Healthy Heterozygotes Research Articles

153 ERYTHROCYTE ADENINE PRPP AVAILABILITY IN TOO TYPES OF APRT DEFICIENCY USING SILICON OIL METHOD

For the cause of 2, 8-dihydroxyadenine urolithiasis. Japanese type adenine phosnhorobosyltransferase (APRT) deficiency is common in Japan. Some homozygotes for the Japanese type APRT deficiency had no urolithiasis and were clinically healthy. APRT activity in erythrocyte from homozygotes of Japanese type APRT deficiency was at the same levels as the activity from the healthy heterozygotes for the complete APRT deficiency. For the diagnosis of Japanese type APRT deficiency we compared the erythrocyte adenine phosnhoribosylpyrophosphate (PRPP) availability of Japanese type APRT deficiency with complete APRT deficiency using silicon oil method. Homozygote of Japanese type APRT deficiency showed 4.3±2.7% (mean ± standerd deviation) of adenine PRPP availability and every patient showed the almost same PRPP availability. Heterozygote showed 86.0±6.0% of adenine PRPP availability in comparing to those of normal subjects. These results supported the same mutation in Japanese type APRT gene. While in a Japanese family of complete ARRT deficiency, adenine PRPP availability of homozygote vias undetectable and that of heterozygote was normal low (54.3% of mean normal activity). The adenine PRPP availability of heterozygote of complete APRT deficiency was diagnostically different from that of homozygote of Japanese type APRT deficiency.

Detection of late onset steroid 21-hydroxylase deficiency by capillary gas chromatographic profiling of urinary steroids in children and adolescents

Patients suffering from late onset 21-hydroxylase deficiency (LO-CAH) excreted only slightly higher amounts of 17-hydroxypregnanolone (17-OH-PO), pregnanetriol (PT) and 11-oxo-pregnanetriol (11-O-PT) than age-matched healthy controls. To discriminate between LO-CAH and virilization of unknown origin and precocious pubarche, we calculated the following ratios: (1) pregnanetriol to tetrahydrocortisone (PT/THE), (2) the sum of 17-OH-PO, PT and 11-O-PT (OHP-M) to the sum of THE, tetrahydrocortisol (THF) and allotetrahydrocortisol (a-THF) (C-M) and (3) 11-O-PT to C-M. The following patients were studied: 9 patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency-non-salt losing (CAH-NSL), never treated; 8 patients with CAH (NSL/SL: 3/5) off treatment; 10 patients with LO-CAH; 11 patients with virilization of unknown origin (prepubertal/pubertal: 5/6) and 9 patients with precocious pubarche. Healthy individuals and obligatory heterozygote carriers of comparable ages served as controls. LO-CAH showed increased ratios (median (range] of PT/THE: 2.27, (1.15-9.09), OHP-M/C-M: 2.30, (1.24-8.15), and 11-O-PT/C-M: 0.24, (0.13-1.23) compared to healthy individuals and heterozygous carriers: PT/THE 0.28, (0.03-0.57), OHP-M/C-M 0.23, (0.06-0.46) and 11-O-PT/C-M less than 0.01, (less than 0.01-0.06), respectively. The calculation of ratios, rather than absolute amounts seems to allow the detection of LO-CAH in a single spontaneously voided urine specimen. The clinical and measurable hormonal manifestations of LO-CAH occur at the same time.

JAPANESE PATIENTS WITH PARTIAL APRT DEFICIENCIES ACCOMPANIED WITH 2,8-DIHYDROXYADENINE LITHIASIS SYNTHESIZE MUTANT APRT WITH ALTERED KINETIC PROPERTIES WHICH DOES NOT FUNCTION IN VIABLE CELLS: 98

Although all Caucacian patients with 2,8-dihydroxyadenine urolithiasis completely lack adenine phosphoribosyltransferase (APRT), more than half of Japanese patients with the same lithiasis only partially lack APRT. The degrees of APRT deficiencies in these Japanese patients are broadly the same as healthy heterozygotes for complete APRT deficiencies. We found that cultured T-cells from the Japanese patients with partial APRT deficiencies were, like those from the patients with complete APRT deficiencies but unlike the heterozygotes, more than 100-fold less sensitive to adenine analogs, 6-methylpurine and 2,6-diaminopurine, suggesting that APRT of these Japanese patients is non-functional in viable cells, although it functions normally in test tubes. Therefore, it is not APRT activity in test tubes but whether APRT is functional in viable cells that is important for clinical symptoms (lithiasis). The mutant enzymes from four separate families were found to have reduced affinities to PRPP but not to adenine, and at physiological concentrations of PRPP, normal but not mutant enzymes showed significant activities. The mutant enzymes contained several other altered characteristics in common possibly suggesting that they are coded by a common mutant allele.

Natural killer cell activity and T subpopulations in thalassemia major.

Natural killer (NK) cell activity against K562 cell targets and the distribution of T cell subpopulations were investigated in the peripheral blood of 25 patients affected by beta thalassemia major, 18 clinically healthy heterozygotes, and 25 age-matched normal subjects. It was found that thalassemia major patients display augmented levels of NK activity [specific lysis 41.9 +/- (se) 4.5%], while thalassemic carriers behave as normal controls [specific lysis 34.6 +/- (se) 3.5%]. The increase of NK function was neither related to the splenectomy nor to the siderosis, but rather to the age and the amount of blood units that the patients had received. An imbalance of circulating T subsets with the helper/suppressor cell ratio significantly diminished (p less than 0.001) was also detected in homozygotes but not in carriers. The finding that NK function is enhanced in homozygous beta thalassemia might be of clinical interest in assessing the risk of development of malignancies in these patients.

