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Biomedical subjects

V Thomas

Publications and source records attributed to V Thomas.

At least 73 records · Page 4Linked to original sources
PubMed1996

Effects of Hydrophilization and Immobilization on the Interfacial Behavior of Immunoglobulins.

The adsorption and immobilization of rabbit anti-human immunoglobulin (rabbit IgG), as well as the effects of rinsing with buffer and addition of bovine serum albumin (BSA) or human IgG on the amount and reactivity of bound rabbit IgG, were investigated with ellipsometry, total internal reflection fluorescence spectroscopy (TIRF), and enzyme immuno assay (EIA). It was found that although rabbit IgG readily adsorbs at hydrophobic hexamethyldisiloxane (HMDSO) plasma polymer surfaces, a substantial fraction of the adsorbed protein molecules is desorbed upon rinsing with buffer. BSA was found to adsorb readily at the surfaces obtained after rinsing, although also this protein desorbed to a large extent (about 60%) upon further rinsing with buffer. The adsorption of BSA causes a further reduction in the amount of rabbit IgG adsorbed. Immobilization of rabbit IgG to acrylic acid (AA) plasma polymer surfaces, achieved by covalent coupling via a strongly adsorbed PEG-PEI copolymer, was found to overcome the problem of the desorption of rabbit IgG upon rinsing with buffer or addition of BSA. Furthermore, nonspecific adsorption was virtually absent after immobilization. However, covalently bound rabbit IgG reacted strongly with human IgG, as observed by ellipsometry, TIRF, and EIA. The immobilization of rabbit IgG to hydrophilized surfaces was found to facilitate the interpretation of EIA results.

Journal Article↗
PubMed1996

Assessment of procedural memory in Parkinson's disease.

1. Findings in cognitive psychology and neuropsychology have led to consider the existence of several mnestic systems. This study focuses on a now clearly established distinction between the procedural and the declarative memories. 2. The aim of the present study was to try and determine which of the two acquisition steps (learning and automation) is affected by Parkinsonians' mnestic difficulties, and to verify if these difficulties are linked to the skill content (declarative or motor). 3. To answer these questions, 20 Parkinsonians under treatment underwent specific tests: the maze test and the arithmetic alphabet test. 4. Results show that, by comparison with 20 matched healthy individuals, the deficiencies observed in Parkinson's disease affect both the declarative and the motor skills. In addition, Parkinsonians suffer difficulties in both acquisition steps: learning and automation. 5. These results could account for the cognitive and motor disturbances observed in Parkinson's disease; these abnormalities should be among the pharmacological targets in future.

Adolescent↗
PubMed1996

Intracellular signaling of tumor necrosis factor-alpha in brain microvascular endothelial cells is mediated by a protein tyrosine kinase and protein kinase C-dependent pathway.

The intracellular signaling pathways responsible for tumor necrosis factor (TNF)-alpha stimulation of lymphocyte adhesion to brain microvascular endothelial cells (BMEC) were studied using inhibitors of protein kinase C (bisindolylmaleimide HCl, H-7, or staurosporine), or protein tyrosine kinase (genistein). Each of these blocked the ability of BMEC to respond to TNF-alpha. In contrast, BMEC treated with H-89, an inhibitor of protein kinase A, or the adenylate cyclase inhibitor, dideoxyadenosine, responded normally to TNF-alpha. Forskolin, an adenylate cyclase agonist, significantly increased lymphocyte adhesion to BMEC. These data indicate that intracellular signaling by TNF-alpha in BMEC is mediated through a protein kinase C and tyrosine kinase dependent pathway.

Animals↗
PubMed1996

The rectus sheath block in paediatric anaesthesia: new indications for an old technique?

The rectus sheath block has been used with success for postoperative analgesia in adults. This paper reviews the anatomy of the rectus sheath, and presents our initial experience of using the block to provide intra- and postoperative analgesia in children having repair of umbilical and paraumbilical hernia. The rectus sheath block appears to be a useful technique in children, particularly for paediatric day-cases surgery.

