Cytogenetic diagnosis using midtrimester fetal blood samples: Application to suspected mosaicism and other diagnostic problems

Cytogenetic studies on fetal blood cells obtained at 18–25 weeks gestation have provided information for decision making in 25 cases identified as being at high risk of having an abnormal fetus. In particular, in the 21 cases studied to consider the possibility of true mosaicism, confirmation in fetal blood was obtained in three, one of which presented as a pseudomosaic on the original amniotic fluid cell study. Fetal blood was also informative in two cases (one positive and the other negative) in which a diagnosis of the fragile X syndrome was being considered. Furthermore, when high risk pregnancies presented late in gestation (21–24 weeks), these methods allowed for a rapid cytogenetic diagnosis. The procedure has proved useful in most of these cases since the couples involved had indicated that they would probably have terminated the pregnancy without the reassurance of normal fetal lymphocyte studies. Since the technique carries a much higher risk of pregnancy loss than does amniocentesis, its use should only be considered when there are compelling indications.     

Analysis of human T-cell receptor α-chain cDNAs isolated from peripheral blood mononuclear cells

T-cell receptor α-chain cDNA were generated from unstimulated peripheral blood mononuclear cells of a DR2,3,52a individual using a modified anchor PCR method. Fifty-six cDNA clones were identified representing 47 distinct T-cell receptor clonotypes and 26 VA loci. This analysis identified a new VA gene family VA30, and aew member of the VA6 gene family.     

MECP2 duplication syndrome in a patient from Cameroon

MECP2 duplication syndrome (MDS; OMIM 300260) is an X‐linked neurodevelopmental disorder caused by nonrecurrent duplications of the Xq28 region involving the gene methyl‐CpG‐binding protein 2 (MECP2; OMIM 300005). The core phenotype of affected individuals includes infantile hypotonia, severe intellectual disability, very poor‐to‐absent speech, progressive spasticity, seizures, and recurrent infections. The condition is 100% penetrant in males, with observed variability in phenotypic expression within and between families. Features of MDS in individuals of African descent are not well known. Here, we describe a male patient from Cameroon, with MDS caused by an inherited 610 kb microduplication of Xq28 encompassing the genes MECP2, IRAK1, L1CAM, and SLC6A8. This report supplements the public data on MDS and contributes by highlighting the phenotype of this condition in affected individuals of African descent.     

Proposed methods for the measurement of regional renal blood flow using heat transfer analysis

The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the renal cortex and medulla, and with its nonuniform blood vessel geometries, presents a unique challenge for measuring intrarenal blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate. Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat transfer equations to deduce regional blood flow Research by K.R. Holmes and M.M. Chen was supproted by NIH-NHLBI Grant HL27011, that by T. Adams and S.R. Heisey through the Michigan Heart Association, and that by W.S. Spielman through a grant from the NSF (PCM 8110588) who is a recipient of NIH Research Career Development Award HL01010.     

Cell-free translation of avian erythroblastosis virus RNA yields two specific and distinct proteins with molecular weights of 75,000 and 40,000

Avian erythroblastosis virus (AEV) 28 S virion RNA was translated in vitro in cell-free reticulocyte lysates. Two AEV-specific proteins, one of 75,000 (p75) the other of 40,000 (p40) molecular weight, were detected. p75 is a fusion protein containing gag-specific and AEV-specific peptides. It appears to be translated from the 5′-end of the 28 S AEV RNA and is indistinguishable from the p75 detected in AEV-transformed cells (Hayman et al., 1979). p40 does not share sequences with any viral structural protein. It also contains peptides distinct from those of p75, but one of the five identifiable p40 peptides comigrates with one of the p75 peptides. p40 is translated from a 20 S RNA which contains the 3′-half of the AEV-specific sequences of the genome. These two proteins account for all of the coding capacity of the AEV-specific gene sequences in the 28 S AEV RNA and are candidates for leukemia-specific transforming proteins.     

