Holt-Oram syndrome is a genetically heterogeneous disease with one locus mapping to human chromosome 12q.

Holt-Oram syndrome (HOS) is an autosomal dominant condition affecting the heart and upper limbs. We have sought to identify the location of this gene using microsatellite DNA markers in a linkage study. Of seven families analysed, five show linkage between HOS and markers on chromosome 12q. But the two remaining families, phenotypically indistinguishable from the others, do not show this linkage. Analysis with the computer program HOMOG indicates that HOS is a heterogeneous disease. Our analysis places one HOS locus in a 21 cM interval in the distal region of chromosome 12q. The localization of a gene for HOS, reported here, represents an important step towards a better understanding of limb and cardiac development.

Holt-Oram syndrome is caused by mutations in TBX5, a member of the Brachyury (T) gene family.

Holt-Oram syndrome is a developmental disorder affecting the heart and upper limb, the gene for which was mapped to chromosome 12 two years ago. We have now identified a gene for this disorder (HOS1). The gene (TBX5) is a member of the Brachyury (T) family corresponding to the mouse Tbx5 gene. We have identified six mutations, three in HOS families and three in sporadic HOS cases. Each of the mutations introduces a premature stop codon in the TBX5 gene product. Tissue in situ hybridization studies on human embryos from days 26 to 52 of gestation reveal expression of TBX5 in heart and limb, consistent with a role in human embryonic development.

Acquired pericentric inversion of chromosome 9 in acute myeloid leukemia.

Pericentric inversion of chromosome 9 involving the qh region is relatively common as a constitutional genetic aberration without any apparent phenotypic consequences. However, it has not been established as an acquired abnormality in cancer. Among the three patients reported so far in the literature with acquired inv(9), only one had acute myeloid leukemia (AML). Here we describe an unique case where both chromosomes 9 presented with an acquired pericentric inversion with breakpoints at 9p13 and 9q12 respectively, in a AML patient with aberrant CD7 and CD9 positivity. Additionally, one der(9) also showed short arm deletion at 9p21 to the centromeric region and including the p16 gene. The constitutional karyotype was normal. This is probably the first report describing an acquired inv(9) involving both chromosomes 9 in AML. The possible significance of this inversion is discussed.

Trisomy 21 as a sole acquired abnormality in an adult Omani patient with CD7- and CD9-positive acute myeloid leukemia.

We describe a case of acute myeloid leukemia (AML) in which trisomy 21 was the sole acquired cytogenetic abnormality. The immunophenotype showed positivity for CD7 and CD9 along with CD13, CD33, and CD34. The chromosomal analysis of bone marrow showed 47,XY +21 in all the metaphases analyzed. The constitutional karyotype was normal. The patient was an adult and did not have any features of Down's syndrome. The bone marrow morphology was AML-M2 as per the French-American-British (FAB) criteria. A final diagnosis of CD7- and CD9-positive AML-M2 was established with trisomy 21 as a sole cytogenetic abnormality. The patient responded remarkably well to chemotherapy and achieved complete clinical remission. This is the first case of CD7- and CD9-positive AML with trisomy 21 as a sole abnormality. A putative role for the co-expression of abnormal lymphoid markers in achieving quick remission is discussed.

Tightly linked polymorphic markers for fragile X syndrome and prenatal cytogenetic diagnostic experience.

Linkage analysis using the polymorphic loci DXS369, DXS296, DXS297 and DXS306 was carried out on a cohort of 17 families segregating for fragile X syndrome. The observed recombination fractions at: DXS369 (Zmax = 3.02; theta = 0.06), DXS297 (Zmax = 2.92; theta = 0.0), DXS296 (Zmax = 3.82; theta = 0.0), DXA306 (Zmax = 4.55; theta = 0.05) confirm that these loci are tightly linked to FRAXA. Our experience in the cytogenetic analysis of 58 at risk pregnancies by chorionic villus or fetal blood sample examination documents a false negative rate in obligate carrier male pregnancies for CVS of 11% and for FBS of 3%.

A method for studying antibiotic concentrations in inflammatory exudate.

A new technique is described for studying antibiotic concentrations in an experimental inflammatory exudate in vivo. In most exudates concentrations of four antistaphylococcal drugs which were of potential therapeutic significance could be assayed, and fucidin appeared to diffuse best. Higher concentrations of all antibiotics gained access to the lesion in the first two hours of inflammation, suggesting that their mobility did not depend on binding to cells during the inflammatory response. The technique may ultimately help to elucidate the relationship between antibiotics and host defences at the primary sites of infection.

Phagocytic cells in the human inflammatory response.

Human phagocytic cells are of crucial importance in the early responses to infection. However, tests of their function have been somewhat neglected in immunological screening. This paper summarises briefly our techniques for studying neutrophils and monocytes in skin abrasions and a simple assay of phagocytic and bactericidal function. These techniques use small volumes of blood and are suitable for inclusion in the early screening of individuals who have repeated bacterial infections.

Delivery of genetic screening services.

This paper describes the genetic services in the United Kingdom and how the evolution of genetic screening services is taking place. Since these Community Genetic Services depend on the offer of a screening test that affects the whole population, it is essential that the community is given genetic education and an opportunity to discuss the issues before services are initiated. In this way, the differing beliefs and needs of individual communities are appropriately taken into account. The development of screening services for cystic fibrosis will show whether this community-orientated model can be successful.

A review of experimental models for studying the tissue penetration of antibiotics in man.

Measurement of tissue antibiotic levels is of great importance in developing rational treatment for infection, particularly in patients whose host defense systems are compromised. This review outlines some of the main approaches to this problem, giving examples of the application of the new techniques in different clinical situations.

What do young people think about screening for cystic fibrosis?

We investigated the knowledge of cystic fibrosis and the views about neonatal and carrier screening in 216 school students aged 14 to 16 years. This work was completed before the published identification of the cystic fibrosis gene in September 1989. Although initial knowledge of cystic fibrosis was low (only 17% of the students knew that the disease affected the lungs), there was good recall of basic information about cystic fibrosis and of recessive inheritance after a brief lecture. A total of 86% considered that carrier detection should be offered routinely and 88% felt that an offer of prenatal diagnosis for cystic fibrosis should be made if both prospective parents were known to be carriers. We believe that pilot studies of cystic fibrosis carrier screening in schools should be undertaken.

Severe mental retardation in a boy with partial trisomy 10q and partial monosomy 2q.

A severely mentally subnormal child with many physical stigmata was shown to have the karyotype 46,XY,-2,+der(2),t(2;10)(q31;q24)pat. Full evaluation of this patient's karyotype depended on the family studies. It was shown that a balanced translocation t(2,10) was present in 4 normal males in 3 generations.

Tobramycin therapy of infections due to Pseudomonas aeruginosa in patients with cystic fibrosis: effect of dosage and concentration of antibiotic in sputum.

Established respiratory infections with mucoid Pseudomonas aeruginosa in patients suffering from cystic fibrosis were treated with conventional as well as larger doses of tobramycin. The infection was eradicated in four of the 17 patients treated, but the duration of follow-up study of one patient was short. It appeared that treatment was most successful in those patients in whom the highest peak concentrations of tobramycin in sputum were obtained. No side effects were noted, even when tobramycin was given in large doses for two weeks.