Abdominal Muscles↗
PubMed1996

Molecular requirements for polyamines binding to the antispermine monoclonal antibody Spm8-2.

The monoclonal antispermine antibody Spm8-2 was obtained by immunizing mice with a thyroglobulin-spermine conjugate. The molecular requirements for polyamines binding to this antibody were investigated by ELISA binding and inhibition tests, using a variety of natural polyamines and synthetic polyamine analogs. Four major structural determinants are important for the binding of polyamines by the antibody: (1) terminal amino groups: N-alkylation of both terminal amino groups of the polyamines leads to an important drop in the affinity for the antibody; (2) number of methylene groups spacing the amino groups: the four carbon chains appear to present the optimum length since the antibody binds polyamines with repeats of the aminobutyl moiety more actively than their homologues with shorter or longer carbon chains; (3) number of amino groups: the affinity of Spm8-2 for free homologous polyamines varied in the following order: pentamines > tetramines > triamines > diamines, showing the importance of the number of positive charges of the polyamines in the antibody-antigen reaction; the importance of charges is further emphasized by the dependence of antibody binding on the ionic strength of the medium; (4) N-acylation of one terminal amino group: the antibody binds more actively N1-acetylspermidine than spermidine or spermine. The binding properties of Spm8-2 suggest the presence of two recognition sequences, one selective for N-acylaminopropyl moieties, the second for the aminobutyl moiety.

Acetylation↗
PubMed1996

Pharmacokinetics of marbofloxacin in dogs after oral and parenteral administration.

Six dogs were treated with a single intravenous (i.v.) dose (2 mg/kg) of marbofloxacin, followed by single oral (p.o.) doses of marbofloxacin at 1, 2 and 4 mg/kg, according to a three-way crossover design. The same experimental design was used for the subcutaneous (s.c.) route. In addition, a long-term trial involving eight dogs given oral doses of marbofloxacin at 2, 4 and 6 mg/kg/day for thirteen weeks was carried out. Plasma and urine samples were collected during the first two trials, plasma and skin samples were collected after the second of these trials. Plasma, urine and skin concentrations of marbofloxacin were determined by a reverse phase liquid chromatographic method. Mean pharmacokinetic parameters after i.v. administration were the following: t1/2 beta = 12.4 h; ClB = 0.10 L/h.kg; Varea = 1.9 L/kg. The oral bioavailability of marbofloxacin was close to 100% for the three doses. At 2 mg/kg, Cmax of 1.4 micrograms/mliter was reached at tmax of 2.5 h. Mean AUC and Cmax values had a statistically significant linear relationship with the doses administered. About 40% of the administered dose was excreted in urine as unchanged parent drug. After s.c. administration, the calculated parameters were close to those obtained after oral administration, except tmax (about 1 h) which was shorter. The mean skin to plasma concentration ratio after the long-term trial was 1.6, suggesting good tissue penetration of marbofloxacin.

Administration, Oral↗
PubMed1996

Activation of transcription at divergent urea-dependent promoters by the urease gene regulator UreR.

The Proteus mirabilis and plasmid-encoded urease loci contain seven contiguous structural and accessory genes (ureDABCEFG) and the divergently transcribed ureR, which codes for an AraC-like transcriptional activator. Previously, it was shown that the plasmid-encoded ureR to ureD intergenic region contained divergent promoters (ureRp and ureDp). Transcription from these promoters required both the effector molecule urea and the activator protein UreR. In this report, we demonstrate that the P. mirabilis urease gene cluster contains similar divergent urea- and UreR-dependent promoters. The ureR gene products from either urease locus were able to activate transcription at both the plasmid-encoded and P. mirabilis promoters. The minimal concentration of urea required to activate transcription at ureRp or ureDp from either gene cluster was approximately 4 mM. The transcriptional start sites for the plasmid-encoded and P. mirabilis divergent promoters were similar in an Escherichia coli DH5 alpha background, as determined by primer-extension analysis. However, in P. mirabilis HI4320, transcription of ureR initiated predominately at an alternative site. Physical mapping and inhibition studies were used to localize the UreR-binding sites within the plasmid-encoded ureRp and ureDp intergenic sequences to regions of 68 bp and 86 bp, respectively. Gel shift analysis demonstrated that UreR bound to a 135 bp fragment in the approximate centre of the plasmid-encoded ureR to ureD intergenic region. The results presented here suggest that the P. mirabilis and plasmid-encoded urease gene clusters utilize similar mechanisms of transcriptional activation in response to urea.

