Pilot randomised experimental study evaluating isopropyl alcohol and UVC radiation in the disinfection of healthcare workers' smartphones

Smartphones in medical settings pose infection risks due to harbouring pathogenic bacteria. This pilot study assesses the effectiveness duration of sanitisation methods, focusing on 70% isopropyl alcohol wipes and UVC boxes, aiming to obtain preliminary data on the reduction in Total Bacterial Load 3 hours post-sanitisation. A randomised monocentric trial with two intervention arms (wipes and UVC boxes) was designed. As participants, healthcare workers from three wards at Fondazione Policlinico Universitario "A. Gemelli" IRCCS Hospital were recruited, stratified by ward, and block randomised within each ward to control confounders. Seventy-one healthcare workers, mostly nurses (62%) were included in the study. Initial bacterial load reduction was significant with both disinfection techniques, but after 3 hours both methods showed increased bacterial levels, with wipes displaying potentially higher residual efficacy (p=0.056). To adequately size a trial (89% power, significance level 0.05) for assessing the residual efficacy of alcohol-impregnated wipes compared to UVC boxes at 3 hours post-sanitisation, 503 professionals per group were required. This study highlights the necessity for guidelines on hospital smartphone sanitisation and educational initiatives for healthcare workers and patients. Further studies, adequately sized, are necessary to determine optimal sanitisation intervals and assess pathogen transmission risks.

Canine glioblastoma-derived extracellular vesicles as precise carriers for glioblastoma imaging: Targeting across the blood-brain barrier

The treatment of glioblastoma (GBM) faces significant challenges due to the difficulty of delivering drugs through the blood-brain barrier (BBB). Extracellular vesicles (EVs) have emerged as potential carriers for targeted drug delivery to brain tumors. However, their use and distribution in the presence of an intact BBB and their ability to target GBM tissue are still under investigation. This study explored the use of EVs for GBM targeting across the BBB. Canine plasma EVs from healthy dogs and dogs with glioma were isolated, characterized, and loaded with diagnostic agents. Biodistribution studies were conducted in healthy murine models and a novel intranasal model that preserved BBB integrity while initiating early-stage GBM growth. This model assessed EVs' potential for delivering the contrast agent gadoteric acid to intracranial tumors. Imaging techniques, such as bioluminescence and MRI, confirmed EVs' targeting and delivery capabilities thus revealing a selective accumulation of canine glioma-derived EVs in brain tissue under physiological conditions. In the model of brain tumor, MRI experiments demonstrated the ability of EVs to accumulate gadoteric acid within GBM to enhance contrast of the tumoral mass, even when BBB integrity is maintained. This study underscores the potential of EVs derived from glioma for the targeted delivery of drugs to glioblastoma. EVs from dogs with glioma showed capacity to traverse the BBB and selectively accumulate within the brain tumor. Overall, this research represents a foundation for the application of autologous EVs to precision glioblastoma treatment, addressing the challenge of BBB penetration and targeting specificity in brain cancer therapy.

Comparison of the Trachea in Normocephalic versus Brachycephalic Cats on the Basis of CT-Derived Measurements

Tracheal hypoplasia is a major concern in brachycephalic dogs, but there is no consensus for the trachea in brachycephalic cats. We aimed to compare tracheal length and diameter between normo- and brachycephalic cats using computed tomography (CT) image measurements and evaluate their usefulness in tracheostomy planning. A total of 15 normocephalic and 14 brachycephalic cats were included in the study. Tracheas of normocephalic cats were significantly longer compared with brachycephalic cats. No difference was detected in tracheal diameter between normocephalic and brachycephalic cats. Both groups had a lateral diameter significantly larger than the dorsoventral diameter at the level of the cranial end of the manubrium sterni and at the level of the second rib. Normocephalic and brachycephalic cats' tracheas have the same dorsoventral flattening at the level of the cranial end of the manubrium sterni and at the level of the second rib. The location between the 4th and 5th cervical vertebrae seems the best place to perform a tracheostomy in cats due to its round shape and easily accessible anatomical location. No sign of tracheal hypoplasia in brachycephalic cats was detected. Finally, 7 mm appears to be an adequate diameter for the tracheal tubes used to perform feline tracheostomies.

