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Biomedical subjects

A Thomas

Publications and source records attributed to A Thomas.

At least 361 records · Page 20Linked to original sources
PubMed1994

Endometrial thickness: a predictor of implantation in ovum recipients?

In a retrospective study, the relationship between endometrial thickness and pregnancy rate has been studied in 59 ovum recipient women. Transvaginal ultrasound assessment of endometrial thickness was performed immediately prior to ovum transfer: 19 pregnant recipients had a mean endometrial thickness of 10.24 mm +/- 2.63 SD, 40 nonpregnant recipients had an endometrial thickness of 8.62 mm +/- 3.49 SD (t = 1.805, P = 0.0382). Only two pregnancies occurred in 15 recipients with an endometrial thickness < 7.5 mm, and none when the endometrial thickness was < 5 mm. Our results indicate that endometrial thickness is related to the functional receptivity of the endometrium.

Adult↗
PubMed1994

Engineering of protein epitopes: a single deletion in a snake toxin generates full binding capacity to a previously unrecognized antibody.

Structural features associated with the ability of a monoclonal antibody (mAb) to discriminate between protein variants are identified and engineered. The variants are the curaremimetic toxin alpha from Naja nigricollis and erabutoxin a or b from Laticauda semifasciata, which differ from each other by 16 substitutions and one insertion. The neutralizing mAb M alpha 1 recognizes with high affinity a topographical epitope on the surface of toxin alpha, but fails to recognize the erabutoxins although they possess most of the residues forming the presumed epitope. Examinations of the toxin alpha and erabutoxin 3-D structures and molecular dynamics simulations reveal several differences between the variants. In particular, the region involving the beta-turn 17-24 is organized differently. Analysis of the differences found in this region suggest that the insertion (or deletion) at position 18 of the variant amino acid sequences is particularly important in determining the differential cross-reactivity. To test this proposal, residue 18 was deleted in one erabutoxin using site-directed mutagenesis, and the biological properties of the resulting mutant were examined. We found that full antigenicity was restored in the previously unrecognized variant. The implications of this finding are discussed.

Amino Acid Sequence↗
PubMed1994

The detection of Vero cytotoxin-producing Escherichia coli and Shigella dysenteriae type 1 in faecal specimens using polymerase chain reaction gene amplification.

Fifty consecutive faecal specimens received by the LEP were examined for the presence of Vero cytotoxin (VT) genes by polymerase chain reaction (PCR) gene amplification. Nineteen were positive by PCR and from 16 of these, VT positive Escherichia coli O157 were isolated. The remaining three samples were positive for VT genes by PCR but VTEC were not isolated. In a preliminary experiment, Shigella dysenteriae type 1 was isolated from a case of bloody diarrhoea following a positive amplification result.

Bacterial Toxins↗
PubMed1994

An epidemiological study of headache among the Monks of Athos (Greece).

The Monks of Athos in Greece constitute a particular group with unusual sleep schedule and specific diet. In order to study the frequency of headache among them, a special questionnaire was designed. Four hundred forty-nine monks below the age of 50 were approached, 39 of whom suffered from frequent (more than one episode per month, in the last 6 months) headaches (8.68%). The prevalence of migraine was 1.78% (0.66% with aura and 1.11% without) and of tension-type headache 3.34% (1.33% chronic and 2% episodic). Furthermore, 1.87% of monks suffered from mixed headaches (tension-type and migraine attacks as well). Cluster headache was not traced.

Adult↗
PubMed1994

Sudden death in recipients of first-generation implantable cardioverter defibrillators: analysis of terminal events. Participating investigators.

Clinical factors and terminal events associated with sudden death in 51 patients were analyzed from among a multicenter experience of 864 recipients of first generation automatic implantable cardioverter defibrillator (AICD) devices (single zone, committed, monophasic pulse with > or = 1 epicardial patch electrode) during the period May 1982-February 1988. For these 51 patients, mean age was 58 years and atherosclerotic heart disease was present in 84%, with a history of ventricular fibrillation (VF) in 61%, and inducible sustained ventricular tachycardia (VT) in 84%; mean left ventricular ejection fraction was 0.26. Nearly 80% experienced one or more appropriate AICD shocks during the median 9 month (range 0-46 months) period prior to death. Of 30 monitored deaths, the first documented terminal rhythm was VF in 12 (40%), VT in 8 (27%), and asystole or electromechanical dissociation in the remaining 10 (33%). Shocks were documented during terminal events in 21 (66%) of 32 witnessed cases of sudden death with activated devices. The proportion of monitored or witnessed sudden deaths that were known or presumed to be tachyarrhythmic (based on terminal VT, VF, or shocks) ranged from 69% (11/16 cases with activated/nondepleted devices and a defibrillation threshold [DFT] < or = 20 J) to 81% (29/36 cases on intention-to-treat basis). Of 27 patients with known or presumed sudden tachyarrhythmic death, the AICD had been deactivated prior to death in 4 (15%); activated, but depleted in 4 (15%); activated/nondepleted, but with DFT of 25 J in 4 (15%); and activated/nondepleted, but without DFT testing in 4 (15%). The remaining 11 (41%) known or presumed sudden tachyarrhythmic deaths occurred in patients with activated/nondepleted devices and DFT < or = 20 J; however, definite or suspected contributory factors (e.g., hematoma under epicardial patch, generator component failure, or drug-induced DFT rise) could be identified in 6 (55%) of 11 cases. Thus, in this first-generation AICD experience: 1) most sudden deaths occurred on the basis of a known or presumed tachyarrhythmia; and 2) an understanding of apparent "failure" of ICD therapy could often be gained through an integrated analysis of associated clinical factors and management practices, as well as device "hardware" function. These observations are likely to remain relevant, even with respect to newer generation ICDs.

