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Biomedical subjects

A Cooper

Publications and source records attributed to A Cooper.

At least 181 records · Page 10Linked to original sources
PubMed1995

The DvA-1 polyprotein of the parasitic nematode Dictyocaulus viviparus. A small helix-rich lipid-binding protein.

DNA encoding a single unit of the DvA-1 polyprotein of the parasitic nematode Dictyocaulus viviparus was isolated and the polypeptide ("rDvA-1L") expressed in Escherichia coli, to give a protein showing high binding affinity for fatty acids and retinoids. Fluorescent fatty acid probes show substantial changes in emission spectrum in the presence of rDvA-1L, which can be reversed by fatty acids (oleic, palmitic, stearic, arachidonic) and retinoids, but not by tryptophan, squalene, or cholesterol. Moreover, changes in intrinsic fluorescence of retinol or retinoic acid confirm a retinoid binding activity. Fluorescence titration experiments indicate stoichiometric binding to a single protein site per monomer unit with affinities (Kd) in the range 3 x 10(-8) M for 11-((5-dimethylaminonaphthalene-1-sulfonyl)amino)undecanoic acid, and by competition, 5 x 10(-8) M for oleic acid. The extreme blue shift of bound fluorescent fatty acid suggests an unusually low polarity for the protein binding site. The emission spectrum of the single tryptophan of rDvA-1L indicates that it is deeply buried in a nonpolar environment, and its spectrum is unaffected by ligand binding. Far UV circular dichroism of rDvA-1L reveals a high alpha-helix content (53%). Differential scanning calorimetry studies indicate that rDvA-1L is highly stable (T(m) approximately 98 degrees C), refolding efficiently following thermal denaturation. DvA-1 therefore represents an example of a new class of lipid binding protein, and is the first product of a polyprotein with this activity to be described.

Animals↗
PubMed1995

The ABA-1 allergen of the parasitic nematode Ascaris suum: fatty acid and retinoid binding function and structural characterization.

We report here on the structure and function of the ABA-1 allergen protein of the parasitic nematode Ascaris, the first nematode allergen to be characterized in detail. Using the fluorescent fatty acid analog 11-(((5-(dimethylamino)-1-naphthalenyl)sulfonyl)amino)undecanoic acid (DAUDA), it was demonstrated that ABA-1 is a fatty acid binding protein (FABP) with a high affinity for the fluorescent analog (8.8 x 10(-8) M) and for oleic acid in competition experiments (1.3 x 10(-8) M), with a single binding site for ligand per monomer unit. Blue-shifting of fluorescence emission of DAUDA upon binding was unprecedented in degree among FABPs, being equivalent to that occurring in cyclohexane. A similarly blue-shifted spectrum was obtained with a probe in which the fluorophore was bound to the alpha carbon of a fatty acid, indicating that the carboxylate group of bound fatty acids is probably not exposed to solvent. In competition experiments and by observation of changes in their intrinsic fluorescence, retinol and retinoic acid were also found to bind in the fatty acid binding site. Circular dichroism (CD) of the ABA-1 protein revealed a high alpha-helix content (59%) which was consistent with the four-helix structure for the protein predicted from sequence algorithms. Fluorescence measurements showed that the single, highly conserved tryptophan residue is deeply buried in an unusually apolar environment and that this was unaffected by ligand binding. DSC studies of thermal stability indicate that unfolding of the ABA-1 dimer is cooperative and biphasic (Tm approximately 71 and 89 degrees C), suggesting a two-domain thermal unfolding process, again consistent with the predicted structure. Only the folding of the high-temperature domain is reversible on cooling. DSC confirmed the gel filtration analysis, which indicated that ABA-1 forms a dimer. Aside from being the first nematode allergen for which structure or function has been elucidated, ABA-1 provides a highly manipulable model for investigation of the interaction between hydrophobic ligands and alpha-helical proteins.

Allergens↗
PubMed1995

Comparison of Pf1 and Fd gene 5 proteins and their single-stranded DNA complexes by NMR spectroscopy and differential scanning calorimetry.