Persistent mullerian duct syndrome in a dog

INTRODUCTION

This case report describes a 14-year-old, male castrated York Shire Terrier, which was presented due to stranguria and tenesmus. An abdominal computed tomography (CT) scan raised a high suspicion of a persistent mullerian duct. During laparotomy structures were found that were suspected to be a persistent ovary and uterus. The abnormal uterus was filled with fluid and had a blind end on both sides. The abnormal structures were surgically removed and pathologically examined. Pathology confirmed a persistent mullerian duct. The patient recovered well from the surgery and was able to urinate spontaneously the same day and was discharged the next day.

CT measurements of tracheal diameter and length in normocephalic cats

OBJECTIVES

The aim of this study was to measure the tracheal dimensions of normocephalic cats using CT.

METHODS

CT images of 15 client-owned normocephalic cats were retrospectively evaluated to measure the length of the feline trachea. Transverse and vertical inner diameters were measured in five different tracheal regions, and the cross-sectional area of the tracheal lumen was calculated for each point of measurement. Descriptive statistics were applied using a two-tailed t-test.

RESULTS

The mean ± SD length of the trachea was 125.13 ± 14.41 mm. Male cats had significantly larger tracheas than female cats. The transverse diameter first increased by 0.94 mm between the most cranial point of measurement and the middle of the trachea. It then decreased by 1.38 mm between the middle of the trachea and the most caudal point of measurement. The vertical diameter decreased by 1.16 mm between the first point of measurement and the penultimate point, and then increased by 0.06 mm between the penultimate point of measurement and the end of the trachea. The two different diameters resulted in an elliptical trachea shape.

CONCLUSIONS AND RELEVANCE

The feline trachea was circular only at its cranial and caudal ends, and elliptical with a dorsoventral flattening along the rest of its length. Vertical and transverse diameters varied along the entire length. Tracheal shape differences should be considered when performing permanent tracheostomy, tracheal anastomosis or stenting in cats.

Feline primary nonhematopoietic malignant liver tumours: A multicenter retrospective study (2000-2021)

There is scant literature on primary nonhematopoietic malignant liver tumours (PMLT) in cats. In this retrospective study, medical data of 40 cats diagnosed with PMLT were reviewed over a period of 22 years (2000-2021). The most frequent epithelial tumours were hepatocellular (42.5%) and bile duct carcinomas (32.5%), only six (15%) cats had mesenchymal tumours. The median age was 13 years and clinical signs commonly included ano-/hyporexia (62.5%), apathy/lethargy (52.5%), weight loss (42.5%) and vomiting (35%). At initial diagnosis, metastases were confirmed in 1 (2.5%) and suspected in three (7.5%) cats. Massive was the most frequent morphology (75%). Most intrahepatic tumours were left-sided (54.2%) with the left medial lobe being primarily affected (25%). Extrahepatic tumours were rare (5%). In 34 (85%) cats, liver lobectomy was performed (surgery group), four (10%) were treated palliatively (non-surgery group), and two (5%) received no treatment. Intraoperative complications occurred in 11.8% with four (15.4%) postoperative deaths. Recurrence was detected in 28.6% at a median of 151 days (range, 79-684 days), while postoperative metastases were suspected in 21.4% at a median of 186 days (range, 79-479 days). The median survival time (MST) was significantly longer in cats of the surgery group (375 days) than in the non-surgery group (16 days) (p = .002). MST was 868 days for hepatocellular compared to 270 days for bile duct carcinomas (p = .06). In summary, liver lobectomy is associated with prolonged survival times and good prognosis in cats with hepatocellular, and an acceptable prognosis in cats with bile duct carcinoma.

Microbiological surveillance post-reprocessing of flexible endoscopes used in digestive endoscopy: a national study

INTRODUCTION

Microbiological surveillance of endoscopes is a safety measure for verifying the quality of reprocessing procedures and identifying contaminated devices, but duodenoscope-related outbreaks are still reported.

