Partial duplication of the short arm of chromosome 2 (dup(2)(p13----p21) associated with mental retardation and an Aarskog-like phenotype

In this report we describe a 3-year-old boy with partial trisomy of the short arm of chromosome 2 due to a de novo tandem duplication 2(dup(2)(p13----p21)). In addition to severe growth retardation and moderate psychomotor delay he presented a dysmorphic syndrome compatible with the clinical diagnostic of Aarskog syndrome.     

Separation and comparison of two monokines with lymphocyte-activating factor activity: IL-1 beta and hybridoma growth factor (HGF). Identification of leukocyte-derived HGF as IL-6

Supernatants of mitogen-stimulated human leukocytes contain two biologically related cytokines, IL-1 and hybridoma growth factor (HGF). IL-1 beta is a potent inducer of HGF in fibroblasts but has little stimulating effect on monocytes that spontaneously produce HGF. Leukocyte-derived HGF and IL-1 were separated by the use of affinity chromatography on specific antibodies and discriminating assay systems for both cytokines. They had different Mr upon gel filtration and SDS-PAGE. In contrast to IL-1 beta, HGF showed heterogeneity on a cation-exchange column. IL-1 beta and HGF were purified to homogeneity by a sequence of four and five purification steps, respectively. Leukocyte-derived HGF was characterized by analysis of its NH2-terminal amino acid sequence. This revealed complete homology with fibroblast-derived HGF, 26-kDa protein, IFN-beta 2, and B cell stimulatory factor 2, molecules which have collectively been designated as IL-6. IL-1 beta exerted an antiviral and growth-promoting effect of fibroblasts, whereas HGF/IL-6 did not. Both IL-1 and IL-6 possessed lymphocyte-activating factor activity, which could be neutralized only by an anti-serum against the corresponding cytokine.     

Heterogeneity of human tissue-type plasminogen activator

Tissue-type plasminogen activator (t-PA) from human melanoma cells (Bowes) was purified by immunosorbent chromatography on affinospecific polyclonal antibodies and gel filtration in the presence of KSCN. The immunosorbent eluate contained three major components of greater than 200, 85 and 65 kDa, respectively. The 65 kDa t-PA component could be separated by gel filtration on Ultrogel AcA44 in the presence of KSCN to a pure preparation yielding a unique N-terminal amino acid sequence. Immunoblot analysis, using affinospecific antibodies against t-PA, was a specific and sensitive method to identify different types of t-PA (I-IV), as well as t-PA-inhibitor complexes and degradation products in unstimulated melanoma cell culture fluids. Furthermore, the t-PA preparations, produced by phorbol ester-treated melanoma cells, were free of type IV and thus differed physiochemically from the constitutively produced t-PA preparations. The composition of t-PA from mammalian cell cultures is thus more complex than hitherto described.     

46,XX/46,XX,del(20)(pter-->p12.2) mosaicism limited to fibroblasts associated with MCA/MR and severe growth deficit.

In this report the authors describe an 8-year-old severely mentally retarded girl with facial features resembling the facial dysmorphism seen in patients with Alagille-Watson syndrome, severe growth retardation and a 46,XX/46,XX,del(20)(pter-->p12.2) mosaicism in fibroblasts.     

Contrasting rates of nucleotide substitution in the X-Linked and Y-Linked zinc finger genes

We have sequenced the entire exon (1,180 bp) encoding the zinc finger domain of the X-linked and Y-linked zinc finger genes (ZFX and ZFY, respectively) in the orangutan, the baboon, the squirrel monkey, and the rat; a total of 9,442 by were sequenced. The ratio of the rates of synonymous substitution in the ZFY and ZFX genes is estimated to be 2.1 in primates. This is close to the ratio of 2.3 estimated from primate ZFY and ZFX intron sequences and supports the view that the male-to-female ratio of mutation rate in humans is considerably higher than 1 but not extremely large. The ratio of synonymous substitution rates in ZFY and ZFX is estimated to be 1.3 in the rat lineage but 4.2 in the mouse lineage. The former is close to the estimate (1.4) from introns. The much higher ratio in the mouse lineage (not statistically significant) might have arisen from relaxation of selective constraints. The synonymous divergence between mouse and rat ZFX is considerably lower than that between mouse and rat autosomal genes, agreeing with previous observations and providing some evidence for stronger selective constraints on synonymous changes in X-linked genes than in autosomal genes. At the protein level ZFX has been highly conserved in all placental mammals studied while ZFY has been well conserved in primates and foxes but has evolved rapidly in mice and rats, possibly due to relaxation of functional constraints as a result of the development of X-inactivation of ZFX in rodents. The long persistence of the ZFY-ZFX gene pair in mammals provides some insight into the process of degeneration of Y-linked genes.Correspondence to: W.-H. Li     

