Expression, purification and characterisation of the recombinant possum lipocalin vulpeculin

BACKGROUND

Lipocalins are a large family of proteins, which possess a highly conserved eight-stranded antiparallel beta-barrel structure as distinctive trait. This family includes Major Urinary Proteins (MUPs) from rats and mouse, studied for their role in urinary protein-mediated chemosignalling. Vulpeculin has been identified as the most abundant protein in the urine of the common brushtail possum, Trichosurus vulpecula. On the basis of high similarity with other MUPS, we hypothesised that vulpeculin might have a role in possum chemosignalling and investigated its stability and binding ability.

METHODS

We expressed and purified vulpeculin using an E.coli-based system and confirmed correct folding by circular dichroism (CD) spectroscopy. Thermal stability was studied by CD and binding properties were investigated using two optical probes N-phenyl-naphthylamine (NPN) and 8-anilino-1-naphthalene sulphonic acid (ANS).

RESULTS

CD revealed a secondary structure typical of a predominantly β-sheet protein, consistent with the beta barrel structure of the lipocalin family. Vulpeculin showed a high level of thermostability, as assessed by CD, exhibiting a small shift in the secondary structure even at 95 °C. Binding assays indicated that vulpeculin cannot accommodate the NPN ligand but can bind ANS.

CONCLUSION

The urinary secretion, high degree of sequence similarity with other lipocalins, its beta sheet structure assessed by CD and potential to bind hydrophobic ligands in the hydrophobic cavity or an external hydrophobic pocket, suggest vulpeculin may be involved in possum chemosignalling.

GENERAL SIGNIFICANCE

This work represents a first step towards the further investigation of the newly discovered lipocalin and its role in possum chemosignalling.

Selection and characterization of DNA aptamers for the rat major urinary protein 13 (MUP13) as selective biorecognition elements for sensitive detection of rat pests

Among invasive mammalian predators, rats represent a major threat, endangering ecosystem functioning worldwide. After rat-control operations, detecting their continued presence or reinvasion requires more sensitive and lower cost detection technologies. Here, we develop a new sensing paradigm by using a specific rat urine biomarker (MUP13) to unambiguously signal the presence of rats. As the first step towards a new remote surveillance technology, aptamers were selected to MUP13 using the Flu-Mag SELEX method. Six aptamer candidates were initially screened by dot blot and two of them (Apt-2.5 and Apt-1.4) exhibited high affinity and specificity. Both aptamers were further characterized by bead-based assay to confirm affinity and selectivity. The lead aptamer candidates were then applied to fluorescence anisotropy (FA) and surface plasmon resonance (SPR)-based biosensor platforms, showing dissociation constants in the nanomolar range and high specificity towards their target. The SPR biosensor had limits of detection of 13.8 and 7.5 nM for Apt-2.5 and Apt-1.4, respectively, which are more than three orders of magnitude lower than the physiological concentrations found in rat urine. Selectivity of the aptamers, when comparing with other major urinary proteins, was excellent, indicating strong efficacy in specific detection of rats. In order to validate the aptamer Apt-2.5 for use with real world samples a FA-based assay was performed on a rat urine sample. The assay showed that the aptamer could detect recombinant MUP13 spiked in filtered urine and the natural MUP13 in unfiltered urine, as a first step into translation to real world application. These are the first known assays to detect and quantify a MUP biomarker of rats.

Do rural primary health care nurses feel equipped for palliative care?

Community primary health care nurses in rural and remote settings are required to provide palliative care as part of their generalist role. They have limited access to specialist medical and nursing support and sometimes there are no resident GPs. A study consisting of a mailed survey and follow-up interviews was conducted to explore the experiences of these nurses and to determine how personally and professionally equipped they felt for palliative care service provision. Most participants were registered nurses experienced in nursing and in rural and remote settings, who juggled multiple generalist work roles. They had only occasional palliative care patients, and more than half had provided palliative care for a friend or family member. Some nurses found palliative care rewarding, others preferred not to have to do it. However, even those who did not enjoy working with palliative care patients often went beyond the 'call of duty' to support a home death if that was what the patient wanted. Three-quarters had attended palliative care education in the last 2 years but 88% wanted more education. Barriers to education included competing work roles, work load, geographical isolation and lack of backfill. Support from managers and peers was considered important, as was accessing timely and relevant clinical support.

