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Biomedical subjects

N E Simpson

Publications and source records attributed to N E Simpson.

98 records · Page 6Linked to original sources
PubMedDate not supplied

Dermatoglyphic indices of males with the fragile X syndrome and of the female heterozygotes.

Indices for males with the fragile X [fra(X)] syndrome and for the female heterozygotes have been established. The indices were based on the increased frequencies of whorls and radial loops on the third digits of affected males and heterozygous females, increased frequency of arches on the third digits of the affected males, and an excess of low ab ridge counts and abnormal palmar creases, particularly the Sydney crease, in both sexes. The indices were calculated using the logN odds ratio based on the frequencies of the above dermatoglyphics and palmar creases in 47 males with the syndrome compared to 497 male controls and 36 heterozygous females compared to 493 female controls. The indices had similar distributions in males and females. Seventy per cent of males with the syndrome and 67% of female heterozygotes had an index greater than or equal to +0.5. Thirty-one per cent of female heterozygotes who had both the dermatoglyphic index calculated and their chromosomes examined under appropriate conditions for the fra(X) site had an index less than +0.5 and had less than 2% fragile sites (most had none). However when the two tests were considered together, only 4/35 (11%) of the heterozygotes would not have been identified using the two criteria. The data suggest that the dermatoglyphic index is a helpful adjunct test with chromosome analysis for the identification of fra(X) heterozygotes.

Adult↗
PubMedDate not supplied

An assessment of the use of flanking DNA markers for fra(X) syndrome carrier detection and prenatal diagnosis.

One hundred and three individuals in 11 unrelated families with the fragile-X [fra(X)] syndrome were tested for polymorphisms identified by probes flanking the fra(X) site at Xq27.3. Two probes distal and 2 proximal to the fra(X) site were used. Thirteen known female carriers were analyzed retrospectively. DNA markers gave probabilities of carrying the mutation of 99% in 1 female, 89% in 8 females, and 10-55% in the other 4 females. We also estimated the probability of having inherited the mutation for 16 individuals of unknown fra(X) status using DNA markers and corrections for incomplete penetrance. The DNA marker test gave risks for females of 1-6% (7 females), 15% (1 female), and 97% (1 female). In males the risks were 1-3% (6 males) and 91% (1 male). In 3 families, DNA marker data were used to calculate probabilities of greater than or equal to 98.5% that transmission of the fra(X) mutation had occurred through normal males. In the retrospective studies, only 1 of 7 retarded males could have been diagnosed prenatally as having the fra(X) mutation with a probability of 99%. DNA marker analysis was uninformative in 5 of these males. When fra(X) carrier status cannot be established by chromosome analysis, DNA marker studies provide an alternative test that can be used to calculate individual risks more precisely. However, linkage analysis of the probe loci in these 11 families suggests that the recombination frequency between the fra(X) locus and the factor IX gene (F9) and DXS52 may be greater than previously suggested. Until the true recombination frequencies are established and the question of heterogeneity among families is fully analyzed, caution in using DNA markers as a predictive test is advised.

DNA↗
PubMedDate not supplied

Assignment of multiple endocrine neoplasia type 2A to chromosome 10 by linkage.

Multiple endocrine neoplasis type 2A (MEN2A) is one of several kinds of cancers that appear to be inherited in an autosomally dominant fashion. We have assigned the MEN2A locus to chromosome 10 by linkage with a new DNA marker (D10S5). The linkage led us to investigate other chromosome 10 markers and demonstrate linkage between the disease locus and the interstitial retinol-binding protein (IRBP) gene. The D10S5 locus was sublocalized to 10q21.1 by hybridization in situ and the IRBP gene to p11.2----q11.2 with a secondary site at q24----q25. The linkages were established using 292 members of five families, three different restriction fragment length polymorphisms (RFLPs) at D10S5 and two RFLPs recognized by the IRBP probe. The recombination frequencies from pairwise linkage analysis between the disease and two marker loci D10S5 and IRBP were 0.19 and 0.11, with maximum lod scores of 3.6 and 8.0 respectively. Ordering of the three loci by multipoint analysis placed the IRBP gene approximately midway between the disease and D10S5 loci.

Chromosome Mapping↗
PubMedDate not supplied

Response of first order vestibular neurons to lidocaine hydrochloride.

Changes in behavior and electrical activity of primary vestibular neurons were observed following injection of lidocaine hydrochloride into the middle ear of cats. After injection the cats exhibited head and ocular nystagmus, head and neck deviation and pupillary changes. Mean preinjection resting discharge rate for first order vestibular neurons was 46.0 spikes/sec. Two hours after lidocaine application the resting rate decreased to a mean of 22.2 spikes/sec and then recovered to 43.0 spikes/sec four hours, and 47.4 spikes/sec six hours after the experimental treatment. The increment sensitivity (increased rate of firing) of horizontal canal neurons to constant angular acceleration for the control period was 2.0 extra spikes/sec/deg/sec2; two hours after the application, 70% of the recorded neurons were unresponsive to angular acceleration or tilt. The sensitivity after four hours was 1.0 spikes/sec/deg/sec2 and 2.1 spikes/sec/deg/sec2 at six hours. The distinct depression of sensitivity by lidocaine at four hours compared to normal mean resting rate at this time suggests these functions may be governed by two modes of action in the receptor or first order afferents.

Animals↗
PubMedDate not supplied

Binocular counterrolling in humans during dynamic rotation.

Seven subjects 18 to 66 years old underwent 360 degrees rotation at a constant velocity of 3 degrees/sec, in 27 trials beginning randomly right ear down or left ear down. A camera on the rotating chair photographed both eyes every 10 degrees. Dual projectors measured counterrolling, the image from one projector being aligned and rotated until it was superimposed on the image from the other. Right and left eyes were measured independently. The group reached maximum counterrolling at about 70 degrees and 270 degrees in rotations to the right, with values of about -6 degrees and 4 degrees respectively. Rotations to the left reached maximum at 50 degrees and 270 degrees with about 4.5 degrees and -5.25 degrees respectively. Individual subjects showed ranges of counterrolling varying from 4.03 degrees to 17.44 degrees, mean 11.30 degrees. More counterrolling was observed when subjects were tilted to right than to left. The downward eye counterrolled more than the upward. Amount of counterrolling was inversely correlated with age.

Adolescent↗