AIM

To assess the effectiveness of duodenoscope reprocessing procedures in Italy.

METHODS

Between December 2019 and April 2020, data obtained from microbiological surveillance post-reprocessing in 15 Italian endoscopy units were collected. Sampling was carried out after reprocessing or during storage in a cabinet. In keeping with international guidelines and the Italian position paper, the micro-organisms were classified as high-concern organisms (HCOs) and low-concern organisms (LCOs).

FINDINGS

In total, 144 samples were collected from 51 duodenoscopes. Of these, 36.81% were contaminated: 22.92% were contaminated with HCOs and 13.89% were contaminated with LCOs [2.08% with an LCO load of 11-100 colony-forming units (CFU)/device and 0.69% with an LCO load of >100 CFU/device]. The contamination rate was 27.5% in samples collected after reprocessing, 40% in samples collected during storage in a cabinet that was compliant with EN 16442:2015 (C-I), and 100% in samples collected during storage in a cabinet that was not compliant with EN 16442:2015 (NC-I). The respective HCO rates were 15.00%, 27.27% and 66.67%. Correlation between LCO contamination and storage time was demonstrated (Spearman's rho=0.3701; P=0.0026). The Olympus duodenoscope TJFQ180V demonstrated the lowest rate of contamination (29.82%), although the contamination rate was 100% for duodenoscopes stored in an NC-I cabinet.

CONCLUSION

Microbiological surveillance, along with strict adherence to reprocessing protocols, may help to detect endoscope contamination at an early stage, and reduce the risk of duodenoscope-associated infections.

Increased Sensitivity of Computed Tomography Scan for Neoplastic Tissues Using the Extracellular Vesicle Formulation of the Contrast Agent Iohexol

Computed tomography (CT) is a diagnostic medical imaging modality commonly used to detect disease and injury. Contrast agents containing iodine, such as iohexol, are frequently used in CT examinations to more clearly differentiate anatomic structures and to detect and characterize abnormalities, including tumors. However, these contrast agents do not have a specific tropism for cancer cells, so the ability to detect tumors is severely limited by the degree of vascularization of the tumor itself. Identifying delivery systems allowing enrichment of contrast agents at the tumor site would increase the sensitivity of detection of tumors and metastases, potentially in organs that are normally inaccessible to contrast agents, such as the CNS. Recent work from our laboratory has identified cancer patient-derived extracellular vesicles (PDEVs) as effective delivery vehicles for targeting diagnostic drugs to patients' tumors. Based on this premise, we explored the possibility of introducing iohexol into PDEVs for targeted delivery to neoplastic tissue. Here, we provide preclinical proof-of-principle for the tumor-targeting ability of iohexol-loaded PDEVs, which resulted in an impressive accumulation of the contrast agent selectively into the neoplastic tissue, significantly improving the ability of the contrast agent to delineate tumor boundaries.

Preliminary Studies on the Intrahepatic Anatomy of the Venous Vasculature in Cats

Hepatic surgeries are often performed in cats to obtain a disease diagnosis, for the removal of masses, or for the treatment of shunts. Whereas the vascular anatomy of the liver has been studied in dogs, such evidence is lacking in cats. The current study used corrosion casts of portal and hepatic veins and computed tomography (CT) analysis of the casts to identify and describe the intrahepatic anatomy in healthy cat livers (n = 7). The results showed that feline livers had a consistent intrahepatic portal and venous anatomy, with only minor disparities in the numbers of secondary and tertiary branches. The feline portal vein consistently divided into two major branches and not three, as previously described in the literature for cats. The finding of a portal vein originating from the right medial lobe branch leading to the quadrate lobe in 4/7 specimens is a novelty of the feline anatomy that was not previously described in dogs. Partial to complete fusion of the caudate process of the caudate and the right lateral lobe, with a lack of clear venous separation between the lobes, was present in two specimens. These findings allowed a detailed description of the most common intrahepatic venous patterns in cats. Further anatomical studies should be encouraged to confirm the present findings and to investigate the utility of this information in surgical settings.