Genotypic variation in the sulfur assimilation and metabolism of onion (Allium cepa L.) I. Plant composition and transcript accumulation

Organosulfur compounds are major sinks for assimilated sulfate in onion (Allium cepa L.) and accumulation varies widely due to plant genotype and sulfur nutrition. In order to better characterise sulfur metabolism phenotypes and identify potential control points we compared plant composition and transcript accumulation of the primary sulfur assimilation pathway in the high pungency genotype 'W202A' and the low pungency genotype 'Texas Grano 438' grown hydroponically under S deficient (S-) and S-sufficient (S+) conditions. Accumulation of total S and alk(en)yl cysteine sulfoxide flavour precursors was significantly higher under S+ conditions and in 'W202A' in agreement with previous studies. Leaf sulfate and cysteine levels were significantly higher in 'W202A' and under S+. Glutathione levels were reduced by S- treatment but were not affected by genotype, suggesting that thiol pool sizes are regulated differently in mild and pungent onions. The only significant treatment effect observed on transcript accumulation in leaves was an elevated accumulation of O-acetyl serine thiol-lyase under S-. By contrast, transcript accumulation of all genes in roots was influenced by one or more treatments. APS reductase transcript level was not affected by genotype but was strongly increased by S-. Significant genotype×S treatment effects were observed in a root high affinity-sulfur transporter and ferredoxin-sulfite reductase. ATP sulfurylase transcript levels were significantly higher under S+ and in 'W202A'.

Genotypic variation in sulphur assimilation and metabolism of onion (Allium cepa L.). II: Characterisation of ATP sulphurylase activity

To investigate the regulation of sulphur (S)-assimilation in onion further at the biochemical level, the pungent cultivar W202A and the milder cultivar Texas Grano 438 PVP (TG) have been grown in S-sufficient (S(+); 4meqS(-1)) or S-deficient (S(-); 0.1meqS(-1)) growth conditions, and tissues excised at the seedling stage (pre-bulbing; ca. 10-weeks-old) and at the mature stage (bulbing; ca. 16-weeks-old). S-supply negatively influenced adenosine-5'-phosphosulphate (APS) reductase (APR) enzyme activity in both cultivars at bulbing only, and a higher abundance of APR was observed in both cultivars at bulbing in response to low S-supply. In contrast, S-supply significantly influenced ATP sulphurylase (ATPS) activity in leaf tissues of W202A only, and only at bulbing, while an increase in abundance in response to high S-supply was observed for both cultivars at bulbing. To investigate the regulation of the ATPS enzyme activity and accumulation further, activity was shown to decrease significantly in roots at bulbing in the S-deficient treatment in both cultivars, a difference that was only supported by western analyses in W202A. Phylogenetic analysis revealed that AcATPS1 groups in a broad monocot clade with the closest sequences identified in Sorghum bicolour, Zea mays and Oryza sativa, but with some support for a divergence of AcATPS1. Detection of ATPS in leaf extracts after two dimensional gel electrophoresis (2-DE) revealed that the protein may undergo post-translational modification with a differential pattern of ATPS accumulation detected in both cultivars over the developmental progression from the seedling to the bulbing stage. Treatment of leaf extracts of W202A to dephosphorylate proteins resulted in the loss of immuno-recognised ATPS spots after 2-DE separation, although enzyme activity was not influenced. These results are discussed in terms of the tiers of control that operate at the biochemical level in the reductive S-assimilation pathway in a S-accumulating species particularly during the high-S-demanding bulbing stage.

Complex formation between recombinant ATP sulfurylase and APS reductase of Allium cepa (L.)

Recombinant ATP sulfurylase (AcATPS1) and adenosine-5'-phosphosulfate reductase (AcAPR1) from Allium cepa have been used to determine if these enzymes form protein-protein complexes in vitro. Using a solid phase binding assay, AcAPR1 was shown to interact with AcATPS1. The AcAPR1 enzyme was also expressed in E. coli as the N-terminal reductase domain (AcAPR1-N) and the C-terminal glutaredoxin domain (AcAPR1-C), but neither of these truncated proteins interacted with AcATPS1. The solid-phase interactions were confirmed by immune-precipitation, where anti-AcATPS1 IgG precipitated the full-length AcAPR1 protein, but not AcAPR1-N and AcAPR1-C. Finally, using the ligand binding assay, full-length AcATPS1 has been shown to bind to membrane-localised full-length AcAPR1. The significance of an interaction between chloroplastidic ATPS and APR in A. cepa is evaluated with respect to the control of the reductive assimilation of sulfate.

