Satellite association in Down's syndrome

Summary The frequency of association of acrocentric chromosomes is examined in 20 Down's syndrome children, their parents, and 60 controls. Chromosome 21 enters into satellite associations most frequently, and chromosome 15 least. The parents of Down's syndrome children do not show any increased tendency for satellite association of chromosome 21 or indeed any other acrocentric.     

Familial Down's syndrome.

A family is reported in which the same mother conceived two children with trisomy 21. The pregnancy with the second affected child was interrupted after diagnostic amniocentesis. Maternal chromosome analysis was normal. This family and those previously reported suggest that there is an increased recurrence risk of trisomy 21 after the birth of an affected individual, possibly caused by a genetic tendency for non-disjunction. After the birth of a child with Down's syndrome, amniocentesis and chromosome analysis of cultured amniotic fluid cells is indicated in each further pregnancy, irrespective of maternal age.     

Chromatin structure in Down's syndrome.

In the chromatin of patients with Down's syndrome, changes are shown to occur in a short-term lymphocyte culture of the human peripheral blood. Some of them are induced by the patient's blood serum and are reversible when this is replaced by normal serum. A 100-fold dilution of the blood serum taken in subjects with Down's syndrome does not produce any changes in the structure of the lymphocyte chromatin of the patients. A similar procedure with the blood serum of healthy donors resulted in a drastic activation of their lymphocyte chromatin. These experiments, and investigations on the effect produced by the blood serum on the model desoxyribonucleoprotein systems, support the suggestion that the changed state of the chromatin in subjects with Down's syndrome is caused by a complex set of components contained in the blood serum, whose degree of dissociation deviates from the normal.     

HL-A frequencies in Down's syndrome.

HL-A antigen frequencies were examined in 76 Down's syndrome individuals and 733 normal Caucasians. 10 antigens of the first locus and 15 antigens of the second locus were defined, using a microlymphocytotoxicity technique. No significant differences were observed between the normal and Down's syndrome samples, in contrast to a previous report (Boxer and Yokoyama, 1972) of decreased HL-A antigen frequencies in Down's syndrome individuals. Our results therefore suggest that there is no relationship between trisomy 21-associated immune aberrations and altered HL-A antigen frequencies.     

Down's syndrome in British Columbia Indians

An investigation into the incidence of Down''s syndrome in British Columbia Indians disclosed that this was little different from that in the non-Indian population. The clinical features of the condition are common to both groups.     

Blood cell phosphofructokinase in Down's syndrome

Summary Measurement of erythrocyte phosphofructokinase (PFK) activity in Down's syndrome failed to confirm the nearly 50% increase reported by others. An increase of 29% was found, while leukocyte PFK activity was normal. Erythrocyte PFK differs immunochemically from platelet and leukocyte PFK, and the enzyme is probably genetically heterogeneous; therefore, it remains possible that a structural gene for erythrocyte PFK is present on chromosome 21.This work was supported in part by grant FR-05355 (M.M.C.) and grant AM-12588 (R.B.L.) from the National Institutes of Health. Dr. Layzer is the recipient of Career Development Award NB-35310 from the National Institute of Neurological Diseases and Stroke.