Duchenne muscular dystrophy in one of monozygotic twin girls

Monozygotic twin girls are reported, one of whom has the typical clinical features of Duchenne muscular dystrophy despite a normal female karyotype. Although certain features of the biopsy were atypical, the clinical diagnosis was supported by persistent markedly raised blood creatine kinase levels and findings typical of DMD on electromyography and magnetic resonance spectroscopy. Analysis of an X linked DNA polymorphism in 16 independent somatic cell hybrids made between cells derived from each girl and a mouse line suggest that in one twin only the maternal X chromosome is active, whereas in the other the active X was paternally derived. More data are needed to exclude sampling error. These preliminary experimental results support the hypothesis that both girls are heterozygous for Duchenne muscular dystrophy. X inactivation, by chance, resulted in two contrasting cell masses with different active X chromosomes. This segregation was followed by, and may even have resulted in, twinning into a female pair, one normal and one with the full clinical features of the disease.

First trimester prenatal diagnosis and detection of carriers of haemophilia A using the linked DNA probe DX13

Although the use of a gene specific deoxyribonucleic acid (DNA) probe is the method of choice for detecting carriers of genes for rare genetic disorders, there will always be families in which such probes cannot be used because key subjects are not informative for restriction fragment length polymorphisms in or around the gene. In these cases closely linked DNA markers have to be used. An X chromosome specific DNA probe, DX13, which is closely linked to the haemophilia A locus on the X chromosome, was used for early prenatal diagnosis in two cases and to detect carriers in a series of nine possible heterozygote women. The first reported crossover between DX13 and the factor VIII:C locus was observed in this study. There are complexities inherent in using any linked DNA probe for assignment of genes, but such techniques are clinically important.

Linkage studies of X-linked mental retardation: high frequency of recombination in the telomeric region of the human X chromosome (fragile site/linkage/recombination/X chromosome)

One of the commonest forms of X-linked mental retardation is associated with a fragile site at Xq27 on the human X chromosome which can be visualised structurally after culturing cells in folate-deficient media. Unusually, the mutation can be transmitted through a phenotypically normal male. There is already some evidence that the gene loci for G6PD and factor IX are linked to this mental retardation locus. We have followed the inheritance of a DNA sequence 52A, in fragile site families that are also informative for factor IX. We demonstrate that these probes are localised at Xq27/Xq28-Xqter, close physically to the fragile site. We did not find close linkage between 52A, factor IX, and the fragile site in the families studied despite 52A and factor IX showing linkage in normal families. We discuss the importance of these data for the genetic mapping of this region of the human X chromosome and the implication for the use of these DNA probes for clinical diagnosis.

Pathogenic free-living amebae. Immunocytologic demonstration and species identification

This report describes methods for preparation, immunologic marking, and staining of amebae in formalin-fixed brain tissue, and in exudates, discharges and body fluids. The suggested procedures provide slide preparations of unknown specimens together with known amebae from cultures as controls, all on a single slide for each antiserum. This allows for cytologic studies of host cells, morphology of the amebae present, and specific immune marking of the amebae by use of immune sera and protein A Staphylococcus. Such preparations may also be used for immunoperoxidase and immunofluorescence. The need for the utilization of direct microscopic examination by the methods suggested here, or comparable ones, is discussed.

A clinically useful DNA probe closely linked to haemophilia A

Genetic linkage studies were done in families segregating for haemophilia A with an X-chromosome-specific probe, DX13, which has been localised to band Xq28. When DNA is digested with the restriction enzyme Bg1 II, this probe recognises a restriction fragment length polymorphism, for which 50% of females are heterozygous. No crossovers were seen between the haemophilia A locus and the DX13 locus (lod score = 5.4 at recombination fraction [theta] 0.0; 95% confidence limits of theta, 0-12%). This indicates that the DX13 probe is closely linked to the haemophilia A locus and is likely to prove useful in carrier detection and prenatal diagnosis.

Use of a chromosome 21 cloned DNA probe for the analysis of non-disjunction in Down syndrome

A recombinant clone was isolated containing a sequence which occurs only on human chromosome 21 and defines a two-allele restriction fragment length polymorphism showing Mendelian inheritance. Forty seven percent of the London population are heterozygous for the polymorphism. The chromosomal location of the DNA sequence homologous to the probe was confirmed using rodent-human somatic cell hybrids. DNA from persons with Down syndrome and from their parents was analysed. It was possible to confirm trisomy 21 by dosage hybridisation to Southern blots, and to determine the origin of the supernumerary chromosome. The technique will be of use for determination of the paternal or maternal origin of nondisjunction in cases of Down syndrome which are not informative using existing markers.

Identification of an autosomal locus affecting steroid sulfatase activity among inbred strains of mice

We have found an activity variant for testicular and liver steroid sulfatase among inbred strains of mice that is not X-linked. C57BL/6J, SM/J and SWR/J testicular extracts hydrolyze 3H-dehydroepiandrosterone sulfate twice as rapidly as do A/J extracts. The C3H/HeJ and DBA/2J strains were intermediate. The Km values for C57BL/6J and A/J are 2.29 +/- 0.10 and 1.01 +/- 0.02 microM, respectively. The F1 values in both directions were intermediate, which argues against X-linkage of this trait. F2 values show scattered high-intermediate-low values compatible with assay variation superimposed on the segregation of codominant alleles. When assayed for both testicular and liver steroid sulfatase, nine recombinant inbred lines between A/J and C57BL/6J segregate to near the parental strain values. Thus, this activity variation for steroid sulfatase appears to be determined by a single gene, which is not X-linked. Sex and steroidal hormone differences in liver steroid sulfatase activity were not present in the A/J strain, but females of the C57BL/6J and some recombinant inbred lines had higher levels. Electrophoretic studies only disclosed a variant in the SM/J strain, which seems to be secondary to the well-known neuraminidase variation in SM/J.

