The problem of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a lethal X-linked muscular disorder. The biochemical defect remains unknown, but the gene responsible has been mapped to band Xp21. The gene has now been cloned in two laboratories solely from knowledge of its map location. L. M. Kunkel and his colleagues isolated genomic sequences (PERT 87) from within a large deletion causing DMD, whereas our group isolated genomic sequences (XJ) spanning the junction of an X-autosome translocation causing the disease. Chromosome walking by both groups has led to the isolation of over 400 kilobases of the PERT 87 and XJ region. Subclones of PERT 87 and XJ reveal restriction fragment length polymorphisms that segregate with the DMD gene in 95% of meioses, and fail to hybridize with DNA from about 8% of male patients. Selected subclones of PERT 87 and XJ contain exons that hybridize to muscle-derived complementary DNA (cDNA) clones. The cDNA clones detect a large (16 kilobase) message. Analysis of deletions, mutations and translocations suggests a DMD gene of between two million and three million base pairs. The clones obtained so far are useful for attempts to generate antibody against the gene product and for carrier identification and prenatal diagnosis.

The effects of high iodine on the brain development of mice

C57 mice were divided into two groups: (A): experiment group (H group). Each female mouse was injected with 20 microliter iodized oil; (B): control group (N group). Both groups were mated 8 days after iodized oil injection. Urine iodine contents/24 h of H group was 20 times higher than that in N group 7 days after injection and 18 times higher two months later. Serum T4 values were determined. Brain protein, DNA, body weight, motility and learning ability were measured in the progeny. The results indicate that there was no statistically significant difference between the groups in any of the parameters mentioned above. This strongly suggests that a high iodine dose, given as iodized oil, does not have obvious damaging effects on brain development, at least in mice.

Comparison of tissue preparation methods for assay of nicotinamide coenzymes

To prepare tissues for analysis of NAD(+), NADH, NADP(+), and NADPH, common practice is to freeze samples in liquid nitrogen, often followed by freeze-drying, before extraction in HCl or NaOH. With cucumber (Cucumis sativus L.) cotyledons, prefreezing in liquid nitrogen or slower freezing to -20 degrees C yielded substantially lower values for NADH and NADPH than obtained from samples homogenized immediately in acid or base. Freeze-drying after freezing in liquid nitrogen generally caused even lower values of those coenzymes. We suggest that direct extraction is more likely to yield accurate results with cotyledons and other plant parts.

A cDNA clone from the Duchenne/Becker muscular dystrophy gene

Duchenne muscular dystrophy (DMD) is the most common of the muscular dystrophies affecting one in 3,000 live male births. Both DMD and the mild form, Becker muscular dystrophy (BMD), are X-linked. There are a number of females affected by the disease who all possess an X-autosome translocation, with the exchange point in the X always occurring within chromosome band Xp21. This, together with linkage and deletion data, has localized the gene at band Xp21. DNA fragments from this region have been cloned using a patient with a large Xp21 deletion and from a patient with a t(X:21) translocation. The former clones (pERT 87) comprise the DXS164 locus and the latter clones (XJ) the DXS206 locus. Subclones from both regions allow the detection of deletions in approximately 11% of DMD patients. A fetal muscle complementary DNA clone corresponding to exons in the DXS164 locus has been isolated and detects a 16-kilobase (kb) transcript. We present the isolation of an adult muscle cDNA clone from the DXS206 locus that detects a 16-kb mRNA in adult human muscle. The cDNA clone contains exons that map in the DXS206 locus, the DXS164 locus, and on the centromeric side of these cloned regions. The t(X;21) translocation exchange points occurs within a large intron of 105 kb or larger, indicating that the translocation has disrupted the DMD/BMD gene to cause the disease in this patient.

Correlation of dietary aflatoxin B1 levels with excretion of aflatoxin M1 in human urine

Corn and peanut oil (total, 253 samples) were collected from 32 households in Fushui county of the Guangxi autonomous region of the People's Republic of China, where high liver cancer incidence has been reported, every day over a period of 1 week and analyzed for aflatoxin B1 (AFB). A total of 252 urine samples were collected simultaneously from the residents in the households which were shown to have consumed AFB and were analyzed for aflatoxin M1 (AFM) by a competitive direct enzyme-linked immunosorbent assay. A good correlation between total dietary AFB intake and total AFM excretion in human urine was observed during a 3-day study. A regression equation of 0.143 plus 0.0135 multiplied by the amount of AFB consumed was observed. Between 1.23 and 2.18% of dietary AFB was found to be present as AFM in human urine. A good correlation was also observed between the AFB concentration in corn and the AFM concentration in human urine. The results suggest that analysis of AFM in urine by enzyme-linked immunosorbent assay could be used as an index for human exposure of AFB in an extensive epidemiological study.

Hepatic damage in experimental and clinical paragonimiasis

The hepatic damage induced by Paragonimus skrjabini, and the migration route of this species and that of P. westermani, were investigated in a series of animal experiments and in 34 clinical and four autopsy cases of paragonimiasis. The major symptoms and signs of an unique case reported from Sichuan Province included hepatic tenderness, disturbance of hepatic functions, remittent fever, and cough with bloody sputum. Laparotomy revealed marked adhesions surrounding the liver, spleen and duodenum. Diagnosis was made by finding P. skrjabini in a bulla on the abdominal wall about 5 months after the onset of illness. After specific treatment with bithional, body temperature and liver functions returned to normal. Twenty-three of 33 cases independently studied from Fujian Province also showed similar hepatic function disturbance. Autopsy cases showed hepatic chronic eosinophilic abscesses with Charcot-Leyden crystals. Experimentally, P. skrjabini infection caused hepatic damage in all laboratory animals used. The main pathologic changes were initially acute eosinophilic abscesses in the liver, worms being found sometimes in the necrotic cavities of the abscesses; hepatomagaly also occurred. Some cysts containing mature worms were found in the liver of dogs 3-9 months after infection. Numerous eggs were deposited in the cyst walls. The migration route of P. skrjabini was studied in young dogs. Worms appeared in the liver initially on day 3 and reached their highest level on day 14. P. westermani also migrated into liver, but their numbers were less than those of P. skrjabini.