Aged↗
PubMed1994

Hand dystonia secondary to cervical demyelinating lesion.

Dystonia is generally considered a disease of basal ganglia. We report two patients with definite MS who acutely developed hand dystonia and athetoid movements. In both patients: 1) dystonia was electrophysiologically demonstrated by lack of reciprocal inhibition between antagonistic forearm muscles; 2) SEP from median nerve stimulation showed delayed cervical N13 and absent frontal and parietal components; 3) the long latency response after stimulation of median nerve of the affected hand was absent or delayed; 4) MRI showed lesions in the posterolateral cervical spine but no involvement of basal ganglia and thalami. We think that, in these cases, dystonia and athetoid movements could be ascribed respectively to the involvement of descending pathways regulating reciprocal inhibition of motoneurons and to the involvement of large diameter afferents due to the demyelinating lesion at the cervical level.

Adult↗
PubMed1994

An in vitro investigation into the cutting ability of ultrasonic K files.

Endosonic files vary in their oscillation when operated in air with the greatest displacement at the unconstrained tip. It was the aim of this study to investigate how files of different lengths and sizes varied in their ability to cut dentine. Single rooted teeth were sectioned to produce 1 mm dentine discs. These were positioned on a plastic block connected to a load transducer. Endosonic K-files (#15 to 25) were used to cut the disc for 10 s using operator assisted movement. The files contacted the disc at the following points along their length; apical (3 mm from tip), middle (8 mm from tip) and coronal (13 mm from tip) under applied loads of 30 and 50 g. The depth of cut produced by each file was measured using light microscopy. The #15 and #25 were similar in their pattern of dentine removal. The #20 file produced a large variation in its cutting ability and was also susceptible to fracture. The tip of the files was prone to constraint at higher loading with the thicker part of the file producing more cutting. It was concluded that the pattern of dentine removal of endosonic files was affected by the amount of load applied. The displacement amplitudes of endosonic files in air would not appear to be a good indicator of file cutting ability.

Analysis of Variance↗
PubMed1994

Hybridization of strains of Escherichia coli O157 with probes derived from the eaeA gene of enteropathogenic E. coli and the eaeA homolog from a Vero cytotoxin-producing strain of E. coli O157.

A total of 375 Escherichia coli O157 strains were tested by colony hybridization with the eae probe from the central portion of the eaeA gene of the classical enteropathogenic E. coli strain E2348/69. They were also tested with a probe, eaeO157, from the C-terminal end of the eae gene homolog from a Vero cytotoxin (VT)-producing strain of E. coli (VTEC) of serotype O157:H7. Both probes hybridized with all 246 O157:H7 or H- VTEC strains tested. The majority were from human infections, and the remainder were from cattle. A further 10 strains (H7 or H-) hybridized with both eae and eaeO157 sequences but not with VT probes. They resembled O157 VTEC and were probably naturally occurring derivatives that had lost VT genes. The remaining 119 strains of O157 were from human, animal, and food sources and belonged to 16 H types other than H7 or were H-. They were VT negative and differed in their properties from O157 VTEC: generally they fermented sorbitol in 1 day, produced beta-glucuronidase, and could not be phage typed by the scheme for O157 VTEC. The eae probe but not the eaeO157 sequence hybridized with 18 H8 or H39 strains, predominantly from human diarrhea. The remaining 101 VT-negative strains hybridized with neither probe. However, 16 strains of O157:H45 hybridized with a probe for diffusely adherent E. coli and attached to HEp-2 cells in a diffuse pattern. Serogroup O157 comprises strains with heterogeneous properties. The eaeO157 probe is a valuable addition to the VT probes used to differentiate O157 strains.

Animals↗
PubMed1994

Paralympics--Barcelona 1992.