Bacterial Proteins↗
PubMed1996

Effect of chronic cold exposure on Na-dependent D-glucose transport along small intestine in ducklings.

In conditions of chronic cold exposure, ducklings develop a nonshivering thermogenesis that requires a high energy expenditure. Therefore, energy supply becomes essential to cold-acclimated ducklings, which increase their intake of carbohydrate-rich food. The aim of this work was to investigate the effect of cold acclimation on the activity of the intestinal brush-border Na(+)-D-glucose cotransport, which is the first major step controlling glucose entrance into an organism. Cotransport activity was determined by measuring D-glucose uptake in brush-border membrane vesicles isolated from different parts of the small intestine of thermoneutral control (25 degrees C) or cold-acclimated (4 degrees C) ducklings (Cairina moschata). Two D-glucose transport sites were described in ducklings: a high-affinity/low-capacity site and a low-affinity/high-capacity site. The former was mainly located in the ileum and the latter in the duodenum. These two transport sites were altered differently by cold exposure. Major alterations occur in the ileum where 1) a reduction in the Michaelis-Menten constant and maximal transport rate of the high-affinity site was observed, and 2) the occurrence of low-affinity site activity was noted in cold-acclimated ducklings, although it was not detected in the thermoneutral control group. Cold effect on the high-affinity site could be related to the changes in the ileal brush-border membrane vesicle lipids, whereas cold effect on the low-affinity site could be due, at least in part, to the higher glycosyl content found in this segment. The small intestine appears then able to react to cold exposure by increasing both its mucosa mass in proximal segments and D-glucose uptake capacity in ileum to respond to the higher energy demand induced by thermoregulatory requirements.

Acclimatization↗
PubMed1996

Non-invasive ambulatory blood pressure monitoring: effect on nocturnal sleep of children and adults.

OBJECTIVE: To investigate whether disturbance of sleep by ambulatory blood pressure monitoring determinations might result in altered blood pressure. METHODS: Ninety-seven subjects (29 children and 68 adults) attending an outpatient chronobiology center wore wrist actigraph motion detectors for 48 h (24 h before ambulatory blood pressure monitoring and 24 h during ambulatory blood pressure monitoring). Sleep variables including sleep efficiency, sleep latency, total time in bed, total sleep time, total minutes awake plus number and average duration of awakenings were derived by a dedicated algorithm. RESULTS: Comparison of the sleep variables for the baseline and ambulatory blood pressure monitoring nights revealed no differences in any of the sleep parameters either in the adults or in the children. Small differences between adults and children during the baseline and monitoring nights for some variables were most likely age- and disease-related. CONCLUSION: Non-invasive ambulatory blood pressure monitoring by the SpaceLabs model 90207 device at hourly intervals during night-time sleep does not significantly affect sleep either in children or adults.

Journal Article↗
PubMed1995

Differential recognition of free and covalently bound polyamines by the monoclonal anti-spermine antibody SPM8-2.