High frequencies of inversions and translocations of chromosomes 7 and 14 in ataxia telangiectasia

The R-banding of more than 1100 lymphocytes and fibroblasts from 11 patients with ataxia telangiectasia (AT) showed rearrangements of chromosomes 7 and/or 14 in about 7% of the cells. Among these rearrangements, pericentric inversion of chromosome 7 was the most frequent, and the paracentric inversion of chromosome 14 not very rare. These inversions are believed to be fairly specific of AT, and their absence in the previously reported literature may be due to technical problems. Inversions were also observed in the lymphocytes of presumed heterozygote carriers with a lower frequency, and may be of some help for the detection of healthy heterozygote carriers of the AT gene.

Survival and Herpes virus production of normal and xeroderma pigmentosum fibroblasts after treatment with formaldehyde

The survival of excision-deficient and of excision-proficient (variant) skin fibroblasts from xeroderma pigmentosum (XP) donors was about 5 times and twice, respectively, more sensitive to formaldehyde (FA) treatment than that of skin fibroblasts from healthy and XP heterozygote donors. The capacity of FA-treated host cells to further support Herpes virus (HSV) replication was also more sensitive to FA in XP12BE (group A) than in normal (KD) cells. An important recovery of this capacity occurred in both cell types when they were infected at increasing times (up to 36 h) after FA treatment. This contrasts with the decreasing capacity observed in XP12BE when similarly infected at increasing times after exposure to ultraviolet. In addition, the survival of FA-treated HSV was comparable in KD and XP12BE cells, whereas that of UV-irradiated HSV was much lower in XP12BE than in KD cells.

The Urinary Excretion of Radiocopper in Presymptomatic and Symptomatic Wilson's Disease, Heterozygotes and Controls: Its Significance in Diagnosis and Management

Radiocopper (64Cu, 67CU), given intravenously, has been used to study the pattern of excretion of copper in patients with presymptomatic, symptomatic and treated Wilson's disease, together with heterozygotes for the Wilson's disease gene and a control group of patients with a variety of neurological lesions mimicking Wilson's disease. Urine was collected for three periods after injection, 0 to 8 hours, 8 to 24 hours, at which time a test dose of penicillamine was given, and from 24 to 30 hours. Stable (endogenous) copper was also estimated on these samples and specific activity was determined. This was multiplied by a correction factor to allow for variations in dose and body weight. The findings for stable copper in urine were largely predictable. Controls and heterozygotes had the least copper excretion, the amounts rising in the presymptomatic to a peak in the symptomatic patients. Institution of therapy was associated with a fall in copper excretion pro rata with time. The most important radiochemical findings were as follows. Heterozygotes excreted less of the injected copper than controls both under basal conditions and after penicillamine. Presymptomatic patients excreted less radiocopper than heterozygotes after penicillamine although the excretion during the basal 24 hour period was very much greater. Patients with symptomatic Wilson's disease had by far the highest excretion of radiocopper in all three time periods which fell after treatment, pro rata with time, as had been found for stable copper. These results were subjected to computer analysis. There was no overlap between the various groups with the exception of a single control subject who had combined pyramidal and extrapyramidal system degeneration of obscure aetiology. This patient was classified by the computer study as 'heterozygote'. These findings lend further support to the hypothesis that the loss of a single gene for copper balance can be detected with a high degree of accuracy and also that presymptomatic patients can be selected from a sibship for prophylactic treatment without the risk of subjecting healthy heterozygotes to unnecessary and potentially hazardous long-term therapy.

The determination of heterozygosity for phenylketonuria

A method is described for detecting the healthy heterozygote carriers of phenylketonuria, both for eugenic counseling and as a diagnostic aid in distinguishing typical from atypical phenylketonuria. The plasma phenylalanine/tyrosine molar ratio (which can be taken as an index of heterozygosity) was determined in a group of 60 proven heterozygotes for phenylketonuria and a group of 161 normal individuals. In the normal individuals sampled the phenylalanine/tyrosine molar ratio varied from 0.52 to 1.04, whereas in the heterozygotes it ranged from 1.08 to 1.98. There was no zone of overlap between the 2 groups. This was probably due to the high accuracy of the analytical method, which is based on a new automatic system for analysis of amino acids by ion-exchange chromatography that performs 4 phenylalanine/tyrosine determinations/h, and to the method of preparation and preservation of the sample to be analyzed, developed at the RBM laboratories.

A molecular defect in thrombasthenic platelets.

An IgG antibody found in the serum of a thrombasthenic patient reacted in complement fixation with platelets from 350 normal individuals but was nonreactive with platelets from eight other thrombasthenic patients. ADP-induced aggregation of normal platelets was inhibited by the patient's antibody. Family studies using the quantitative complement fixation test showed that healthy heterozygotes were easily distinguishable from normal or thrombasthenic individuals since their platelets had an intermediate amount of the reactive antigen. Indirect immunoprecipitation tests using this serum and soluble membrane antigens labeled with iodine-125 that had been extracted from normal platelets by the detergent Nonidet P-40 gave a single radioactive peak at 120,000 mol wt in sodium dodecyl sulfate polyacrylamide gel electrophoresis. A similar estimate of the molecular weight was obtained from Sephadex G-200 filtration of the soluble antigens extracted from normal platelets by spontaneous release or chaotropic agents and tested in complement fixation with the patient's serum. These findings strongly suggest that the molecule recognized by this antibody is absent or structurally modified in thrombasthenia cases and that it may be involved in platelet aggregation.