Clinical variability in a family with X-linked retinal dystrophy and the locus at the RP3 site

One large Australian family with X-linked retinal dystrophy was found to have extreme clinical variability in the hemizygotes. One member had the typical rod-cone disease, three had the cone-rod pattern and one had macroscopic changes in the macular area only, but with low potentials in the ERG. The locus for the disease was found to be distal to L1.28 at Xp21, the site for RP3. From a study of case histories reported it seems that clinical variability can be a common feature of X-linked retinitis pigmentosa (XLRP) with the locus at Xp11.3 (RP2) or at Xp21 (RP3), and this family may well be categorized as XLRP.

Effects of posture and sleep on the pharmacokinetics of paracetamol (acetaminophen) and its metabolites

The effects of posture and sleep on the pharmacokinetics of paracetamol (acetaminophen) 500 mg and its metabolites were studied in 8 healthy men. The mean residence times for paracetamol or its metabolites were significantly altered by change in posture or by sleep, whereas other pharmacokinetic parameters were unchanged. The change in mean residence time is consistent with a faster absorption of paracetamol during ambulation. The present data suggest that the proposed posture-related changes in volume of distribution do not exist, and that there is no pharmacokinetic basis for a headache being relieved by taking paracetamol and lying down.

Exclusion of the autosomal dominant retinitis pigmentosa gene from a substantial region of chromosome 1: study of a large Australian family

In an attempt to map the gene(s) responsible for autosomal dominant retinitis pigmentosa (ADRP), the technique of reverse genetics was used on a large multigenerational Australian pedigree. The family demonstrated a form of the disease which appears to be less severe than that observed in the Irish pedigree. It was typed for 10 restriction fragment length polymorphism (RFLP) markers on chromosome 1. The data from the linkage study was analysed using the programs LIPED 3; six markers gave informative results. The ADRP gene was excluded from this family from 102 cM using previously prepared chromosome 1 maps. This accounts for 36% of chromosome 1 which is estimated to be the longest human chromosome.

Localizing multiple X chromosome-linked retinitis pigmentosa loci using multilocus homogeneity tests

Multilocus linkage analysis of 62 family pedigrees with X chromosome-linked retinitis pigmentosa (XLRP) was undertaken to determine the presence of possible multiple disease loci and to reliably estimate their map location. Multilocus homogeneity tests furnished convincing evidence for the presence of two XLRP loci, the likelihood ratio being 6.4 x 10(9):1 in favor of two versus a single XLRP locus and gave accurate estimates for their map location. In 60-75% of the families, location of an XLRP gene was estimated at 1 centimorgan distal to OTC, and in 25-40% of the families, an XLRP locus was located halfway between DXS14 (p58-1) and DXZ1 (Xcen), with an estimated recombination fraction of 25% between the two XLRP loci. There is also good evidence for a third XLRP locus, midway between DXS28 (C7) and DXS164 (pERT87), supported by a likelihood ratio of 293:1 for three versus two XLRP loci.

X-linked megalocornea: close linkage to DXS87 and DXS94

In a family in which X-linked megalocornea is segregating, the disease locus was found to be closely linked to DXS87 (zeta max = 3.91, theta max = 0.00) and DXS94 (zeta max = 3.34, theta max = 0.00) in Xq21.3-q22.

Preliminary exclusion of an X-linked gene in Leber optic atrophy by linkage analysis

The maternal inheritance in Leber optic atrophy suggests that it may be caused by a cytoplasmic or mitochondrial defect. However, the strong male bias and the strict tissue specificity can not be readily explained by a single mitochondrial gene defect alone. Wallace suggested a hypothesis that the disease could be the result of an interaction between an X-linked gene and a mitochondrial DNA defect. Linkage relationships between Leber optic atrophy and 15 X-chromosome markers were analyzed in three large Tasmanian families. The results of two-point linkage analysis showed no close linkage between Leber optic atrophy and any of the 15 markers. The results of multipoint linkage analysis suggested the exclusion of the assumed X-linked gene from almost the whole X chromosome in these families.