Estimating the intensity of male-driven evolution in rodents by using X-linked and Y-linked Ube 1 genes and pseudogenes

Using sequence data from the last introns of ZFX and ZFY genes, we previously estimated the male-to-female ratio () of mutation rate to be close to 6 in higher primates and 1.8 in rodents. As the mutation rate may vary among different regions of the mammalian genome, it is interesting to see whether sequence data from other regions will give similar estimates. In this study, we have determined the partial genomic sequences of the ubiquitin-activating enzyme El genes (Ube 1x and Ube 1y for the X-linked and Y-linked homologues, respectively) of mice and rats and two mouse Ube 1y pseudogenes. From the intron sequences of the Ube 1 genes, we calculated the divergence of the Y-linked genes (Y = 0.161) and that of the X-linked genes (X = 0.107) between mouse and rat, and found the Y/X ratio to be 1.50. This ratio led to an estimate of = 2.0 with a 95% confidence interval of (1.0, 3.9). Similar estimates of were obtained if mouse Ube 1y pseudogenes were used instead of the mouse Ube 1y functional gene. These estimates are consistent with our previous estimate for rodents and suggest that the sex ratio of mutation rate in rodents is approximately only one-third of that in higher primates. Our estimate of the divergence time between Ube 1x and Ube 1y supports the view that the two genes separated before the eutherian radiation.Correspondence to: W.-H. Li     

Influence of central command and ergoreceptors on the splanchnic circulation during isometric exercise

The splanchnic circulation can make a major contribution to blood flow changes. However, the role of the splanchnic circulation in the reflex adjustments to the blood pressure increase during isometric exercise is not well documented. The central command and the muscle chemoreflex are the two major mechanisms involved in the blood pressure response to isometric exercise. This study aimed to examine the behaviour of the superior mesenteric artery during isometric handgrip (IHG) at 30% maximal voluntary contraction (MVC). The pulsatility index (PI) of the blood velocity waveform of the superior mesenteric artery was taken as the study parameter. A total of ten healthy subjects [mean age, 21.1 (SEM 0.3) years] performed an IHG at 30% MVC for 90 s. At 5 s prior to the end of the exercise, muscle circulation was arrested for 90 s to study the effect of the muscle chemoreflex (post exercise arterial occlusion, PEAO). The IHG at 30% MVC caused a decrease in superior mesenteric artery PI, from 4.84 (SEM 1.57) at control level to 3.90 (SEM 1.07) (P = 0.015). The PI further decreased to 3.17 (SEM 0.70) (P = 0.01) during PEAO. Our results indicated that ergoreceptors may be involved in the superior mesenteric artery vasodilatation during isometric exercise.     

Enzymes of nitrogen metabolism in legume nodules. Purification and properties of NADH-dependent glutamate synthase from lupin nodules.

An NADH-dependent glutamate synthase has been purified 500-fold from the plant cytoplasm fraction of Lupinus angustifolius nodules. It consists of a single polypeptide chain, Mr 235000. The optimum pH is 8.5, at which Km values for 2-oxoglutarate, glutamine and NADH are 39 micrometer, 400 micrometer and 1.3 micrometer respectively. The catalytic centre activity is of the order of 70 s-1 and is independent of pH between 6.5 and 9.5. Glutamate synthase is inhibited by glutamic acid, oxaloacetic acid, aspartic acid and asparagine, all competitive with 2-oxoglutarate; and by NAD+, which is competitive with NADH. There is evidence of two flavine prosthetic groups per enzyme molecule.