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Biomedical subjects

A Rees

Publications and source records attributed to A Rees.

At least 55 records · Page 3Linked to original sources
PubMed1999

Effects of humanization by variable domain resurfacing on the antiviral activity of a single-chain antibody against respiratory syncytial virus.

HNK20 is a mouse monoclonal IgA that binds to the F glycoprotein of respiratory syncytial virus (RSV) and neutralizes the virus, both in vitro and in vivo. The single-chain antibody fragment (scFv) derived from HNK20 is equally active and has allowed us to assess rapidly the effect of mutations on affinity and antiviral activity. Humanization by variable domain resurfacing requires that surface residues not normally found in a human Fv be mutated to the expected human amino acid, thereby eliminating potentially immunogenic sites. We describe the construction and characterization of two humanized scFvs, hu7 and hu10, bearing 7 and 10 mutations, respectively. Both molecules show unaltered binding affinities to the RSV antigen (purified F protein) as determined by ELISA and surface plasmon resonance measurements of binding kinetics (Ka approximately 1x10(9) M-1). A competition ELISA using captured whole virus confirmed that the binding affinities of the parental scFv and also of hu7 and hu10 scFvs were identical. However, when compared with the original scFv, hu10 scFv was shown to have significantly decreased antiviral activity both in vitro and in a mouse model. Our observations suggest that binding of the scFv to the viral antigen is not sufficient for neutralization. We speculate that neutralization may involve the inhibition or induction of conformational changes in the bound antigen, thereby interfering with the F protein-mediated fusion of virus and cell membranes in the initial steps of infection.

Algorithms↗
PubMed1999

Diabetic dyslipidaemia and coronary heart disease: new perspectives.

Atherosclerotic macrovascular disease is the leading cause of both morbidity and mortality in non-insulin dependent diabetes mellitus. Endothelial dysfunction is a key, early and potentially reversible event in pathogenesis of atherosclerosis. Its occurrence in non-insulin dependent diabetes mellitus is well supported by both in-vitro and in-vivo studies. Non-insulin dependent diabetes mellitus results in diverse abnormalities of lipid and lipoprotein metabolism, in particular hypertriglyceridaemia, low levels of high density lipoprotein and abnormalities of post-prandial lipaemia. A variety of studies demonstrate the presence of enhanced oxidative stress in non-insulin dependent diabetes mellitus, with recent data implying an association between oxidative stress, post-prandial lipaemia and endothelial dysfunction in non-diabetic subjects. In this article based on in-vitro and human studies, we develop the hypothesis that endothelial dysfunction in non-insulin dependent diabetes mellitus is the consequence of the diabetic dyslipidaemia, in particular post-prandial lipaemia, and of oxidative stress on the action of nitric oxide. The practical applications of this theory provide potential therapeutic options which may reduce the risk of vascular disease in non-insulin dependent diabetes mellitus.

Coronary Disease↗
PubMed1998

Sensitivity to dynamic auditory and visual stimuli predicts nonword reading ability in both dyslexic and normal readers.

BACKGROUND: Developmental dyslexia is a specific disorder of reading and spelling that affects 3-9% of school-age children and adults. Contrary to the view that it results solely from deficits in processes specific to linguistic analysis, current research has shown that deficits in more basic auditory or visual skills may contribute to the reading difficulties of dyslexic individuals. These might also have a crucial role in the development of normal reading skills. Evidence for visual deficits in dyslexia is usually found only with dynamic and not static stimuli, implicating the magnocellular pathway or dorsal visual stream as the cellular locus responsible. Studies of such a dissociation between the processing of dynamic and static auditory stimuli have not been reported previously. RESULTS: We show that dyslexic individuals are less sensitive both to particular rates of auditory frequency modulation (2 Hz and 40 Hz but not 240 Hz) and to dynamic visual-motion stimuli. There were high correlations, for both dyslexic and normal readers, between their sensitivity to the dynamic auditory and visual stimuli. Nonword reading, a measure of phonological awareness believed crucial to reading development, was also found to be related to these sensory measures. CONCLUSIONS: These results further implicate neuronal mechanisms that are specialised for detecting stimulus timing and change as being dysfunctional in many dyslexic individuals. The dissociation observed in the performance of dyslexic individuals on different auditory tasks suggests a sub-modality division similar to that already described in the visual system. These dynamic tests may provide a non-linguistic means of identifying children at risk of reading failure.

Acoustic Stimulation↗
PubMed1998

Cardiopulmonary effects of 7.2% saline solution compared with gelatin infusion in the early postoperative period after coronary artery bypass grafting.