The reactivity of an anti-spermine MAb (SPM8-2) toward polyamines either free or bound to a solid surface was investigated using equilibrium dialysis and ELISA methods. When polyamines were covalently linked to hydrophilized microtiter plates using carbodiimide, the MAb SPM8-2 reacted both with spermine and spermidine, with a higher affinity for the latter, but did not show any reactivity towards bound putrescine. In contrast, the MAb SPM8-2 reacted with all three polyamines bound to the microtiter plates with glutaraldehyde, with an affinity in the order: putrescine > spermidine > spermine. Equilibrium dialysis and competitive ELISA tests showed that the MAb SPM8-2 exhibited high affinity for free spermine and 50% and 5% cross-reactivity with free spermidine and putrescine respectively. The affinity of the MAb SPM8-2 for putrescine, spermidine and spermine appears to depend on whether the polyamine is free or bound. The antigenicity of the polyamines differs according to the nature of their link to the solid phase. These observations are discussed in the light of the structural modification produced by covalent binding of the polyamines. It is also concluded that when antibodies are used, due care has to be exercised in choosing the appropriate immunoassay for determining the specificity of antibodies directed against small haptens such as the polyamines.

Animals↗
PubMed1995

Explicit and procedural memory in Parkinson's disease.

One of the aims of cognitive psychology is to breakdown complex tasks into their most basic components. The components of explicit (declarative) and implicit (procedural) memory were thus analyzed in undemented, non-depressed Parkinsonian patients under anti-Parkinsonian treatment, and compared with young and elderly healthy subjects. Three series of experiments were conducted in 61 patients in total. Statistically significant results revealed an impairment of explicit memory (verbal recall of words and drawings) with preserved recall of faces, in Parkinsonians. Implicit memory was also deficient, only in association tests (sound-form; arithmetical alphabet) and maze tests. Braille reading tests and Toronto tower tests did not discriminate between Parkinsonians and elderly subjects. Lastly, analyzing learning and automation revealed a dysfunctioning in Parkinsonian patients. All these data indicate a dysregulation of the cortical-sub-cortical systems, not essentially pre-frontal, and not necessarily dopaminergic. Cognitively, it appears that procedural and implicit memories should be dissociated conceptually.

Adult↗
PubMed1995

Psychological characteristics and the effectiveness of patient-controlled analgesia.

We have evaluated the level of state and trait anxiety, neuroticism, extroversion and coping style as predictors of the effectiveness of patient-controlled analgesia (PCA) in 110 patients undergoing total abdominal hysterectomy. After operation patients were allocated to receive pain control with either PCA or i.m. injections (IMI). Pain was assessed using the short form McGill pain questionnaire at 6, 18 and 24 h after operation, and by recording the amount of analgesic consumed in the first 24 h after surgery. Both state anxiety and coping style were significant predictors of postoperative pain, irrespective of the method of analgesia used. Patients using PCA experienced significantly better pain control than those receiving IMI. However, it was those with high levels of state anxiety who experienced the greatest reduction in pain with PCA. In addition to achieving better pain control, patients who received PCA used significantly less analgesia and were discharged earlier than patients who received IMI.

Adaptation, Psychological↗
PubMed1995

Antibacterial activity of marbofloxacin. A new fluoroquinolone for veterinary use against canine and feline isolates.

Marbofloxacin is a new fluoroquinolone developed exclusively for veterinary use. Minimum inhibitory concentrations of marbofloxacin were assessed for 816 recent isolates associated with canine or feline diseases. Marbofloxacin showed a broad spectrum of activity against gram-negative and gram-positive bacteria. In vitro rates of killing of marbofloxacin and enrofloxacin were compared against strains of Staphylococcus intermedius and Pasteurella multocida, and the results showed no marked difference between the two antibiotics. The duration of bactericidal activity was evaluated ex vivo in the urine of dogs and cats treated with marbofloxacin and lasted from 2 to 5 days after a single administration according to the dosages. Post-antibiotic effect durations were determined with Escherichia coli, Pasteurella multocida, Staphylococcus aureus and Staphylococcus intermedius and were found almost equal to those of enrofloxacin or ciprofloxacin. These results predict a great potential for marbofloxacin in the treatment of a wide range of diseases in dogs and cats.