Non-allelic mutations in X-linked retinitis pigmentosa

Using RFLP studies, the disease locus in two X-linked retinitis pigmentosa families was found to be centromeric to DXS7 in one family and telomeric to DXS7 in another, suggesting non-allelic heterogeneity.

Prenatal diagnosis and carrier detection by DNA studies in a Duchenne muscular dystrophy family with no living affected male

Restriction fragment length polymorphism studies and gene dosage analysis using the intragenic probes pERT87 were used to detect deletions in potential carriers in a family with Duchenne muscular dystrophy in which the only affected male was deceased. Two females were found to have inherited the paternal pERT87 alleles but not the maternal alleles, suggesting that they have inherited the pERT87 deletion from their mothers. The hybridization signals of pERT87 from these two females upon gene dosage analysis also suggested that they had a single copy of pERT87. The chorionic villi of a male fetus from one of these two females was found to be deleted for pERT87, suggesting that it was affected. This result confirmed the carrier status of the mother.

Extraperitoneal unilateral iliac artery bypass for chronic lower limb ischaemia

Extraperitoneal unilateral iliac artery bypass was used to treat chronic lower limb ischaemia in 105 patients (110 operations). This represented 20% of all operations for aorto-iliac disease. Unilateral iliac bypass was the preferred primary procedure for 99 operations, and was used to correct complications in one limb of a prior aortic bifurcation graft in the other 11. Ipsilateral femoropopliteal vein grafts were also performed in 45 legs (43%), prior to the iliac bypass in 18, as a synchronous operation in nine, and at a later date in 18 legs. This was a much higher proportion of combined operations than for patients by aortic bifurcation grafts (12%). Only 5 patients later required further proximal surgery, one for a blocked graft and four for contralateral iliac disease. The cumulative patency rate in surviving patients was 91% at 3 years. For the claudicants and for iliofemoral bypass operations, only one graft occluded, within 5 years, and no grafts occluded for operations where the superficial femoral artery was patent. The cumulative patency rates at 3 years were 85% for patients with critical ischaemia, 82% for ilioprofunda bypass operations, and 88% for operations where the superficial femoral artery was occluded. The cumulative foot-salvage rate in surviving patients initially treated for critical ischaemia was 77% at 3 years. The cumulative survival rate was 90% at 3 years. Extraperitoneal unilateral iliac bypass is now preferred as the primary operation for patients with apparent unilateral iliac disease causing severe ischaemia, if balloon dilatation is not appropriate or has failed.

Carrier detection in X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) by DNA restriction fragment length polymorphism studies

As part of a patient care and DNA research programme commenced in 1985, a number of DNA markers on the short arm of the X chromosome have been used to demonstrate restriction fragment length polymorphisms (RFLPs) segregating with the X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) gene. The analysis of the segregation of the RFLPs in 3 kindreds enables carrier detection, to a high degree of probability, in females at risk who are not manifesting symptoms and signs.

The use of field-inversion gel electrophoresis for deletion detection in Duchenne muscular dystrophy

Deletion is a common cause of Duchenne muscular dystrophy (DMD). Field-inversion gel electrophoresis, in conjunction with Southern blot hybridization, was used to detect large SfiI DNA fragments in the DMD locus. Two unrelated boys with DMD were found to have abnormal sized DNA fragments resulting from deletions. Some of the female relatives of these patients were also shown by this method to have deletions in the DMD locus.

Two different genes for X-linked retinitis pigmentosa

Linkage analysis was carried out in three large multigenerational kindreds with X-linked retinitis pigmentosa using DNA markers on Xp. About 10% recombination has been found between the retinitis pigmentosa locus (RP2) and the marker locus DXS7, assigned to band Xp11.3, which was reported earlier to be closely linked to RP2 in several independent families. In the kindreds described in this paper, however, RP2 shows close linkage and no recombination with the marker loci OTC and DXS148, both assigned to Xp21, indicating that, contrary to previous linkage studies, there is evidence of an RP locus distal to DXS7. This suggests that X-linked retinitis pigmentosa is genetically heterogeneous, i.e., caused by mutations at different loci.