The Pf1 gene 5 protein forms a large helical nucleoprotein complex (Mr = 3.1 x 10(7)) with single-stranded viral DNA, from which a 32 amino acid sequence rich in alanine, proline, and glutamine residues can be removed from the C-terminus by limited proteolysis. Sharp resonances in the 1H NMR spectrum of the Pf1 nucleoprotein complex indicate that the C-terminal region of the protein subunits enjoys remarkable conformational flexibility in the complex. In contrast, the globular N-terminal domain of the protein subunits is rigidly held and does not contribute to the spectrum. The Fd gene 5 protein lacks this C-terminal flexible domain, and no distinct resonances can be observed in the 1H NMR spectrum when this protein is complexed to single-stranded viral DNA. Differential scanning calorimetry shows that the thermal stability of both the Pf1 and Fd gene 5 protein is increased by 8 degrees C in the complex with DNA, and the transition is highly cooperative. Removal of the C-terminal domain of the Pf1 gene 5 protein subunits has no appreciable effect either on the Tm of the DNA-protein complex or on the cooperative nature of the thermal transition. It is suggested that the C-terminal domain of the Pf1 gene 5 protein acts as a dynamic clamp which kinetically stabilizes the nucleoprotein complex.

Amino Acid Sequence↗
PubMed1995

Mucopolysaccharidosis IVA: structural gene alterations identified by Southern blot analysis and identification of racial differences.

Ninety-six alleles (36 alleles of Japanese and 60 of Caucasian origin) from forty-eight patients with mucopolysaccharidosis IVA were investigated for structural gene alterations using Southern blot analysis. All patients had a previously demonstrated deficiency of N-acetyl-galactosamine-6-sulfate-sulfatase and exhibited a wide spectrum of clinical severity. Initially, using the full-length cDNA as a probe, five of 36 chromosomes from the Japanese patients revealed similar rearrangements with respect to DNA digested with BamHI, SacI, and XhoI. Subsequent analysis using seven genomic fragments, covering the entire gene, enhanced the detection of aberrant fragments produced by the above restriction enzymes. Conversely, the 60 chromosomes of Caucasian origin revealed no evidence of large structural rearrangements when analyzed by these methods. There was a statistically significant difference between the two populations (P < 0.01). A severely affected Japanese patient showed structural rearrangements on both chromosomes by means of BamHI blots. An 8.0-kb fragment and a highly polymorphic 7.0-kb to 11.0-kb fragment present in normal individuals disappeared and two aberrant fragments of 11.5 kb and 12.0 kb were observed. Three other Japanese patients also showed these two aberrant fragments, in addition to the normal fragment pattern, and were thus heterozygous for this rearrangement. Interpretation of Southern blots was difficult because of the complexity of polymorphic bands resulting from variable number of tandem repeat elements. However, by utilizing these aberrant fragments or polymorphic bands, carrier detection was effective, even in families with poorly characterized mutations. Hybridization with probe MG-A (5'-end genomic probe in intron 1) showed a 8.4-kb fragment in BamHI blots of one Japanese and one Caucasian patient; XhoI, SacI, and EcoRI blots were normal. Since this BamHI alteration was also observed in one normal control, it appears to be a rare nonpathological polymorphism.

Alleles↗
PubMed1995

Phylogenetic position of the Chromista plastids based on small subunit rRNA coding regions.

The kingdom Chromista contains eukaryotic organisms with tubular mastigonemes on the leading flagellum of their bi-flagellated stages, and plastids within a chloroplast endoplasmic reticulum (CER). The complex series of events leading to the formation of the CER is hypothesized to have occurred only once. Thus, all organisms with plastid-CER connections are believed to be monophyletic and derived from a single secondary endosymbiotic event. Analyses of sequence data from the 16s rRNA gene from three of the four Chromista pigmented classes indicate that these algae are not monophyletic. The validity of the kingdom Chromista and the number of secondary plastid endosymbioses are questioned.

Base Sequence↗
PubMed1995

How drivers sit in cars.

This paper presents results from a study to measure the separation of the driver's head and shoulder to various internal features of the car. Drivers were filmed whilst driving in general traffic flow, hence were unaware that they were involved in a study. The results show that certain sub-groups of the driver population are likely to be more at risk for certain impact types. Small females are considerably closer to the steering wheel than the rest of the population, and therefore prone to head strikes in frontal impacts. Large males are likely to interact with the cant rail and B-pillar in side impacts.

Accidents, Traffic↗
PubMed1995

The gp15/400 polyprotein antigen of Brugia malayi binds fatty acids and retinoids.