Removal of C-spine protection by A&E triage nurses: a prospective trial of a clinical decision making instrument

OBJECTIVE

To investigate if triage nurses could safely apply a set of clinical criteria, removing hard collars and spinal boards at initial triage assessment.

METHODS

The Nexus clinical decision rules were applied by trained triage nurses to patients who attended the department with cervical collars and/or on spinal boards. Patients were excluded if they were felt to be in need of immediate medical assessment. Data were collected on the time to nursing assessment, time to medical assessment and time spent restrained. Patients were followed up until discharge and their radiological diagnosis confirmed. Hospital records were checked to ensure that no patients re-presented with injuries that had been missed at initial assessment.

RESULTS

In total, 112 patients were included in the study. Clinical criteria were met in 59 patients and their collar removed at triage assessment. For low risk patients, this reflects a mean reduction in time spent restrained of 23.3 minutes (p<0.005; 95% confidence interval 20.18 to 26.54). No patient who had a collar removed was found to have a significant injury.

CONCLUSIONS

Simple criteria can be applied by accident and emergency triage nurses to allow safe removal of cervical collars and spinal boards. The reduced time patients spent immobilised represents an important improvement in patient care.

Antiangiogenic potential of camptothecin and topotecan

PURPOSE

To determine the inhibitory nature of sublethal doses of camptothecin (CPT) and topotecan (TPT) treatments on normal human endothelial cells in vitro, as well as the in vivo antiangiogenic activity as compared to another antiangiogenic compound, TNP-470 and to a nonspecific cytotoxic agent, cisplatin.

METHODS

Growth inhibition was determined by the crystal violet assay to measure relative cell numbers. (3)H-thymidine uptake was used to determine the inhibitory effect of CPT and TPT on DNA synthesis in vitro. Cell viability was determined using trypan blue exclusion assays. Cell cycle response to CPT was determined by flow cytometric analysis of propidium iodide-stained nuclei. In vivo inhibition of angiogenesis was determined by the disc angiogenesis system (DAS), where surgical sponge discs were placed subcutaneously in the rat dorsum and the ability of systemic treatment with liposomal CPT (LCPT), TPT, TNP-470 or cisplatin to inhibit vascular growth into the discs was evaluated. Quantitation of vascular growth was determined using toluidine blue staining of sectioned discs followed by digital image analysis.

RESULTS

Treatment with 50 nM CPT or TPT inhibited human umbilical venular endothelial cell (HUVEC) growth as shown by crystal violet staining, but was not cytotoxic to the cells. This was evidenced by the fact that cell numbers did not increase or decrease with treatment, but remained static while cells were viable for over 96 h posttreatment. (3)H-thymidine uptake in HUVEC was inhibited as early as 5 min, reached a maximum inhibition at 24 h and lasted over 96 h posttreatment. Cell cycle analysis of CPT-treated HUVEC showed arrest in S-phase at 12 h with a concurrent decrease in population of cells in G(1). Accumulation of cells at the G(2)/M-phase was discernible at 24 h along with the S-phase inhibition. Treatment of rats with 1 mg/kg LCPT or TPT every other day for 14 days resulted in approximately 30% inhibition of vascular growth into the discs. This inhibition was similar to the inhibition seen with TNP-470, an established and potent angiogenic inhibitor. In contrast, cisplatin was not as effective in inhibiting vascular growth into the discs.

CONCLUSIONS

In this work we showed that CPT and TPT inhibit human endothelial cell growth in vitro in a non-cytotoxic manner and that this inhibition lasts more than 96 h after drug removal. We also showed that LCPT and TPT, unlike a nonspecific cytotoxic agent, cisplatin, are as effective as TNP-470 in inhibiting angiogenic growth in the in vivo disc angiogenesis model. From this observation we propose that in addition to their proven tumoricidal activities, camptothecins may have an indirect in vivo antitumor effect mediated through the inhibition of angiogenesis.

A filing system for medical literature

The author reviews the types of systems available for personal literature files and makes specific recommendations for filing systems for family physicians. A personal filing system can be an integral part of family practice, and need not require time out of proportion to the worth of the system. Because it is a personal system, different types will suit different users; some systems, however, are more reliable than others for use in family practice. (Can Fam Physician 1988; 34:425-433.).

