41+/-0.11 and 9.97+/-4.01 mM, respectively). The results suggest that the N-terminus is the primary binding site for both dipeptides and tripeptides. Additional experiments with four stereoisomers of Ala-Ala-Ala support this conclusion, and lead us to propose that a histidine residue is involved in binding the C-terminus of dipeptides. In addition, a substrate binding model for PepT1 is proposed.

Structure and function of eukaryotic peptide transporters

The cotransport of protons and peptides is now recognised as a major route by which dietary nitrogen is absorbed from the intestine, and filtered protein reabsorbed in the kidney. Recently, molecular biology has had a very substantial impact on the study of peptide transport, and here we review the molecular and functional information available within the framework of physiology. To this end we consider not only the mammalian peptide transporters and their tissue distribution and regulation but also those from other species (including Caenorhabditis elegans) which make up the proton-dependent oligopeptide transport superfamily. In addition, understanding the binding requirements for transported substrates may allow future design and targeted tissue delivery of peptide and peptidomimetic drugs. Finally, we aim to highlight some of the less well understood areas of peptide transport, in the hope that it will stimulate further research into this challenging yet exciting topic.

Distinct transcriptional and functional properties of the R transactivator gene orf50 of the transforming herpesvirus saimiri strain C488

The transformation-associated region of herpesvirus saimiri strains is variable, whereas other parts of the virus genome are highly conserved. However, we observed considerable interstrain sequence divergence of the early viral regulatory orf50 gene, which encodes the R transactivator, a homolog of Epstein-Barr virus BRLF1. The orf50 gene of strain C488 was transcribed at low abundance during lytic infection, whereas antisense transcripts were simultaneously expressed at high levels. A spliced variant, orf50a, was detectable by RT-PCR and RNase protection assays in stimulated C488-transformed, nonpermissive human T cells. In contrast to strain A11, the short, unspliced orf50b form of C488 displayed complete transactivation capability on the orf6 and orf57 promoters. In summary, there are unexpected structural and functional differences between the orf50 genes of herpesvirus saimiri strains, which differ in their capability to transform human T lymphocytes.

How to Make Drugs Orally Active: A Substrate Template for Peptide Transporter PepT1

By building key structural features into hydrophilic drugs, they can be recognized by the PepT1 transporter system of the small intestine and rendered orally active. The model shown provides, for the first time, a 3D template for all known substrates of PepT1.

Fulminant desquamative interstitial pneumonitis

A previously well, 48-year-old female presented with a short history of respiratory distress and fever for which no cause could be found. Open lung biopsy was not contributory. She died within nine days of presentation of hypoxia and multi-organ failure. Post mortem examination revealed the pattern of desquamative interstitial pneumonitis.

4-aminomethylbenzoic acid is a non-translocated competitive inhibitor of the epithelial peptide transporter PepT1

1. 4-Aminomethylbenzoic acid, a molecule which mimics the special configuration of a dipeptide, competitively inhibits peptide influx in both Xenopus Laevis oocytes expressing rabbit PepT1 and through PepT1 in rat renal brush border membrane vesicles. 2. This molecule is not translocated through PepT1 as measured both by direct HPLC analysis in PepT1-exp ressing oocytes and indirectly by its failure to trans-stimulate labelle d peptide efflux through PepT1 in oocytes and in renal membrane vessicle s. 3. However 4-aminiomethylbenzoic acid does reverse trans-stimulation through expressed PepT1 of labelled peptid efflux induced by unlabelled peptide. Quantitatively this reversal is compatible with 4-aminomethyl benzoic acid competitively binding to the external surface of PepT1. 4. 4-Aminomethylbenzoic acid (the first molecule discovered to be a non-translocated competitive inhibitor of proton-coupled oligopeptide transport) and its derivatives may thus be particularly useful as experimental tools.

Peptide mimics as substrates for the intestinal peptide transporter

4-Aminophenylacetic acid (4-APAA), a peptide mimic lacking a peptide bond, has been shown to interact with a proton-coupled oligopeptide transporter using a number of different experimental approaches. In addition to inhibiting transport of labeled peptides, these studies show that 4-APAA is itself translocated. 4-APAA transport across the rat intact intestine was stimulated 18-fold by luminal acidification (to pH 6.8) as determined by high performance liquid chromatography (HPLC); in enterocytes isolated from mouse small intestine the intracellular pH was reduced on application of 4-APAA, as shown fluorimetrically with the pH indicator carboxy-SNARF; 4-APAA trans-stimulated radiolabeled peptide transport in brush-border membrane vesicles isolated from rat renal cortex; and in Xenopus oocytes expressing PepT1, 4-APAA produced trans-stimulation of radiolabeled peptide efflux, and as determined by HPLC, was a substrate for translocation by this transporter. These results with 4-APAA show for the first time that the presence of a peptide bond is not a requirement for rapid translocation through the proton-linked oligopeptide transporter (PepT1). Further investigation will be needed to determine the minimal structural requirements for a molecule to be a substrate for this transporter.