Analysis of linkage relationships of X-linked retinitis pigmentosa with the following Xp loci: L1.28, OTC, 754, XJ-1.1, pERT87, and C7

A number of variants of X-linked retinitis pigmentosa (XLRP) have been described. In one variant, listed in the McKusick (McK) catalogue (McKusick 1983) as entry no. 30320, the heterozygotes exhibit a golden metallic or tapetal reflex. Three large pedigrees segregating for XLRP with the characteristic tapetal reflex in the heterozygotes were examined, and the linkage between the XLRP locus and Xp loci, L1.28, OTC, 754, XJ-1.1, pERT87 and C7 was measured. The strongest linkage was found to be between the XLRP locus and OTC. In addition, recombinational evidence drawn from the three pedigrees suggests that the XLRP locus is distal to L1.28 and proximal to 754. This putative location of the XLRP gene between L1.28 and 754 taken together with the tight linkage to OTC, a locus already located between L1.28 and 754, leads us to propose a gene order of centromere-L1.28-OTC/XLRP-754-telomere.

Palpation of the femoral and popliteal pulses: a study of the accuracy as assessed by agreement between multiple observers

Six vascular surgeons independently examined 44 legs in patients with suspected peripheral arterial disease. Each surgeon recorded whether the femoral and popliteal pulses were present or absent, and if thought to be present, whether they were normal or reduced in amplitude. Interobserver agreement was determined by calculating both observed agreement (Po) and agreement after correction for chance (kappa-k). The results were calculated both for each possible pair of surgeons and as an overall value for all possible pairs combined. Agreement as to whether pulses were present or absent was significantly better than expected by chance but was only moderately good (overall kappa for femoral pulse = 0.53, and overall kappa for popliteal pulse = 0.52). More often than not, agreement as to whether the pulses were normal or reduced was no better than expected by chance (overall kappa for femoral pulse = 0.15, and overall kappa for popliteal pulse = 0.01). For each assessment, agreement was no better for the more experienced than the less experienced pairs of surgeons. The results indicate that more objective methods than pulse palpation are required to determine whether there is significant disease in the aorto-iliac and femoro-popliteal arterial segments.

Analysis of deletions in DNA from patients with Becker and Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder for which the biochemical defect is as yet unknown. Recently, two cloned segments of human X-chromosome DNA have been described which detect structural alterations within or near the genetic locus responsible for the disorder. Both of these cloned segments were described as tightly linked to the locus and were capable of detecting deletions in the DNA of boys affected with DMD. In an attempt to determine more precisely the occurrence of these deletions within a large population of DMD patients and the accuracy of one of the segments, DXS164 (pERT87), in determining the inheritance of the DMD X chromosome, the subclones 1, 8 and 15 were made available to many investigators throughout the world. Here we describe the combined results of more than 20 research laboratories with respect to the occurrence of deletions at the DXS164 locus in DNA samples isolated from patients with DMD and Becker muscular dystrophy (BMD). The results indicate that the DXS164 locus apparently recombines with DMD 5% of the time, but is probably located between independent sites of mutation which yield DMD. The breakpoints of some deletions are delineated within the DXS164 locus, and it is evident that the deletions at the DMD locus are frequent and extremely large.

True aneurysm formation in femoropopliteal autogenous vein bypass grafts: two cases

This paper describes two cases of true atheromatous aneurysm formation within reversed autogenous saphenous vein used for femoropopliteal bypass graft. We note the rarity of this complication and review the literature for true aneurysm formation within vein grafts used for this and other bypass procedures.