Gp15/400 is a surface-proximal antigen of the filarial nematode Brugia malayi, produced as a large polyprotein precursor comprising an array of polypeptide units of approx. 14.5 kDa. Here we describe a biochemical function for gp15/400. A single 14.5-kDa unit of gp15/400 has been expressed in Escherichia coli, and found to dimerise spontaneously. This protein (designated P-RUNG) has high-affinity fatty acid and retinoid binding activity, suggesting that the parent polypeptide itself has these properties. Fluorescent fatty acid probes show significant enhancement of fluorescence intensity and shifts in emission wavelength in the presence of P-RUNG, which can be reversed by competing non-fluorescent fatty acids (oleic, palmitic, steric, arachidonic), retinoids (retinol and retinoic acid) and oleoyl Coenzyme A, but not by tryptophan, cholesterol, caproic acid, squalene, tocopherol, tocopherol acetate, succinyl CoA, 2-methylbutyric acid and 2-methylvaleric acid. Changes in intrinsic fluorescence of retinol or retinoic acid confirmed the retinoid binding function. The results of fluorescence titration experiments are consistent with stoichiometric binding to a single protein site per monomer unit with affinities (Kd) in the range 2 x 10(-6) M (for the fluorescent probe 11-((5-dansyl)amino)undecanoic acid) and 2 x 10(-7) M (for oleic acid). The extreme blue shift of the fluorescent fatty acid-protein complex suggests an unusually low polarity for the protein binding site. The intrinsic fluorescence of the single tryptophan residue of P-RUNG indicates that it also is deeply buried in a non-polar environment, but is probably not involved in ligand binding. Gp15/400, therefore, represents a new class of lipid binding protein which is possibly restricted to nematodes.

Animals↗
PubMed1995

Closed mitral valvotomy and elective ventilation in the postoperative period: effect of mild hypercarbia on right ventricular function.

OBJECTIVES: It is customary to extubate patients immediately after closed mitral valvotomy. These patients often have deranged respiratory function caused by chronic lung congestion. The left ventricular function may also be subnormal after valvotomy in some patients. Therefore, elective ventilation for some duration in the postoperative period can be beneficial to these patients. This work is an attempt to find whether elective ventilation should be preferred over immediate extubation in these patients. DESIGN: A prospective randomized study. SETTING: The study was performed in a tertiary care hospital, and the patients are referred from the northern states of India. PARTICIPANTS: One hundred patients undergoing elective closed mitral valvotomy were included in the initial part of the study. Ten more patients were studied to evaluate the effect of mild hypercarbia on right ventricular function after closed mitral valvotomy. INTERVENTIONS: One hundred patients were divided into two groups of 50 each. Group 1 consisted of patients in whom the neuromuscular blockade was reversed at the end of surgery with neostigmine and atropine and the trachea was extubated. In group 2, the residual neuromuscular paralysis was not reversed and the patients were electively ventilated in the postoperative period for an average duration of 5 hours and 29 minutes +/- 1 hour and 58 minutes. In all the patients in both the groups, electrocardiogram, direct arterial blood pressure, and oxygen saturation were continuously monitored, and arterial blood gases were measured intermittently throughout the study period. Because the results showed that there was mild hypercarbia, 30 minutes after extubation in group 1, 10 more patients were studied to evaluate the effect of mild hypercarbia on right ventricular function after surgery. Patients were ventilated after surgery (F1O2 = 1) to maintain normocarbia (PaCO238.6 +/- 3.4 mmHg). Mild hypercarbia PaCO251.5 +/- 3.7 mmHg) followed by normocarbia (PaCO2 40 +/- 2.5 mmHg) was induced by adjusting the ventilator rate with a constant tidal volume. Standard hemodynamic measurements were performed at each stage. MEASUREMENTS AND MAIN RESULTS: Although all the patients maintained satisfactory and stable hemodynamics in the postoperative period, the PaCO2 at the end of 30 minutes of extubation was significantly higher in group 1 (48.1 +/- 5.3 mmHg) as compared with group 2 (40.2 +/- 4.3 mmHg, p < 0.001). Mild hypercarbia significantly increased pulmonary vascular resistance (p < 0.01), mean pulmonary arterial pressure (p < 0.001), right ventricular stroke work (p < 0.01), right ventricular systolic pressure (p < 0.01), and right ventricular end-diastolic pressure (p < 0.001). The effect was not totally reversible with CO2 washout as all parameters except right ventricular end-diastolic pressure and pulmonary vascular resistance continued to remain significantly higher when normocarbia was restored. The significant changes in systemic hemodynamics produced by hypercarbia were increases in cardiac index, mean arterial pressure, and pulmonary capillary wedge pressure. CONCLUSIONS: Avoidance of even mild hypercarbia, therefore, appears advisable in the early postoperative period because of potential impedence to right ventricular ejection. Continuous monitoring of end-tidal CO2 and frequent blood gas analyses should be practiced, and elective ventilation should be considered in patients with long-standing disease and pulmonary hypertension.