Feline gastrointestinal eosinophilic sclerosing fibroplasia presenting as a rectal mass

Case summary

A 9-year-old neutered male cat was referred owing to dyschezia and weight loss. Abdominal CT revealed a heterogeneous mass in the rectum and thickening of one caudal mesenteric lymph node. The mass induced a focal rectal obstruction. Cytological evaluation of fine-needle aspirates showed signs of mixed inflammation for the rectal mass and a reactive lymph node. Because a definite diagnosis was not achieved, complete resection of the mass via a dorsal approach to the rectum was attempted. Histopathology confirmed complete removal and diagnosed feline gastrointestinal eosinophilic sclerosing fibroplasia (FGESF). The cat was treated with psyllium husks and lactulose after surgery. In the postoperative year, the owner reported normal behaviour, food intake and defecation of the patient. Dyschezia reoccurred 14 months after surgery. Imaging revealed recurrence of a rectal mass. Owing to clinical deterioration, the owner elected for euthanasia.

Relevance and novel information

This is the first report of rectal FGESF with dyschezia and weight loss as the main clinical signs. The case demonstrates an acceptable outcome for more than 1 year without additional immunosuppressive therapy, and emphasises that FGESF must be considered as a differential diagnosis for rectal masses in cats.

Anaesthetic Management of a Labrador Retriever Undergoing Adrenalectomy for Phaeochromocytoma Excision, a Case Report

Perioperative management of cases undergoing phaeochromocytoma removal should aim at normalising blood pressure and heart rate, restoring volume depletion, and preventing catecholamine release induced by surgical manipulation. In this case report, a novel pharmacological approach in a dog undergoing surgical tumour excision is described. A 7-year-old 25-kg spayed female Labrador Retriever presented for repeated episodes of generalised weakness, pale mucous membranes, tachycardia, tremor, panting, vomiting, and hypertension over the last month was referred for surgical treatment of a left-sided adrenal tumour with invasion of the caudal vena cava. Severe hypertensive episodes occurred repeatedly, starting early during the anaesthetic period, while clipping and cleaning the abdominal area, and continued intraoperatively when the tumour was handled. Moderate hypotension occurred once the tumour was isolated and worsened during temporary caudal vena cava flow interruption and cavotomy. The patient was treated preoperatively with phenoxybenzamine to prevent hypertensive crises. Intraoperatively, magnesium sulphate and urapidil were used to control blood pressure. This treatment was effective in reducing the magnitude of blood pressure spikes but not sufficient to prevent hypertensive peaks, especially during tumour manipulation. Hypotension was treated with synthetic colloid and crystalloid boli, and noradrenaline continuous infusion. Blood transfusion was performed in response to acute bleeding during cavotomy. The dog recovered successfully from anaesthesia and its quality of life was deemed excellent by the owner at the last follow up, 22 months after surgery. The histopathology confirmed the diagnosis of phaeochromocytoma with an invasion of the phrenicoabdominal vein. In the present case, we obtained a successful outcome but failed to provide haemodynamic stability throughout the procedure.

From infections to preventive actions monitoring in health facilities: an experience on MDROs

 

Healthcare-Associated Infections (HAIs) and Antimicrobial Resistance (AMR) involve high costs both in health and economic terms for patients and health systems. Implementing Infection Prevention and Control (IPC) programs is critical to decrease infectious agents' transmission in healthcare settings. The aim of this study is to assess if the monitoring of Contact Precautions could decrease the incidence of Multi-Drug Resistant Organisms (MRDOs) infections. This pilot study was conducted in a teaching hospital in Rome. A checklist of 16 items was developed to assess the compliance to Contact Precautions in 11 hospital wards in which MRDOs were detected between November and December 2020. It was administered on-site both interviewing healthcare professionals and through direct observation. A paired t-test with α = 5% was used to compare the number of alert organisms in the first quarter of 2020 respect to the first quarter of 2021 before and after implementing the surveillance checklist. A total of 30 checklists were analyzed. The rate of compliance to Contact Precautions was high for the proper use of personal protective equipment (100%), the intensified room cleaning (100%) and the presence of isolation mark (100%), while it was low for the active screening of contacts (53%). Mean MDROs infections rate decreased from 4.94 to 4.37 for every 1000 hospitalization day, with an average decrease of 0.57. However, the paired t-test showed that there was no statistically significant difference between the mean number of MDROs infections before and after the implementation of the checklist (p > 0.05). Despite the good adherence to IPC program, the low infection rate decrease, is probably due to the impact of COVID-19 on the HAIs surveillance and prevention practices. Even if the check-list administration could be a useful tool to reduce MDROs infections, it should be associated to other prevention strategies during the COVID-19 pandemic in order to achieve a successful outcome.