Obstetrical anaesthesia at Winnipeg Women's Hospital 1975-83: anaesthetic techniques and complications

The obstetrical anaesthesia experience of the Winnipeg Women's Hospital from 1975 to 1983 was reviewed (n = 22,925 infants). Use of narcotics in labour for analgesia decreased from 38.7 to 18.3 per cent of the deliveries. For analgesia during spontaneous vaginal deliveries, epidural anaesthesia increased from 6.0 to 24.0 per cent, inhalational analgesia decreased from 53.7 to 3.2 per cent while "no anaesthetic intervention" rose from 40.3 to 72.8 per cent. Use of epidural anaesthesia for Caesarean section increased from 58.7 to 82.6 per cent. The most common acute complications of anaesthesia were hypotension and inadvertent dural puncture during epidural catheterization. The incidence of hypotension decreased from 28.3 to 17.4 per cent during the nine-year period. Dural puncture decreased from 4.7 to 1.1 per cent of all epidural administrations. Postpartum complaints (that were thought to be related to anaesthesia) were mainly headache, back pain and sore throat. The incidence of these complaints also decreased over the study period.

The effect of ketamine anaesthesia on the acidotic fetal lamb

The following study in pregnant ewes was done to examine the effects of ketamine-oxygen anaesthesia on the fetal lamb made acidotic by partial occlusion of the umbilical cord. Fifteen pregnant ewes were instrumented under general anaesthesia to allow continuous measurement of maternal and fetal mean arterial pressure and pulse rate and for withdrawal of arterial blood samples for blood gas analysis. An occlusion loop was loosely secured around the umbilical cord. Following a recovery period of 48 hours, a tracheostomy was performed on each ewe. After a control period, the umbilical occlusion loop was slowly inflated until fetal pH had decreased to 7.12-7.15. Following inflation the animals were divided into groups A and B. Group A received no anaesthesia. In Group B, the ewes received ketamine 3 mg X kg-1 intravenously and controlled ventilation with FIO2 of 1.0. After ten minutes ketamine 1 mg X kg-1 was given. In both groups radioactive microspheres were injected into the fetus at 0, 5, and 15 minutes. Ketamine anaesthesia in the pregnant ewe abolished the fetal hypertension and bradycardia produced by partial cord occlusion. All fetuses survived the 15 minutes of ketamine anaesthesia and there were no significant changes in arterial blood gases or pH. Blood flows determined by the microsphere method to the brain, heart, and kidneys were not significantly altered by ketamine. We conclude that ketamine-oxygen anaesthesia does not cause further deterioration in the acidotic fetal lamb.

Paresthesias and motor dysfunction after labor and delivery

The incidence of paresthesias and motor dysfunction associated with 23,827 deliveries at Winnipeg Women's Hospital during a 9-yr period (1975-1983) was 18.9/10,000 deliveries. All the symptoms resolved within 72 hr after supportive therapy only. The frequency of paresthesias and motor dysfunction was greater in primiparas, women who had forceps- or vacuum-assisted deliveries, and women who had epidural or general anesthesia. Significant neurologic deficits after labor and delivery with or without epidural anesthesia were rare. Epidural anesthesia is a safe technique in this regard.

Isoflurane potency and cardiovascular effects during short exposures in the foetal lamb

Isoflurane is a relatively new volatile anaesthetic in clinical practice and increasing use for obstetrical patients might be expected. A previous study demonstrated that a 60-90 minute exposure of the foetus to isoflurane resulted in a significant fall in foetal cardiac output with development of foetal acidosis. To determine the cardiovascular effects of a shorter exposure of the foetal lamb to isoflurane and the potency (MAC) of isoflurane in the foetus, the following study was done. Eleven pregnant ewes were surgically prepared by placing indwelling arterial and venous catheters into the mother and foetus. After a 48-hour recovery period, isoflurane, two per cent in oxygen, was administered to six ewes via a tracheostomy for 30 minutes. Foetal cardiac outputs and regional blood flows were measured by the microsphere method. In five ewes the concentration of isoflurane was varied and MAC determinations were done on both ewe and foetus. Arterial blood levels of isoflurane were used to determine foetal MAC. Exposure to isoflurane resulted in a significant decrease in maternal and foetal mean arterial blood pressures and in foetal heart rate. Exposures up to 30 minutes did not result in foetal acidosis or a significant fall in cardiac output. Maternal and foetal MAC for isoflurane were determined to be 0.86 and 0.34 per cent respectively.