Adolescent↗
PubMed1995

Nonreamed nailing of tibial diaphyseal fractures in blunt polytrauma patients.

The efficacy of nonreamed nailing as the treatment of choice of unstable blunt tibial diaphyseal fractures was studied. From March 1, 1990, through August 31, 1991, 72 patients with 74 fractures that required fixation were treated. One patient died and six were lost to follow-up, leaving 65 patients with 67 fractures. Follow-up averaged 21 months (range 5-43). Fisher's exact and logistic regression analyses were used to compare grades of open fractures, comminution as classified by Winquist, and dynamic and static nailings. The failure rates of 51 titanium and 16 stainless steel nails were compared. Times to union were compared by the log rank statistic method. The average time to union was 32 weeks with 26 (39%) additional operations required to achieve union; 13 dynamizations (12 successful), 12 exchange nailings (11 successful), and one plate and bone graft. The rate of reconstructive procedures to achieve union was a more sensitive indicator of difficulties achieving union than was time to union. Reoperation rates were 33% for closed or grade I and II fractures compared with 46% for grade III fractures (NS). Among closed grade I and II static versus dynamic nailing, times to union were 36 versus 25 weeks (p < 0.01), and the reoperation rates were 44% versus 13% (p < 0.04). Winquist I and II fractures required a 24% reoperation rate versus 53% for grade III and IV and segmental fractures (p < 0.01). Static locked fractures required a 48% reoperation rate versus 12% for dynamic locked fractures (p < 0.01). A logistic regression analysis demonstrated that locking mode was the most important factor in determining reoperation rates. Fifteen additional reoperations for infection, broken or painful implants, or to remodel bones that united with an incomplete circumference of cortex were performed. With an additional 12 elective nail removals, the total reoperations numbered 53 (79%). Titanium alloy nails had a 2% failure rate versus 25% for stainless steel nails (p < 0.01). Two of 28 (7%) grade III fractures became infected. All fractures united within 10 degrees of normal alignment and 1 cm of length. Nine (13%) united with an incomplete cortical circumference, refractory to dynamization and full weight bearing. Thirteen of the 58 (22%) fractures available for an evaluation of ankle motion were symptomatic, with < 10 degrees of dorsiflexion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1995

Assessing the work of medical audit advisory groups in promoting audit in general practice.

Objectives--To determine the role of medical audit advisory groups in audit activities in general practice. Design--Postal questionnaire survey. Subjects--All 104 advisory groups in England and Wales in 1994. Main measures--Monitoring audit: the methods used to classify audits, the methods used by the advisory group to collect data on audits from general practices, the proportion of practices undertaking audit. Directing and coordinating audits: topics and number of practices participating in multipractice audits. Results--The response rate was 86-5%. In 1993-4, 54% of the advisory groups used the Oxfordshire or Kirklees methods for classifying audits, or modifications of them. 99% of the advisory groups collected data on audit activities at least once between 1991-2 and 1993-4. Visits, questionnaires, and other methods were used to collect information from all or samples of practices in each of the advisory group's areas. Some advisory groups used different methods in different years. In 1991-2, 57% of all practices participated in some audit, in 1992-3, 78%, and in 1993-4, 86%. 428 multipractice audits were identified. The most popular topic was diabetes. Conclusions--Advisory groups have been active in monitoring audit in general practice. However, the methods used to classify and collect information about audits in general practices varied widely. The number of practices undertaking audit increased between 1991-2 and 1993 1. The large number of multipractice audits supports the view that the advisory groups have directed and coordinated audit activities. This example of a national audit programme for general practice may be helpful in other countries in which the introduction of quality assurance is being considered.

England↗
PubMed1995

Effect of antihypertensive treatment on small arteries of patients with previously untreated essential hypertension.