Key messages

Preventing Healthcare-Associated Infections represents a priority public health challenge in order to improve patient safety and health system economic sustainability.

The COVID-19 pandemic has shown that healthcare facilities should enhance efforts in their IPC programs to reduce Healthcare-Associated Infections.

Total laryngectomy in a cat with a laryngeal peripheral nerve sheath tumor

OBJECTIVE

To report the surgical technique and outcome of total laryngectomy in a single clinical case.

STUDY DESIGN

Case report.

ANIMAL

A 5-year-old female spayed domestic shorthair cat.

METHODS

A cat presented for acute, severe respiratory distress caused by an invasive laryngeal mass. Incisional biopsy was indicative of sarcoma. Computed tomography of head, neck, and thorax was performed revealing no evidence of metastasis. A total laryngectomy and permanent tracheostomy were performed, and the cat could breathe without difficulties immediately postoperatively. Histopathology confirmed a laryngeal low-grade peripheral nerve sheath tumor (PNST).

RESULTS

Surgical margins were free of tumor cells. Surgical revision of the tracheostomy stoma due to obstructive granulation tissue was necessary 24 days after the initial surgery. Nine days after revision surgery, the cat was discharged from the hospital. No evidence of local recurrence or metastasis was detected on repeat computed tomography of the head, neck, and thorax at 6 months, nor on chest radiographs at 12 months postoperatively. At the time of writing (13 months postoperatively), the cat is still alive with a good quality of life.

CONCLUSION

Total laryngectomy with permanent tracheostomy allowed the complete removal of an obstructive laryngeal PNST and provided a good quality of life in a cat.

CLINICAL SIGNIFICANCE

To the authors' knowledge, this case report represents the first detailed description of the surgical procedure and clinical outcome for a total laryngectomy in a cat.

Characterization of canine epidermal organoid cultures by immunohistochemical analysis and quantitative PCR

BACKGROUND

Keratinocyte organoids can be used as a tool to evaluate epidermal structure, function and dysfunction.

OBJECTIVES

To optimize the canine keratinocyte organoid system and produce organoids that are structurally equivalent to in vivo canine epidermis, in order to enable studies that focus on epidermal diseases and diseases resulting from an impaired epidermal barrier.

ANIMALS

Skin biopsies were obtained from five recently euthanized dogs of different breeds with no skin abnormalities.

METHODS AND MATERIALS

Cells derived from microdissected interfollicular epidermis were seeded in basement membrane extract and epidermal organoids were grown under different media conditions. Organoids were characterized to assess cell morphology and architecture in haematoxylin and eosin-stained slides and expression of selected epidermal markers (keratin 5, keratin 10, loricrin and filaggrin) by immunohistochemical analysis and quantitative reverse transcription PCR.

RESULTS

The selected epidermal markers were expressed in the same epidermal layers in the organoids cultured in expansion medium and differentiation medium as in normal interfollicular epidermis, yet restriction to the distinct layers was best achieved with expansion medium. Comparison of the mRNA expression levels of these markers revealed that relative expression is similar in organoids cultured in expansion medium and normal canine epidermis, while it differs in organoids cultured in differentiation medium.

CONCLUSION AND CLINICAL IMPORTANCE

Organoids cultured in expansion medium have an equivalent structure to the interfollicular epidermis and express key marker proteins in similar proportions. Epidermal organoids are therefore a promising in vitro model to study epidermal structure, function and dysfunction.