Both the H13 gene product and 4F2 antigen are involved in the induction of system y+ cationic amino-acid transport following activation of human peripheral blood mononuclear cells (PBM)

Prior transfection with antisense oligonucleotides to the H13 and 4F2 hc genes, singly or in combination, was found to inhibit phytohaemagglutinin-induced activation of cationic amino-acid transport system y+ in human peripheral blood mononuclear cells (mostly circulating lymphocytes). These effects on system y+ function or expression mean that 4F2 hc cannot only be the molecular basis of system y+L (Fei, Y.-J., Prasad, P.D., Leibach, F.H. and Ganapathy, V. (1995) Biochemistry 34, 8744-8751).

Dipeptide transport in brush-border membrane vesicles (BBMV) prepared from human full-term placentae

The uptakes of the tritiated, hydrolysis-resistant cationic (d-Phe-L-Lys), neutral (D-Phe-L-Ala) and anionic (D-Phe-L-Glu) peptides into human full-term placental brush-border membrane vesicles (BBMV) were time-dependent and into an osmotically-active space. Uptakes of D-Phe-L-Lys and D-Phe-L-Glu were temperature-dependent. Uptake of D-Phe-L-Lys was electroneutral (either cation exchange or anion co-transport), whereas D-Phe-L-Ala and D-Phe-L-Glu were both stimulated by an increasingly inside-positive membrane potential (explained by either cation exchange or anion co-transport, or translocation alone, respectively). Uptake of D-Phe-L-Ala was stimulated (approximately 50 per cent) by an inwardly-directed proton gradient (pHin = 7.4, pHout = 5.5), whereas D-Phe-L-Glu was unaffected, and D-Phe-L-Lys uptake was inhibited (approximately 50 per cent) but was unaffected by the organic cation-exchange inhibitors 1,1-diethyl-2,2-cyanine (decynium22) and 5-(N-methyl-N-isobutyl)amiloride (MIBA). Over the concentration range studies, the peptides did not self-inhibit, and the only cross-inhibition was by D-Phe-L-Glu on D-Phe-L-Lys uptake (estimated K(I) 24.2 +/- 1.36 mM), suggesting very low affinity transporter(s). Under conditions favouring its transport by PepT1, D-Phe-L-Glu uptake was unaffected by diethylpyrocarbonate (DEPC); neither D-Phe-L-Ala nor D-Phe-L-Lys was inhibited by DEPC under maximally proton-stimulated conditions of uptake. We conclude that Pep-T-like transporters are not responsible for peptide uptake into human placental BBMV; while the molecular identity of the transporter(s) involved remains unclear, we hypothesize that they could be similar to the as yet unidentified epithelial basolateral peptide transporter(s).

Dipeptide transport characteristics of the apical membrane of rat lung type II pneumocytes

The transport of a hydrolysis-resistant dipeptide, D-phenylalanyl-L-alanine (D-Phe-L-Ala), has been studied by high-performance liquid chromatography in rat lung epithelial cells and apical membrane vesicles. Time-dependent uptake of D-Phe-L-Ala into isolated type II pneumocytes was shown. Uptake was saturable, and Michaelis-Menten kinetics were fitted to the data and gave an apparent Michaelis constant (Km) of 3.4 mM and a maximum velocity (Vmax) of 7.0 nmol.mg protein-1.min-1. However, known peptide transport inhibitors unexpectedly increased intracellular D-Phe-L-Ala concentration when initial rates of peptide uptake were studied. Apical (brush-border) membrane vesicles prepared from rat lung also showed time- and concentration-dependent influx of D-Phe-L-Ala (apparent Km 2.0 mM, Vmax 0.53 nmol.mg protein-1.min-1). Influx of this neutral dipeptide into the vesicles was shown to be both electrogenic and stimulated by an inwardly directed proton gradient. Influx was inhibitable by mercuric chloride and by the amino acid residue modifying compounds N-acetylimidazole and diethylpyrocarbonate. These findings strongly suggest the presence of a proton-coupled peptide transport protein in the apical surface of the type II cell. This transporter may play a role in lung homeostasis.

Patient selection criteria for home i.v. therapies: from A to Z

Home intravenous therapy is a fast-growing industry, but it may not be for everyone: several medical and safety criteria must be met to ensure effective patient care. Home care agencies should examine each patient situation closely before deciding to implement a home i.v. program.

Tripeptide transport in rat lung

Transport of L-alanyl-D-phenylalanyl-L-alanine was investigated with an in situ vascular perfusion preparation of rat lung and brush border membrane vesicles prepared from type II pneumocytes. In the perfused lung 1 mM tripeptide was transported intact from the alveolar lumen to the vascular perfusate at a mean rate of 25.1 +/- 1.29 (3) nmol/min per g dry weight. D-Phenylalanine also appeared in the vascular perfusate at a rate of 21.9 +/- 1.74 (3) nmol/min per g dry weight indicating that 47% of the absorbed tripeptide was split during passage across the epithelial layer. No dipeptide could be detected in the vascular effluent during perfusions with tripeptide. Rapid L-alanyl-D-phenylalanyl-L-alanine uptake occurred with fresh apical membrane vesicles prepared from type II pneumocytes and this was abolished by treatment with 0.1% triton. The related tripeptide, D-alanyl-L-phenylalanyl-D-alanine, was taken up significantly more slowly by the vesicles. D-phenylalanyl-L-alanine and D-phenylalanyl-D-alanine, were also studied with the vascularly perfused preparation; the mixed dipeptide appeared in the vascular perfusate significantly faster than L-alanyl-D-phenylalanyl-L-alanine whereas D-phenylalanyl-D-alanine appeared more slowly and was not hydrolysed.

