Thermolabile methylenetetrahydrofolate reductase (C677T): frequency in the Irish population.

BACKGROUND: The genetic variation which underlies the thermolability and low enzyme activity of 5,10-methylenetetrahydrofolate reductase (MTHFR; C677T) has been extensively studied in many populations, including the Irish population. AIM: To describe the examination of the C677T substitution in two new control samples drawn from the Irish population. METHODS: A collection of 487 serum samples was obtained through the blood transfusion services of both the Republic of Ireland and Northern Ireland and a further 115 samples from volunteers. RESULTS: In both samples, the frequency of the thermolabile/low enzyme activity allele (T) was higher than that previously reported for the Irish population. CONCLUSION: This finding thus supports the need for a greater use of internal control/family-based association studies, as opposed to the classic case control study design, when assessing the contribution of the MTHFR T allele to disease processes.

Postprandial factor VII metabolism: the effect of the R353Q and 10 bp polymorphisms.

Elevated levels of coagulation factor VII activity (FVIIc) are associated with increased risk of CHD. FVIIc is strongly determined by two polymorphisms (R353Q and 0/10 base pairs (bp)) and plasma triacylglycerol (TAG) concentrations. The Q and 10 bp polymorphisms show strong linkage disequilibrium and have been associated with lower levels of fasting FVII, but there has been little investigation of the effect of these genotypes on the postprandial FVII metabolism. The present study demonstrated that fasting activated factor VII (FVIIa) and factor VII antigen (FVIIag) levels were significantly lower in the heterozygotes carrying the Q and 10 bp alleles (n 12), than in the R/0 bp homozygotes (n 12) (43.0 (SE 4.8) v. 23.9 (SE 6.5) mU/ml and 85.7 (SE 5.4) v. 71.6 (SE 7.5)% respectively). During postprandial lipaemia there was a significant increase in FVIIa in R/0 bp homozygotes but not in the heterozygotes carrying the Q and 10 bp alleles. The proportion of FVIIa (FVIIa:FVIIag) increased in the homozygotes but not in the heterozygotes (2.04 (SE 0.35) v. 1.20 (SE 0.26) respectively). Therefore possession of the relatively common Q and 10 bp alleles is not associated with postprandial activation of FVII, which may in turn have a protective effect against CHD.

Wallaby serum amyloid A protein: cDNA cloning, sequence and evolutionary analysis.

A serum amyloid A (SAA) clone was isolated from a Tammar wallaby cDNA library, the most distantly related mammalian species for which an SAA has been described to date. The clone predicts a premolecule of 127 amino acids with good homology to other mammalian SAAs, and consists of an 18 residue leader peptide and a mature protein of 109 amino acids. Evolutionary analysis at both the protein and nucleotide level indicate that the wallaby SAA clone clusters with the acute phase SAAs. However, as the SAA superfamily has undergone concerted evolution it is not possible to determine at this point which acute phase SAA it is most like. The grouping of wallaby SAA inside the acute phase SAA cluster demonstrates that at least some of the duplication events giving rise to multiple acute phase genes occurred prior to the divergence of the eutherian and metatherian mammals.

Effect of a partial report visual cue on information available in tachistoscopic presentations of alphanumeric characters varying in number and type.

The capacity of iconic memory is investigated using a variety of cueing techniques. As an alternative to auditory recall cues, a tachistoscopically presented arrow, with two exposure-fields at different luminances, was employed in a partial report paradigm. Alphanumeric target stimulus arrays varied in number and type. Results with 12 normal adults indicated that subjects recalled fewer items when the target array contained nine elements, as opposed to six, and when the visual cue was presented at a higher luminance. In all cases, numbers appeared easier to recall than letters. In general, subjects had less information available for recall than reported in previous studies employing auditory cues. It is possible that the effects observed are the result of backward masking by the visual cue. Nevertheless, subjects' performance suggests that the visual modality should not necessarily be abandoned for recall cueing.

Effect of diazepam on visuomotor reaction time.

20 male and 10 female adult, normal, healthy subjects, whose mean age was 26.34 yr., participated in a double-blind study of the effect of a single dose (0.2 mg./kg. of body weight) of diazepam on visuomotor reaction time. Reaction time was measured before drug administration, and 60 min., and 120 min. after administration. Separate reaction times for the dominant and nondominant hand were recorded. There were no significant differences between the diazepam and placebo group at each of the three time intervals. Diazepam in the single dose employed does not appear to affect adversely visuomotor reaction time of relatively young, normal, healthy adults. For both groups the difference in visuomotor reaction time between the dominant hand and the nondominant hand was statistically significant as expected.

Critical stimulus durations for some verbal and nonverbal stimuli.

Durations of stimulus exposures in visual backward masking are determined with reference to critical stimulus durations. These are defined as the minimum, undisrupted, durations of exposure for 100% accuracy for a predetermined number of trials. These durations are shown to vary both within and between classes of stimuli for 10 normal adults with a mean age of 26.40 yr. The verbal stimuli employed (letters of the alphabet) were significantly easier to discern than the nonverbal stimuli (arrows). Although some letters were more readily identified than others, differences were not significant. The results suggest that type of stimuli, nature of response, and the ease with which stimuli can be discerned be considered in the selection of target stimuli for experiments using masking.

Anterior-posterior locus of lesion and personality: support for the caudality hypothesis.

Investigated the effects of discrete brain lesions on MMPI performance in well-matched samples of patients with anterior and posterior injuries. Because of the nature of the samples and careful matching for potentially confounding variables, particular emphasis could be given to the study of brain-behavior relationships. Patients with posterior lesions produced a significantly more abnormal composite MMPI profile, had a consistent tendency to produce elevated (70+) individual MMPI scales, and had individual profiles that were universally rated as abnormal using standard criteria. The differential MMPI patterns exhibited by these two samples were compatible with traditionally held clinical hypothesis with regard to distinct personality differences secondary to focal lesions in the caudal plane. It is our conclusion that lesion caudality does have a differential effect upon MMPI performance when factors such as cognitive, motor, and sensory defects are controlled adequately. The implications are that this effect is locus specific and is not necessarily related to the degree of other neurobehavioral impairment, as has been hypothesized previously.

Parental consanguinity and the Majewski syndrome.

We report a female infant with the Majewski syndrome, one of a group of conditions characterised by short ribs, polydactyly, dwarfism, and early neonatal death. This syndrome seems to be extremely rare, with only five well documented cases reported and, including this case, nine recorded in all. The Majewski syndrome is considered to be recessively inherited, and this report adds further support to this hypothesis, as the infant was born to consanguineous parents.