A complex histopathological challenge: suspicion of an osteoblastoma-like osteosarcoma arising from the second thoracic vertebra in a cat

BACKGROUND

Reports of osteoblastic tumours are limited to a few case reports in veterinary medicine. Osteoblastoma-like osteosarcoma has been accepted by the World Health Organization as an intermediate form between an osteosarcoma and osteoblastoma. This type of tumour indicates an osteosarcoma, that may resemble osteoblastoma clinically, histologically, and radiologically and have the capability for metastasis. Osteoblastoma-like osteosarcoma has not been described in veterinary medicine so far.

CASE PRESENTATION

An eight-year old cat was presented due to progressive ataxia and paraparesis of the pelvic limbs. Imaging confirmed a well-defined, extradural mass originating from the spinous process of the second thoracic vertebra (T2) leading to severe compression of the spinal cord. Decompressive cytoreduction was achieved by removal of the mass after dorsal laminectomy of T1. After recovering from an acute worsening 3.5 weeks after surgery, the cat had an improved neurological status and the dorsal compression was resolved at follow-up 8 months later. A focal contrast enhancing lesion was still evident at the base of T2 spinous process and lung metastasis was additionally suspected. Based on histopathological, radiographic, and clinical features, an "osteoblastoma-like osteosarcoma" was suspected.

CONCLUSIONS

To the best of our knowledge, this is the first description of this tumour in veterinary medicine. In addition, this case report highlights the difficulty in the diagnosis and definition of osseous neoplasia in cats and provides a literature review.

Effect of ClO2 on the distribution of Legionella pneumophila serogroups in a Teaching Hospital

The prevention of Legionella colonization of water systems is one of the goals of hospital management. Among chemical disinfection methods, chlorine dioxide (ClO2) has been largely used to control Legionella in water systems. We analysed the distribution of Legionella pneumophila serogroups (sg) and Legionella other spp before (PRE) and after (POST) installation of chlorine dioxide (ClO2) continuous disinfection systems in a Teaching Hospital in Rome.

According to the Italian National Guidelines, our surveillance plan involved a systematic sampling of the water system. The sampling was performed from Jan. 2010 to Dec. 2019. From 2011 to 2019, ClO2 continuous disinfection systems were installed in all hot water system of the hospital, and maintained at a concentration of 0.25 mg/l at the end point. The isolated strains of Legionella were first serotyped using a kit that identifies sg1, other species and that discriminate sg from 2 to 15.

1505 hot water samples were collected from the Hospital and analysed. 363 samples are PRE and 1142 are POST activation of ClO2. Only the 16.74% of monitored sampling points were colonized by Legionella during the study period. This percentage decrease from 31.40% of PRE samples, to 12.08% of POST samples (p ≤ 0.000). The sg isolated were: sg3 (60.31%), sg8 (17.12%), sg1 (16.73%), sg6 (1.95%) and other species (3.89%). Comparing the distribution of sg between the PRE and POST samples, the sg8 showed a high increase (+136.84%) and the sg3 a slight decrease (-17.94%). These variations were statistically significative.

The results showed a predominance of Legionella pneumophila sg3, compared to what was observed in a multicenter study conducted between different hospitals of various regions of Italy, where sg6 was the major isolate. The ClO2 affect the distribution of sg, in particular for sg8. This interesting result will be further investigated.

Key messages

Our data deriving from an environmental monitoring plan, show that the ClO2 affects the distribution of Legionella’s serogroups. The ClO2 reduces the percentage of samples colonized by Legionella. The ClO2 reduces the percentage of samples colonized by Legionella.

Influence of treatment on the outcome of dogs with incompletely excised grade-2 mast cell tumors

INTRODUCTION

In this study we compared the outcomes of dogs with incompletely-excised grade-2 mast cell tumors (incompletely- excised grade-2 MCTs) either adjuvantly treated or not. Dogs with a grade-2 mast cell tumour (MCT) excised either incompletely or with narrow (.