In situ femoropopliteal and distal vein bypass for limb salvage--experience of 50 cases

The aim of this paper is to assess the in situ technique of saphenous vein femoropopliteal (and femorotibial) bypass for limb salvage, and to compare it with the reversed vein method of bypass. In our 3-year study, we have operated on 50 cases resulting in a graft patency and limb salvage rate of 78 per cent at 18 months and 72 per cent overall. There was a 2 per cent perioperative and 10 per cent overall mortality. Graft thrombosis was associated with a variety of factors, mostly notably a small vein (les than 4 mm), a low calf vessel anastomosis, wound sepsis and progressive proximal (inflow) disease. However, the strongest correlation was that between graft thrombosis and the extent of distal disease, as 11 of 12 cases with thrombosed grafts had grade 2 or 3 run-off. In our experience the in situ technique offers haemodynamic and technical advantages over the reversed vein method of performing straightforward femoropopliteal bypass. Moreover, the in situ technique has wider application in that it allows a smaller vein (greater than 2.5 mm) to be used and also makes anastomosis to a small calf vessel easier. In this series, 16 per cent of cases would have been considered unsuitable for the reversed vein method if 4 mm was accepted as the lower limit of size for a reversed vein graft.

An experimental study of the use of a carbon fibre patch as a hernia prosthesis material

Carbon fibre patches were inserted as prostheses into the dorsal lumbar fascia of rabbits. Their incorporation into the tissues was observed over a period of 15 weeks, and their mechanical properties were compared with those of implants made of a conventional Mersilene mesh. Although the mechanical properties of carbon fibre patches are initially poor, the development of a superior connective tissue response after several weeks suggests that a layered composite of carbon fibre and Mersilene with the latter giving initial strength may provide a useful material for clinical use as a hernia prosthesis.

Effect of posture and sleep on pharmacokinetics. I. Amoxycillin

The pharmacokinetics of amoxycillin in normal male volunteers was studied during the states of bedrest, sleep and ambulation. The absorption and disposition of amoxycillin in ambulatory subjects was found to be comparable to that reported previously by other workers. Serum amoxycillin concentrations were found to be significantly greater during ambulation than during bedrest and sleep. The difference in serum levels resulted from an increased apparent total serum clearance and amoxycillin renal clearance during bedrest and sleep compared to ambulation. No significant differences in the clearance was found between the states of bedrest and sleep. The change in renal clearance of amoxycillin during ambulation was attributed to a diminished renal blood flow. Although the terminal half-life of amoxycillin did not differ significantly, the apparent volume of distribution appears to be much greater during bedrest and sleep than during ambulation. This difference could be explained pharmacokinetically using a two compartment model. No significant difference was found between the rates of absorption of amoxycillin as reflected by the lag time and time to peak serum amoxycillin. The actual values for these parameters would suggest, however, that the absorption of amoxycillin is faster during ambulation than in bedrest and that the absorption rate during sleep is slowest. The clinical implications of the effect of posture and sleep on the pharmacokinetics of amoxycillin are discussed.

Biochemical and enzymic changes during erythrocyte differentiation. The significance of the final cell division

1. The haemoglobin content of developing erythroblasts was shown to increase rapidly when the cells completed the final cell division of erythroid development and passed from the dividing into the non-dividing cell compartment. 2. The activity of carbonic anhydrase was measured and shown to increase continually throughout erythroid differentiation. The activity increased most rapidly in the polychromatic stage. 3. Catalase activity did not increase significantly during erythroid differentiation until the reticulocyte stage. 4. The activity of four enzymes, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, adenosine deaminase and nucleoside phosphorylase, exhibited a similar pattern of change during erythroid differentiation. In the dividing cell compartment their activity was relatively high but exhibited a steep decline between the polychromatic stage and the orthochromatic stage, that is, as the cell completed its final cell division and moved from the dividing to the non-dividing compartment. After this the activity of these enzymes was stabilized at a relatively low value, and this activity persisted at such a value until the reticulocyte stage. 5. Lactate dehydrogenase activity also declined after the cell had crossed from the dividing into the non-dividing stage, but in this case the decline was less than in the case of the above four enzymes. 6. Adenylate kinase activity was relatively constant in the dividing cell compartment but exhibited a 60 percent increase when the cell passed from the dividing into the non-dividing compartment. 7. The cessation of cell division appears to coincide with a set of complex biochemical changes.