Animals↗
PubMed1995

[Primary adenoid cystic carcinoma of the skin. Histologic and ultrastructural study of two cases localized in the external auditory canal].

Primary cutaneous adenoid cystic carcinoma is a rare tumor, even if its frequency has often be underestimated, its localization in the external auditory meatus being generally considered separately. The results of the histological and ultrastructural study of two cases of adenoid cystic carcinoma, arising in the external auditory meatus, are presented, confirming the essential morphological similarity of adenoid cystic carcinoma of the skin and salivary glands. In these two cases, the ultrastructural study revealed two types of unique intra luminal inclusions, composed respectively of parallel straight tubular arrays and paracrystalline quadrangular structures, probably corresponding to a peculiar organization of secretion products or cellular debris. The review of 126 published cases of adenoid cystic carcinoma of the skin, including 89 cases developed in the auditory canal, shows that 78% of the cases were located in areas containing numerous apocrine glands, supporting an apocrine gland origin for this tumor. Contrasting with the low (8%) metastatic potential of cutaneous adenoid cystic carcinomas of other locations, adenoid cystic carcinoma of the auditory meatus present a 30% metastatic risk, similar to those or adenoid cystic carcinoma of salivary glands.

Aged↗
PubMed1994

Naturally occurring antibodies reacting with lipoic acid: screening method, characterization and biochemical interest.

The development of a covalent enzyme-linked immunoassay (CELIA) using lipoic acid covalently bound to modified polystyrene microplates has permitted the detection, in the sera of normal BALB/c mice, of natural antibodies reacting with lipoic acid (LA). Hybridomas producing monoclonal anti-LA antibodies were obtained from splenocytes of non-immune BALB/c mice. Two of them, of IgM isotype, recognized LA but failed to react with dihydrolipoic acid (DHLA, the reduced form of LA), suggesting that the integrity of the dithiolane ring was of importance for antibody recognition. They did not give positive reactions with other disulfide linked biological molecules such as oxidized glutathione or cystine. Anti-LA antibodies, coated on polystyrene microplates, were used for the detection of free LA in a competitive assay based on peroxidase-LA conjugate.

Animals↗
PubMed1994

Inhibition of type 5 adenovirus infectivity by periodate oxidation.

Periodate oxidation of purified type 5 Adenovirus (Ad5) led to a mean loss of infectivity of 6.84 logs. There were no significant differences in adsorption and penetration between oxidized and mock-oxidized virus. However, after infection with oxidized virus, no synthesis of viral structural proteins could be detected and a 78.5% inhibition of viral DNA synthesis was observed. Labelling experiments performed by treating oxidized and mock-oxidized virus with tritiated sodium borohydride revealed that the fiber glycoprotein was one of the proteins labelled in oxidized virus whereas no labelled proteins were detected in non oxidized virus. In addition, it was found that one mol of formaldehyde generated during oxidation of sugar residues was bound per 500 base pairs in oxidized virus. One consequence of this in situ generation of formaldehyde is the formation of DNA-protein crosslinks. The DNA so crosslinked showed different patterns of restriction fragments with endonucleases such as Hpa I, Hind III and Kpn I but not with Xho I.

Adenoviruses, Human↗
PubMed1994

The health care needs of ethnic minority groups: are nurses and individuals playing their part?

The UKCC Code of Professional Conduct for nurses, midwives and health visitors stresses the need to have an understanding of the social and cultural determinants of health and illness. There is as yet little evidence of what might constitute good practice in this area and it is difficult to ascertain why this basic philosophy is not translated into action. Indeed, the nursing and midwifery professions' ability to deliver adequate and appropriate health care more generally to Britain's multiracial, multicultural population has been questioned. This literature review presents evidence which strongly suggests that although we are living in a multicultural society patients from minority ethnic groups are additionally disadvantaged because the initiatives by nurses, and others working in the National Health Service, to meet their health care needs are inadequate and often inappropriate.

Delivery of Health Care↗