CD1 assembly and the formation of CD1-antigen complexes

The CD1 antigen presentation system presents lipid antigens to effector T cells, which have diverse roles in antimicrobial responses, antitumor immunity and in regulating the balance between tolerance and autoimmunity. The trafficking of CD1 molecules and lipid antigens facilitates their intersection and binding in specific intracellular compartments. Recent studies have now identified unexpected accessory molecules that are critical to CD1 assembly and lipid loading. The atomic structures of CD1-antigen complexes have defined both the orientation of polar headgroups between the alpha1 and alpha2 helices of CD1 and the manner in which distinct CD1 isoforms bind a range of lipids that have different lengths and numbers of hydrocarbon chains.     

Detection of Rickettsia felis in a New World flea species, Anomiopsyllus nudata (Siphonaptera: Ctenophthalmidae)

The flea and rodent samples studied in this project were collected from field study sites in New Mexico from winter 1998 to spring 2001. During this period, 155 small rodents (14 different species) were live-trapped and combed for the presence of fleas. A total of 253 fleas were collected, comprising 21 species. Two of the 253 fleas collected were polymerase chain reaction (PCR) positive for the Rickettsia 17-kDa protein gene. These two fleas were both Anomiopsyllus nudata Baker, each collected from an individual Neotoma albigula Hartley, on two occasions. Individual fleas positive for the Rickettsia 17-kDa protein gene were then tested with primers targeting the rickettsial genes for citrate synthase (gltA) and two major outer membrane proteins (ompA and ompB). The nucleotide sequences of the PCR products of these two fleas were identical to each other and were 100% (394/394), 100% (1150/1150), 99.8% (469/470), and 99.3% (818/824) similar to the corresponding sequences of the 17-kDa, gltA, ompA, and ompB genes of Rickettsia felis, respectively. Flea homogenates of individual PCR-positive fleas were inoculated into shell vials seeded with Vero cells, and the Gimenez stain technique was used to demonstrate the presence of Rickettsia-like organisms in detached cells found in aspirated medium 19 d after inoculation. These cells were harvested and tested by PCR, targeting portions of the 17-kDa and gltA genes, resulting in products 100% identical to R. felis. This work comprises the first report of R. felis detection in a flea species (A. nudata) endemic to the New World.     

Construction and characterization of Listeria monocytogenes mutants with in-frame deletions in the response regulator genes identified in the genome sequence

Two-component systems are widely distributed in prokaryotes where they control gene expression in response to diverse stimuli. To study the role of the sixteen putative two-component systems of Listeria monocytogenes systematically, in frame deletions were introduced into 15 out of the 16 response regulator genes and the resulting mutants were characterized. With one exception the deletion of the individual response regulator genes has only minor effects on in vitro and in vivo growth of the bacteria. The mutant carrying a deletion in the ortholog of the Bacillus subtilis response regulator gene degU showed a clearly reduced virulence in mice, indicating that DegU is involved in the regulation of virulence-associated genes.     

Speeded right-to-left information transfer: the result of speeded transmission in right-hemisphere axons?

We used the dopaminergic neurotoxicant, 6-hydroxydopamine (6-OHDA), as a tool to characterize the origins of the astrocytic response to injury. Reactive astrocytes were examined by immunocyto- and histo-chemical visualization of nestin protein in the brain and cultivated cells. Following 6-OHDA (dose-dependent) treatment, the expression of nestin-like immunoreactive cells in the corpus callosum and cerebral cortex was increased compared with that of the control animals, indicating that a significant up-regulation of nestin protein occurred in these regions. In the corpus callosum and cerebral cortex, the majority of the nestin-like immunoreactive cells showed a distribution and pattern similar to those of the glial fibrillary acid protein (GFAP)-immunoreactive cells. Double immunofluorescence measurements showed that 100% of the nestin-like immunoreactive cells expressed GFAP-immunoreactive cells, indicating that these nestin-like immunoreactive cells belong to a reactive population of the astrocytes. In this study, we observed the morphological changes in the astrocytes following 6-OHDA administration, demonstrating that 6-OHDA induced injury leads to a rapid and transient up-regulation of nestin-like immunoreactivity in activated astrocytes.