OBJECTIVE: We report a clinical study on the use of 7.2%, 2400 mOsm/L, hypertonic saline solution compared with gelatin in early postoperative period after coronary artery bypass surgery. METHODS: Two groups (n = 10 each) received 5 ml/kg of either saline solution or gelatin over 1 hour. Cardiac index, central venous pressure, pulmonary capillary wedge pressure, systemic and pulmonary vascular resistance indices, arterial oxygen tension, plasma osmolarity, electrolytes, and urinary output were recorded before starting the infusion and subsequently at 10, 30, 60, 90, 120, 240 and 600 minutes. Plasma creatinine, urea, electrolytes, urinary volume, and sodium excretion were measured at 12 and 24 hours. RESULTS: There were no significant demographic or operative difference between the groups. Patients receiving saline solution had a larger diuresis at 12 (p = 0.0008) and 24 hours (p = 0.002), with less positive balance at 12 hours (p = 0.0008). The group receiving saline solution had better cardiorespiratory recovery with shorter extubation time (p = 0.033), and earlier increase in cardiac index with a positive correlation between plasma sodium content and cardiac index. Maximum increase in cardiac index (+31%) occurred at 60 minutes (p = 0.025) associated with 8% increase in plasma sodium content (r = 0.51, p = 0.01), without a concomitant rise in pulmonary capillary wedge pressure. The group receiving gelatin had a linear increase in cardiac index with increasing pulmonary capillary wedge pressure, reaching +16% from baseline by 90 minutes. Compared with the gelatin-treated group, patients receiving saline solution had unchanged systemic vascular resistance index but a significantly lower pulmonary vascular resistance index with a negative correlation to plasma sodium content. There was no difference in levels of urea and creatinine. No side-effect attributable to the use of saline solution was observed.

Coronary Artery Bypass↗
PubMed1998

The oestrogen receptor regulates NFkappaB and AP-1 activity in a cell-specific manner.

Oestrogens regulate the expression of genes both positively and negatively in a range of cell types. These effects are mediated via the oestrogen receptor (ER) and involve direct interactions between the ER and DNA response elements, as well as interactions between the ER and other nuclear proteins. We have examined the potential of the ERalpha to regulate the expression of reporter genes under the control of oestrogen response elements (EREs), NFkappaB response elements (NREs) or AP-1/TPA response elements (TREs) in HeLa cells and in human embryonic kidney (HEK-293) cells. Transiently transfected ERalpha was able to activate expression of beta-galactosidase under the control of EREs in an oestradiol (E2)-dependent manner in both HeLa and HEK-293 cells. The ERalpha was able to repress by 80% the TNF-mediated expression of beta-galactosidase under the control of NREs in an E2-dependent manner in HeLa cells but not in HEK-293 cells. ERalpha/E2 also induced a two-fold potentiation of TPA-mediated expression of beta-galactosidase under the control of TREs in HeLa cells but not in HEK-293 cells. These results suggest that the ERalpha is capable of regulating gene expression in a cell-specific manner. We further investigated the mechanisms by which the ERalpha regulates gene expression in these systems by co-expressing the ERalpha and the reporter gene constructs with known cofactors of the ERalpha. We have shown that expression of steroid receptor coactivator-1 alpha (SRC-1alpha) and receptor interacting protein-140 (RIP-140) have no effect on the capacity of the ERalpha to modulate NFkappaB reporter gene activity in HeLa cells. Furthermore, the expression of SRC-1alpha or RIP-140 does not enable the ERalpha to repress NFkappaB or to potentiate an AP-1 response in HEK-293 cells. This suggests that factors other than SRC-1alpha or RIP-140 are responsible for the cell-specific effects seen with ERalpha.

Dexamethasone↗
PubMed1998

Right parietal cortex is involved in the perception of sound movement in humans.

Changes in the delay (phase) and amplitude of sound at the ears are cues for the analysis of sound movement. The detection of these cues depends on the convergence of the inputs to each ear, a process that first occurs in the brainstem. The conscious perception of these cues is likely to involve higher centers. Using novel stimuli that produce different perceptions of movement in the presence of identical phase and amplitude modulation components, we have demonstrated human brain areas that are active specifically during the perception of sound movement. Both functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) demonstrated the involvement of the right parietal cortex in sound movement perception with these stimuli.

Acoustic Stimulation↗
PubMed1997

Cleavage specificity of a proteolytic antibody light chain and effects of the heavy chain variable domain.