Genetic aspects of the effects of methylmercury in mice: the incidence of cleft palate and concentrations of adenosine 3':5' cyclic monophosphate in tongue and palatal shelf

Concentrations of adenosine 3':5' cyclic monophosphate (cAMP) were measured in the tongues and palates of 14.5-day-old fetuses from control and methylmercury-treated mothers of four inbred lines of mice which represent the four possible combinations of two H-2 alleles and two residual genetic backgrounds. The incidence of cleft palate in fetuses from control and methylmercury-treated mothers was also examined. The H-2 alleles significantly affected the degree of reduction of cAMP concentration in palates seen in fetuses from mothers treated with methylmercury. Neither the H-2 allele nor the residual genetic background played a role in the effect of methylmercury on cAMP concentrations in fetal tongues. The magnitude of increase in the incidence of cleft palate with methylmercury treatment was approximately the same for all lines. Thus, methylmercury-induced cleft palate may not be mediated by the reduction of cAMP. Finally, fetuses with cleft lip had increased palatal cAMP levels, whether or not they were from control or methylmercury treated mothers.

Variation in spermatozoal levels of phosphoglycerate kinase-2 in mice

Litter size differences exist between inbred strains of mice with high and low spermatozoal phosphoglycerate kinase-2 activity, but an examination of these two variables in recombinant inbred lines between the two strains suggest that the variables are not related. An examination of spermatozoal cAMP concentrations in these recombinant inbred lines demonstrated no correlation with litter size. Furthermore, spermatozoal cAMP concentrations were demonstrated to be under multigenic control.

Surface coagglutination with formalinized, stained protein A staphylococci in the immunologic study of three pathogenic amebae

The indirect immunofluorescence and, to a lesser extent, the immunoperoxidase methods have become the principal means of conducting immunological studies upon amebae. These procedures require the conjugation of fluorescein or enzyme with antiglobulin reagents and fixation of the amebae. The present report describes a somewhat similar methodology wherein formalinized, stained protein A staphylococci combined with specific antibody have been found to coagglutinate upon a portion of the amebic surface of living trophozoites in a fashion similar to direct immunofluorescence. The prepared staphylococci without attached antibody have also been found to coagglutinate in an identical fashion after the specific antibody has been deposited upon the amebic surface. This is comparable to indirect immunofluorescence reaction. A comparison of this procedure with the immunofluorescence method of identification and with measurement of titer of serum antibody is presented, which indicates that the new technique compares favorably with the immunofluorescence results.

A major autosomal gene effect on activity of glucose 6-phosphate dehydrogenase segregating between recombinant inbred lines of mice

G6PD measurements (expressed per g haemoglobin) in both males and females of the parental lines C57BL/6J and C57L/J and four recombinant inbred (RI) lines between them showed segregation of G6PD levels as parental classes (one line showed the higher C57BL/6J activity, three lines were indistinguishable from C57L/J). Haemoglobin also varied significantly among the parental and RI lines but this variation did not explain the variation in G6PD. NADP levels (expressed per g wet wt of erythrocytes) correlated with G6PD levels but one RI line was intermediate in males while two RI lines were lower than either parental line in females. Thus, the major autosomal locus affecting G6PD levels which segregates between these two inbred lines probably does not act directly on NADP levels. The variation in the G6PD levels in the four RI lines co-segregated with the brown coat color locus but the association is not significant because of the small number of RI lines available.

Immunological studies of the sperm-specific phosphoglycerate kinase-2 of mice

Antiserum was prepared to 500-fold purified PGK-2A from mouse testes. Depsite the apparent high purity of the immunizing antigen, double diffusion analyses showed two precipitin lines, one of which can be shown to correspond to PGK-2. An immunoabsorbent column of liver homogenate coupled to cyanogen bromid-activated Sepharose was used to remove the contaminating antibody. Both immuno-inactivation and double diffusion analyses demonstrated that the PGK-2 antigen appeared in testes between days 30 and 34 of postnatal development. The antisera prepared against highly purified PGK-2A did not disclose any immunological differences between PGK-2A, PGK-2B, and PGK-2C either by double diffusion analyses or quantitative immunoprecipitation. Antisera to PGK-2 did not inhibit in vitro fertilization of zona-free hamsters ova by mouse spermatozoa.

Comparative evaluation of a modified zinc sulfate flotation technique

A modified zinc sulfate flotation technique using Formalinized fecal specimens (F-ZnSO4) was compared to the Formalin-ether (FE) concentration method for the laboratory diagnosis of intestinal parasites. Many laboratories have difficulty storing, using, and disposing of either and need a procedure for concentrating fecal specimens which does not require ether. Comparative data were obtained for the recovery of protozoan cysts and helminth eggs and larvae from feces preserved in Formalin less than and longer than 1 month. Whereas the FE method was found generally to be more efficient, F-ZnSO4 was apparently more effective for the recovery of some species of parasites. F-ZnSO4 was not satisfactory for recovery of schistosome eggs. We conclude that, except for schistosomes, F-ZnSO4 compares favorably to the FE method for detecting infections of clinical significance.