In a double-blind randomized trial, the effects of treatment with an angiotensin-converting enzyme (ACE) inhibitor (perindopril) and a beta-blocker (atenolol) on small artery structure were compared in previously untreated essential hypertensive patients. Subjects (diastolic blood pressure > or = 100 and < or = 120 mm Hg) were randomly assigned to treatment for 12 months with either perindopril (n = 13, 4 to 8 mg/d) or atenolol (n = 12, 50 to 100 mg/d); the dosage was adjusted upward and in some cases combined (n = 5, perindopril; n = 2, atenolol) with thiazide diuretic to achieve target blood pressure (diastolic blood pressure below 90 mm Hg). Before and at the end of treatment, gluteal biopsies were taken under local anesthetic; from these biopsies, two small arteries were dissected and mounted on a myograph for morphometry. The reduction in blood pressure with atenolol (drop in mean blood pressure 28.4 +/- 1.8 mm Hg) was greater than with perindopril (20.6 +/- 1.8 mm Hg, P < .05). Perindopril treatment caused an increase in small artery diameter (231 +/- 14 to 274 +/- 13 microns, P < .05) and a reduction in the ratio of media thickness to lumen diameter (7.94 +/- 0.65% to 5.96 +/- 0.42%, P < .05), whereas atenolol had no effect (246 +/- 14 to 231 +/- 13 microns and 7.14 +/- 0.47% to 6.79 +/- 0.45%, respectively). The change in small artery morphology caused by perindopril was not accompanied by any change in media cross-sectional area, suggesting that the change was due to "remodeling."(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The surgeon and emergency medical services for children.

A central focus of emergency medical services for children is the critically injured child, whose potential for recovery is great. Yet trauma remains the leading cause of mortality and morbidity among American children 1-14 years of age. Much unnecessary death and disability can be avoided through aggressive professional and public education in pediatric advanced life support and injury prevention. As the primary-care physician of the critically injured child, the surgeon plays a leading role in ensuring that trauma and emergency medical services systems are optimally prepared to meet the dual challenges of providing optimal pediatric trauma care and obviating the need for such treatment through all means possible.

Child↗
PubMed1995

Thoracic injuries.

Thoracic injury is the second leading cause of death in pediatric trauma, second only to head injury in lethal potential. With the exception of lung contusion, serious injuries to vital thoracic structures are associated with mortality rates in excess of 50%. With blunt chest trauma, approximately 15% of the deaths result directly from intrathoracic injury, but with penetrating chest trauma, nearly 100% of the deaths result from intrathoracic injury. Facility with management of thoracic injuries is therefore vital to optimal outcome in childhood trauma.

Cause of Death↗
PubMed1995

Menopause: refining benefits and risks of hormone replacement therapy.

In terms of our understanding of menopause and hormone replacement therapy, 1993-1994 did not see any seminal or definitive publications. However, the data that were published have helped refine our understanding of the benefits and risks of hormone replacement therapy. This article presents further evidence for the protective effects of hormone replacement therapy in preventing osteoporosis and arterial disease, including direct gonadal hormone effects upon the vessel wall; discusses changes in attitudes to progestogen additions, withdrawal bleeding and endometrial status; reviews controversies over the relationship between hormone replacement therapy and breast cancer risk, and briefly mentions a new device for delivery of non-oral oestradiol.

Breast Neoplasms↗
PubMed1995

Mucopolysaccharidosis IVA: identification of a common missense mutation I113F in the N-Acetylgalactosamine-6-sulfate sulfatase gene.

Mucopolysaccharidosis IVA is an autosomal recessive lysosomal storage disorder caused by a deficiency of N-acetylgalactosamine-6-sulfate sulfatase. The recent isolation and characterization of cDNA and genomic sequences encoding GALNS has facilitated identification of the molecular lesions that cause MPS IVA. We identified a common missense mutation among Caucasian MPS IVA patients. The mutation was originally detected by SSCP, and successive sequencing revealed an A-->T transversion at nt 393. This substitution altered the isoleucine at position 113 to phenylalanine (I113F) in the 622 amino acid GALNS protein and was associated with a severe phenotype in a homozygote. Compound heterozygotes with one I113F-allele mutation have a wide range of clinical phenotypes. Transfection experiments in GALNS-deficient fibroblasts revealed that the mutation drastically reduces the enzyme activity of GALNS. Allele-specific oligonucleotide or SSCP analysis indicated that this mutation accounted for 22.5% (9/40) of unrelated MPS IVA chromosomes from 23 Caucasian patients, including 6 consanguineous cases. Of interest, the I1e 113-->Phe substitution occurred in only Caucasian MPS IVA patients and in none of the GALNS alleles of 20 Japanese patients. These findings identify a frequent missense mutation among MPS IVA patients of Caucasian ancestry, that results in severe MPS IVA when homoallelic, and will facilitate molecular diagnosis of most such patients and identification of heterozygous carriers. In addition to this common mutation, 10 different point mutations and 2 small deletions were detected, suggesting allelic heterogeneity in GALNS gene.

Base Sequence↗