The recombinant light chain (L chain) of an antibody raised by immunization with vasoactive intestinal polypeptide (VIP) cleaved this peptide on the C-terminal side of basic residues. The major sites of cleavage in VIP were two adjacent peptide bonds, Lys20-Lys21 and Lys21-Tyr22. Lower levels of cleavage were evident at Arg14-Lys15 and Lys15-Gln16. Hydrolysis of radiolabeled VIP by the L chain was inhibited by two serine protease inhibitors, diisopropylfluorophosphate and aprotinin, but not by soybean or lima bean trypsin inhibitors or inhibitors of other classes of proteases. To probe the role of the VH domain, single chain Fv constructs composed of the VL domain of the anti-VIP L chain linked via a 14-residue peptide to its natural VH domain partner or an irrelevant anti-lysozyme VH domain (hybrid Fv) were prepared. The anti-VIP Fv hydrolyzed VIP with Ks 21.4-fold lower than the L chain and 250-fold lower than the hybrid Fv, suggesting increased affinity for the substrate ground state due to the anti-VIP VH domain. The kinetic efficiency (kcat/Ks) of the anti-VIP Fv was 6.6-fold greater compared to the L chain and 29.4-fold greater compared to the hybrid Fv. Peptide-MCA substrates unrelated in sequence to VIP were hydrolyzed by the anti-VIP Fv and L chain at equivalent rates. These observations lead to a model of catalysis by the anti-VIP Fv in which the essential catalytic residues are located in the VL domain and additional residues from the VH domain are involved in high affinity binding of the substrate.

Amino Acid Sequence↗
PubMed1997

Alpha4 integrin binding interfaces on VCAM-1 and MAdCAM-1. Integrin binding footprints identify accessory binding sites that play a role in integrin specificity.

Integrins are a family of heterodimeric adhesion receptors that mediate cellular interactions with a range of matrix components and cell surface proteins. Vascular cell adhesion molecule-1 (VCAM-1) is an endothelial cell ligand for two leukocyte integrins (alpha4beta1 and alpha4beta7). A related CAM, mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is recognized by alpha4beta7 but is a poor ligand for alpha4beta1. Previous studies have revealed that all alpha4 integrin-ligand interactions are dependent on a key acidic ligand motif centered on the CAM domain 1 C-D loop region. By generating VCAM-1/MAdCAM-1 chimeras and testing recombinant proteins in cell adhesion assays we have found that alpha4beta1 binds to the MAdCAM-1 adhesion motif when present in VCAM-1, but not when the VCAM-1 motif was present in MAdCAM-1, suggesting that this region does not contain all of the information necessary to determine integrin binding specificity. To characterize integrin-CAM specificity further we measured alpha4beta1 and alpha4beta7 binding to a comprehensive set of mutant VCAM-1 constructs containing amino acid substitutions within the predicted integrin adhesion face. These data revealed the presence of key "regulatory residues" adjacent to integrin contact sites and an important difference in the "footprint" of alpha4beta1 and alpha4beta7 that was associated with an accessory binding site located in VCAM-1 Ig domain 2. The analogous region in MAdCAM-1 is markedly different in size and sequence and when mutated abolishes integrin binding activity.

Amino Acid Sequence↗
PubMed1997

Covariance in the measurement of depression/anxiety and three Cluster C personality disorders (avoidant, dependent, obsessive-compulsive).

One hundred and eight-four clients referred to a research outpatient psychological clinic, and meeting the acceptance criterion of 16 or more on the BDI at screening, were diagnosed as either-depressed and/or anxious using both Present State Examination and the Diagnostic and Statistical Manual of Mental State Disorders criteria. Clients were assessed for the presence of Cluster C personality disorders using the Personality Disorder Examination of Loranger et al. (1985). Twenty-two per cent made diagnosis of avoidant, dependent or obsessive-compulsive personality disorder. Significant correlation was found between screening/intake depression index scores and total scores on the three Cluster C personality disorders, although little correlation was found between diagnostic criteria for affective and personality disorders. Some association was shown between the clinical components of personality disorder traits in the anxious-fearful group and current anxiety symptoms, although not as clearly as expected.

Adult↗
PubMed1997

Spatial and temporal auditory processing deficits following right hemisphere infarction. A psychophysical study.

Higher auditory function in a patient was investigated following a right hemisphere infarction between the middle and posterior cerebral artery territories involving the insula. The patient complained of lack of musical appreciation and a battery of tests confirmed a dissociated receptive musical deficit in the presence of normal appreciation of environmental sounds and speech. The ability to detect continuous changes in sound frequency in the form of sinusoidal frequency modulation was preserved. There was, however, a deficit in the analysis of rapid temporal sequences of notes which could underlie his musical deficit. This case provides further evidence for the existence of amusia as a distinct form of auditory agnosia, but does not support the hypothesis that bilateral lesions are required to produce such a deficit. Unexpectedly, the patient was also found to have a deficit in the perception of apparent sound-source movement. We suggest that this deficit is analogous to the visual phenomenon of akinetopsia, and is in accord with PET work suggesting involvement of areas outside primary auditory cortex in sound movement perception. A possible common deficit in auditory temporal and spatial 'scene analysis' is discussed.