The British Team at the 9th Paralympic Games in September 1992 in Barcelona comprised 151 men and 54 women athletes in a total of 15 sports. They were supported by a staff of 86 including a 12-strong medical team. The athletes were selected from the National Championships of the five disability organizations: British Wheelchair Sports Federation; British Blind Sport; Cerebral Palsy Sport; British Amputee Sports Association; and the British Les Autres Sports Association. This article outlines the organization and experience of the medical support team. The injury/illness profile was similar to those in able bodied sport. The team went on to achieve 40 gold, 47 silver and 41 bronze medals, maintaining third place on the medal table as achieved in Seoul in 1988.

Amputees↗
PubMed1994

The consequences of malaria infection in pregnant women and their infants.

Preliminary results are presented from this study which indicate that 84.8% of pregnant women present at first antenatal visit with anemia (Hb 11g/dl) an 8.7% of their infants (n = 230) have a hemoglobin at birth below 14g/dl. There is an association between pregnancy anemia and malaria. A case control study in pregnant women and an infant cohort study to 18 months of age, are employed to study the cause and effects of anemia and malaria on women and their infants health.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Present development concerning antimalarial activity of phospholipid metabolism inhibitors with special reference to in vivo activity.

The systematic screening of more than 250 molecules against Plasmodium falciparum in vitro has previously shown that interfering with phospholipid metabolism is lethal to the malaria parasite. These compounds act by impairing choline transport in infected erythrocytes, resulting in phosphatidylcholine de novo biosynthesis inhibition. A thorough study was carried out with the leader compound G25, whose in vitro IC50 is 0.6 nM. It was very specific to mature parasites (trophozoïtes) as determined in vitro with P. falciparum and in vivo with P. chabaudi -infected mice. This specificity corresponds to the most intense phase of phospholipid biosynthesis activity during the parasite cycle, thus corroborating the mechanism of action. The in vivo antimalarial activity (ED50) against P. chabaudi was 0.03 mg/kg, and a similar sensitivity was obtained with P. vinckei petteri, when the drug was intraperitoneally administered in a 4 day suppressive test. In contrast, P. berghei was revealed as less sensitive (3- to 20-fold, depending on the P. berghei-strain). This difference in activity could result either from the degree of synchronism of every strain, their invasion preference for mature or immature red blood cells or from an intrinsically lower sensitivity of the P. berghei strain to G25. Irrespective of the mode of administration, G25 had the same therapeutic index (lethal dose 50 (LD50)/ED50) but the dose to obtain antimalarial activity after oral treatment was 100-fold higher than after intraperitoneal (or subcutaneous) administration. This must be related to the low intestinal absorption of these kind of compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Relation of amniotic fluid C-peptide levels to neonatal body composition.

OBJECTIVE: To compare the correlation between fetal insulin production (as estimated by amniotic fluid [AF] C-peptide concentration) and neonatal body fat (as estimated by both anthropometrics and total body electrical conductivity) with that between fetal insulin production and birth weight or fat-free mass. METHODS: Amniotic fluid C-peptide concentration measured within 1 week of delivery was correlated with birth weight and neonatal body composition, estimated by both anthropometric measures and total body electrical conductivity within 24 hours of birth. Eighteen term neonates were studied: 13 from pregnancies complicated by diabetes and five from mothers with normal glucose tolerance. RESULTS: Six infants were large for gestational age and 12 were appropriate for gestational age. There was a significant correlation between AF C-peptide level and neonatal fat mass, estimated by either anthropometric measures (r = 0.72, P = .0008) or total body electrical conductivity (r = 0.61, P = .008) methodology. The correlation was weaker between AF C-peptide level and either ponderal index (r = 0.44, P = .064) or total weight (r = 0.39, P = .11). The correlation with fat-free mass estimated by either method was not statistically significant. CONCLUSION: Our results suggest that fetal insulin production, as estimated by AF C-peptide concentration, influences fetal growth primarily through increasing fetal fat deposition rather than lean body mass.

Amniocentesis↗
PubMed1993

The synaptic vesicle-associated protein amphiphysin is the 128-kD autoantigen of Stiff-Man syndrome with breast cancer.

Stiff-Man syndrome (SMS) is a rare disease of the central nervous system (CNS) characterized by progressive rigidity of the body musculature with superimposed painful spasms. An autoimmune origin of the disease has been proposed. In a caseload of more than 100 SMS patients, 60% were found positive for autoantibodies directed against the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD). Few patients, all women affected by breast cancer, were negative for GAD autoantibodies but positive for autoantibodies directed against a 128-kD synaptic protein. We report here that this antigen is amphiphysin. GAD and amphiphysin are nonintrinsic membrane proteins that are concentrated in nerve terminals, where a pool of both proteins is associated with the cytoplasmic surface of synaptic vesicles. GAD and amphiphysin are the only two known targets of CNS autoimmunity with this distribution. This finding suggests a possible link between autoimmunity directed against cytoplasmic proteins associated with synaptic vesicles and SMS.

Autoantigens↗