Ovine fetal urine production following maternal intravenous furosemide administration

The response of the ovine fetus to maternal furosemide administration was studied in six chronically catheterized fetal lamb preparations. These studies indicate that in the chronic sheep model maternally administered diuretics do not augment fetal urine production. Additionally, passage of the drug from the maternal intravascular compartment to the fetal intravascular compartment could not be demonstrated. It is suggested that on the basis of these data, the results of the "Lasix challenge test" should be interpreted with caution when they are used to evaluate human fetal renal function.

Lorazepam and diazepam as adjuncts to epidural anaesthesia for caesarean section

Lorazepam 0.05 mg X kg-1 and diazepam 0.1 mg X kg-1 administered intravenously were compared as sedatives for 42 patients undergoing Caesarean Section under epidural anaesthesia. After receiving the drug, 15 per cent of the diazepam patients and 32 per cent of the lorazepam patients were still agitated. Ten per cent of the diazepam patients and 36 per cent of the lorazepam patients had severe symptoms of delirium. These included hallucinations, confusion, agitation, restlessness, inappropriate weeping and repetitive hand movements. Memory impairment was greater with lorazepam. Thirty-five per cent of the diazepam patients had pain at the injection site. None of the lorazepam patients had such pain. Respiratory rate, heart rate and mean blood pressure did not change significantly in either group. Half the patients who had been given lorazepam had side effects that were bothersome enough to cause them to complain the following day. Lorazepam and diazepam were both unsatisfactory as sedatives for patients having Caesarean Section.

Cimetidine premedication in elective caesarean section

A single intramuscular injection of Cimetidine was compared to oral antacid premedication in 17 patients undergoing elective Caesarean section. Seven patients in the Cimetidine group and four in the antacid group had gastric volumes in excess of 50 ml after induction of anaesthesia, while two patients in each group had gastric pH less than 2.5 after induction. Cimetidine was as effective as antacid in raising gastric pH but neither was completely reliable. This study reconfirms the high gastric volumes in pregnant patients with the need for preventative measures against aspiration during the induction of anaesthesia.

Prophylactic blood patch does not prevent post lumbar puncture headache

Of 86 patients in whom accidental puncture of the dura occurred during insertion of a needle for induction of epidural analgeisa for labour and delivery, 11 received a prophylactic blood patch at the completion of delivery. Of the 75 patients with no prophylactic blood patch, 59 per cent developed post-lumbar-puncture headache, while 54 per cent of those who had a prophylactic blood patch developed headache. The prophylactic blood patch appears to have no value in preventing post-lumbar-puncture headache in this small group of patients.

Gastric volume and pH in out-patients

We measured the volume and pH of the gastric content of 21 out-patients and 21 in-patients under general anaesthesia. Gastric tubes were inserted after induction of anaesthesia, and gastric fluids were withdrawn for pH determinations. Gastric volumes were measured by a dilution technique using polyethylene glycol as the indicator and also by measurement of the volume aspirated through a gastrict tube. Out-patients had a mean gastric volume of 69 +/- 17 ml while in-patients had a mean volume of 33 +/- 4 ml. The average gastric pH for the out-patients was 1.8 +/- 0.2 and for the in-patients 2.0 +/- 0.3. Four out-patients had more than 75 ml of gastric fluid of pH less than 2.0. Aspiration through a gastrict tube did not empty the stomach completely and the volume thus obtained gave a falsely low estimate of the gastric volume.

Foetal deterioration following thiopentone-nitrous oxide anaesthesia in the pregnant ewe

Six pregnant sheep were chronically prepared with indwelling catheters in maternal and foetal vessels and a flow probe around a maternal uterine artery. They were anaesthetized the following day with thiopentone and nitrous oxide (70 per cent)--oxygen (30 per cent) maintenance with tracheal intubation. Maternal uterine blood flow fell about 20 per cent following induction of anaesthesia. This resulted from uterine vasoconstriction which, in turn, probably resulted from maternal catecholamine release during light anaesthesia. The foetus in utero developed a mixed metabolic and respiratory acidosis and a fall in oxygen saturation. The possibility that light maternal anaesthesia increases rather than decreases neonatal depression is discussed.