Acoustic Stimulation↗
PubMed1997

Sound movement detection deficit due to a brainstem lesion.

Auditory psychophysical testing was carried out on a patient with a central pontine lesion involving the trapezoid body, who presented with a deficit in sound localisation and sound movement detection. A deficit in the analysis of time and intensity differences between the ears was found, which would explain the deficit in detection of sound movement. The impaired detection of sound movement, due to a lesion interfering with convergence of auditory information at the superior olive, suggests this structure to be critical for human sound movement analysis.

Audiometry, Pure-Tone↗
PubMed1997

Regularity of firing of neurons in the inferior colliculus.

The spike discharge regularity of 254 tonically firing units in the inferior colliculus (IC) of the anesthetized guinea pig was studied in response to tones presented at best frequency (BF) to the ear contralateral to the recorded IC. Regularity of firing was measured by calculating the coefficient of variation (CV) as a function of time over the course of a unit's response. Two hundred and fifteen units (56 under urethan and 159 under chloralose anesthesia) in the central nucleus of the IC (CNIC) were studied in detail. In response to tones at 15-25 dB above threshold, 80% of units in the urethan sample fired regularly (CV < 0.5) during their sustained response, and 46% were highly regular (CV < or = 0.35). For chloralose the values were 68% and 23%, respectively. Units recorded under urethan were significantly more regular than those recorded under chloralose. For units in the sample with a measurable onset CV, 63% were regular and 44% highly regular under urethan, and 73% were regular and 54% highly regular under chloralose. The units' peristimulus time histogram (PSTH) patterns were classified into subdivisions of four categories: choppers [9%: chop-sustained (Cs), chop-onset (Co)]; pausers [42%: pauser-chop-sustained (P/Cs), pauser-chop-onset (P/Co), pauser-no-chop]; ON-sustained (43%: primary-type, L-type, h-type); and sustained (6%). The presence of chopping was a reliable predictor of regularity: Cs and P/Cs units were highly regular throughout their response, whereas Co and P/Co units were highly regular at onset and became less regular. Some units in the other PSTH categories were highly regular despite the absence of chopping, and units with virtually identical PSTHs showed very different sustained CVs. Regularity was measured as a function of firing rate in 71 units. In 23%, regularity remained constant when firing rate changed with stimulus level. Forty-six percent fired more regularly as firing rate increased, 8% fired less regularly, and 23% of units showed no consistent relationship between CV and firing rate. Regularity did not correlate with the neurons' frequency response areas or BFs. Regular firing was also found in a smaller sample of units recorded in cortices surrounding the CNIC. We conclude that regular firing is a characteristic feature of most neurons in the IC. Regularity is a specific feature correlated with four PSTH types (Cs, Co, P/Cs, and P/Co). Other PSTH types may or may not exhibit regularity.

Animals↗
PubMed1997

Reduced frequency of severe hypoglycemia and coma in well-controlled IDDM patients treated with insulin lispro. The Benelux-UK Insulin Lispro Study Group.

OBJECTIVE: Several studies have suggested that use of the short-acting insulin analog, insulin lispro, in multiple injection therapy may reduce the risk of hypoglycemia in comparison with regular insulin. This effect might be more pronounced in well-controlled patients, since intensive treatment of IDDM increases the rate of severe hypoglycemic events. This study evaluated the effects of insulin lispro on glycemic control and hypoglycemia rates in well-controlled IDDM patients. RESEARCH DESIGN AND METHODS: This was an open, randomized, 6-month crossover study of 199 IDDM patients. Glycemic control was evaluated by HbA1c, home blood glucose measurements, and rate and timing of hypoglycemic events. At the end of the study, patients completed an evaluation form regarding therapy-related quality of life. RESULTS: HbA1c remained constant at approximately 7.3% throughout the study. Meal-related glucose excursions were significantly lower with insulin lispro compared with regular insulin (mean -0.8 +/- 1.7 vs. 1.1 +/- 1.6 mmol/l, P < 0.001), as was the within-day variability (M value 27.7 +/- 19.7 vs. 30.2 +/- 23.1, P = 0.007). The incidence of severe hypoglycemic events (58 vs. 36, P = 0.037) including coma (16 vs. 3, P = 0.004) was significantly lower with insulin lispro than with regular insulin. Patients felt that insulin lispro increased flexibility and freedom of lifestyle. CONCLUSIONS: In well-controlled IDDM patients, insulin lispro is associated with a lower risk of severe hypoglycemia and coma.

Adult↗