Abnormal erythrocyte choline transport in patients with chronic renal failure

1. Erythrocyte choline transport has been studied in nine patients on maintenance haemodialysis for chronic renal failure, six patients on continuous ambulatory peritoneal dialysis, 31 patients with renal transplants and in nine normal control subjects. 2. The mean maximum rate of choline influx (Vmax., measured at an extracellular choline concentration of 250 mumol/l) was 66.7 (SD 14.1) mumol h-1 l-1 cells in patients on haemodialysis, 87.8 (SD 18.5) mumol h-1 l-1 cells in patients on continuous ambulatory peritoneal dialysis and 30.5 (SD 4.9) mumol h-1 l-1 cells in control subjects. The increase in choline flux in patients on haemodialysis and patients on continuous ambulatory peritoneal dialysis compared with control subjects was highly significant (P less than 0.001). 3. Renal transplant patients showed variable values for the Vmax. of choline influx (range 17.7-71.7 mumol h-1 l-1 cells). The values showed a significant negative correlation with creatinine clearance and this correlation correctly extrapolated to the maximum choline flux in normal subjects and in patients on dialysis. 4. The kinetics of choline transport have been studied in erythrocytes of patients on haemodialysis and control subjects in 'zero-trans' conditions after depletion of intracellular choline. The mean Vmax. in these conditions was 38.4 (SD 4.6) mumol h-1 l-1 cells in patients on haemodialysis compared with 14.2 (SD 3.7) mumol h-1 l-1 cells in control subjects. The mean Km under 'zero-trans' conditions was 19.4 (SD 2.4) mumol/l in patients on haemodialysis and 7.4 (SD 1.4) mumol/l in control subjects. These differences were significant (P less than 0.001).

Uridine transport in human erythrocytes: data from normal subjects and from patients with renal failure

Erythrocyte uridine transport has been studied in eight normal individuals and eight patients on haemodialysis for chronic renal failure. The initial rate of zero-trans uridine influx at 37 degrees C has been measured as a function of extracellular uridine concentration using [14C]-labelled uridine. The results are consistent with Michaelis-Menten kinetics. In normal humans the mean Vmax for uridine influx was 32.8 +/- 6.4 mumol (1 cells)-1 s-1 (mean +/- S.D.) and the mean Km was 190 +/- 12.3 microM. The measurements made in renal failure patients were not significantly different (mean Vmax 30.1 +/- 7.1 mumol (1 cells)-1 s-1, mean Km, 185 +/- 13.2 microM). These results are discussed with reference to the reported data on uridine transport in human erythrocytes at temperatures between 4 and 35 degrees C; it is suggested that zero-trans uridine influx shows a decrease in temperature dependence above 25 degrees C. The Vmax for zero-trans uridine influx at 37 degrees C in normal erythrocytes represents a turnover number for the nucleoside transporter of 180 uridine molecules per second.

Doubly Labeled Water Validation in the Marsupial Petauroides-Volans

Amounts of carbon dioxide (CO2) produced by caged greater gliders were measured simultaneously by means of potassium hydroxide absorption, and by the low-level, doubly labelled water method, which incorporated a gas isotope ratio mass spectrometer for determining the low oxygen isotope enrichments. The two methods yielded significantly different values, but doubly labelled water underestimated CO2 production by only 8.3% on average, and this error is in the range of mean errors found in previous validation studies where no significant differences existed. In addition, we tested procedures designed to reduce the costs of using the doubly labelled water method, by streamlining field and laboratory procedures for sample handling and processing.

Equine leukocyte antigens: relationships with sarcoid tumors and laminitis in two pure breeds

Frequencies of equine leukocyte antigen distribution were determined by complement-mediated cytotoxicity testing among populations of Thoroughbred and Standardbred horses, including animals affected with equine sarcoid and laminitis. A highly significant association is described between the presence or history of sarcoid lesions in Thoroughbreds and the expression of the major histocompatibility complex (MHC)-encoded antigens, W3 and B1. No association was found between antigenic expression frequencies and laminitis in either breed. These findings suggest that a strong relationship exists between the equine MHC and a predisposition to sarcoid.

Monoclonal antibodies to herpes simplex virus thymidine kinase

Purified herpes simplex virus thymidine kinase has been used to immunize mice for the production of monoclonal antibodies to the enzyme. Monoclonal antibodies were successfully produced against both herpes simplex virus type 1 and type 2 enzymes. These antibodies should prove useful for detecting the enzyme under a variety of experimental conditions. We also demonstrate that the antibodies can provide an alternative method for obtaining large amounts of purified thymidine kinase.