Substrate selectivity and pH dependence of KAAT1 expressed in Xenopus laevis oocytes

When expressed in Xenopus oocytes KAAT1 increases tenfold the transport of l-leucine. Substitution of NaCl with 100 mm LiCl, RbCl or KCl allows a reduced but significant activation of l-leucine uptakes. Chloride-dependence is not strict since other pseudohalide anions such as thyocyanate are accepted. KAAT1 is highly sensitive to pH. It can transport l-leucine at pH 5.5 and 8, but the maximum uptake has been observed at pH 10, near to the physiological pH value, when amino and carboxylic groups are both deprotonated. The pH value mainly influences the V(max) in Na(+) activation curves and l-leucine kinetics. The kinetic parameters are K(mNa) = 4.6 +/- 2 mm, V(maxNa) = 14.8 +/- 1.7 pmol/oocyte/5 min for pH 8.0 and K(mNa) = 2. 8 +/- 0.7 mm, V(maxNa) = 31.3 +/- 1.9 pmol/oocyte/5 min for pH 10.0. The kinetic parameters of l-leucine uptake are: K(m) = 120.4 +/- 24. 2 microm, V(max) = 23.2 +/- 1.4 pmol/oocyte/5 min at pH 8.0 and K(m) = 81.3 +/- 24.2 microm, V(max) = 65.6 +/- 3.9 pmol/oocyte/5 min at pH 10.0. On the basis of inhibition experiments, the structural features required for KAAT1 substrates are: (i) a carboxylic group, (ii) an unsubstituted alpha-amino group, (iii) the side chain is unnecessary, if present it should be uncharged regardless of length and ramification.

Simultaneous measurements of ionic currents and leucine uptake at the amino acid cotransporter KAAT1 expressed in Xenopus laevis oocytes

The transport properties of the intestinal amino acid cotransporter KAAT1, heterologously expressed in Xenopus oocytes, were studied using simultaneous voltage-clamp and tritiated leucine uptake measurements. While addition of 1 mM leucine to oocytes kept at -80 mV in presence of Na(+) or K(+) caused an increase in holding current, in presence of Li(+) the current was reduced. Uptake measurements in voltage-clamp conditions showed that a comparable accumulation of amino acid occurred in all three ionic conditions and irrespective of the direction and amount of the current change. The ratio of moles of transferred charge to moles of transported amino acid ranges from 1.45 for K(+) to 3.52 for Li(+). A hypothetical interpretation involving the coexistence of two populations of transporters, one operating in the uncoupled mode and the other in the substrate transport mode is discussed.

Ion binding and permeation through the lepidopteran amino acid transporter KAAT1 expressed in Xenopus oocytes

1. The transient and steady-state currents induced by voltage jumps in Xenopus oocytes expressing the lepidopteran amino acid co-transporter KAAT1 have been investigated by two-electrode voltage clamp. 2. KAAT1-expressing oocytes exhibited membrane currents larger than controls even in the absence of amino acid substrate (uncoupled current). The selectivity order of this uncoupled current was Li+ > Na+ approximately Rb+ approximately K+ > Cs+; in contrast, the permeability order in non-injected oocytes was Rb+ > K+ > Cs+ > Na+ > Li+. 3. KAAT1-expressing oocytes gave rise to 'pre-steady-state currents' in the absence of amino acid. The characteristics of the charge movement differed according to the bathing ion: the curves in K+ were strongly shifted (> 100 mV) towards more negative potentials compared with those in Na+, while in tetramethylammonium (TMA+) no charge movement was detected. 4. The charge-voltage (Q-V) relationship in Na+ could be fitted by a Boltzmann equation having V of -69 +/- 1 mV and slope factor of 26 +/- 1 mV; lowering the Na+ concentrations shifted the Q-V relationship to more negative potentials; the curves could be described by a generalized Hill equation with a coefficient of 1.6, suggesting two binding sites. The maximal movable charge (Qmax) in Na+, 3 days after injection, was in the range 2.5-10 nC. 5. Addition of the transported substrate leucine increased the steady-state carrier current, the increase being larger in high K+ compared with high Na+ solution; in these conditions the charge movement disappeared. 6. Applying Eyring rate theory, the energy profile of the transporter in the absence of organic substrate included a very high external energy barrier (25.8 RT units) followed by a rather deep well (1.8 RT units).