Genetic linkage analysis identifies new proximal and distal flanking markers for the X-linked agammaglobulinemia gene locus, refining its localization in Xq22

Genetic linkage analysis has been instrumental in mapping thegene for X-linked agammaglobulinemia (XLA) to the proximal longarm of the human X chromosome, to Xq22. Due to the relativerarity of this disease the localization of the gene within Xq22has remained imprecise. We have investigated twenty-nine familiesaffected by XLA and have found no recombinants with the DXS178locus in over 30 informative meioses. DXS178 is now the mostreliable and informative locus for use in pre-natal diagnosisand carrier detection of XLA. In addition, we have identifiednew closely linked proximal and distal flanking markers forXLA, DXS442 and DXS101, respectively. These loci are separatedby 2cM, considerably reducing the extent of DNA within whichthe XLA locus can be contained. This will open up the way formore directed positional cloning efforts for the isolation ofthe XLA gene.     

Recurrent Poisoning in Children: A Review

The literature on poisoning accidents or ingestion of toxicsubstances in children is reviewed. Special emphasis is givento the phenomenon of recurrent or repeat episodes. Recommendationsare made concerning means for identifying children who are atrisk for repeat poison episodes, as well as for developing methodsof intervention to prevent such occurrences.     

Identifying amino acid residues that influence plasma clearance of murine IgG1 fragments by site-directed mutagenesis

Site-directed mutagenesis has been used to change amino acid residues of a recombinant Fc-hinge fragment derived from the murine immunoglobulin (Ig)G1 molecule, and the effects of these mutations on the pharmacokinetics of the Fc-hinge fragment have been determined. Specifically, Ile-253, His-310 and Gln-311 of the CH2 domain and His-433 and Asn-434 of the CH3 domain have been changed. In the three dimensional structure of an antibody, these amino acids are in close proximity to each other at the CH2-CH3 domain interface. The mutated Fc-hinge fragments have been purified from recombinant Escherichia coli cells and their pharmacokinetic parameters determined in mice and compared with those of the wild-type Fc-hinge fragment. The results show that the site of the IgG1 molecule that controls the catabolic rate (the ‘catabolic site’) is located at the CH2-CH3 domain interface and overlaps with the Staphylococcal protein A binding site.     

Properties of voltage-gated currents of microglia developed using macrophage colony-stimulating factor

Microglia were isolated from a murine neonatal brain cell culture in which their development had been stimulated by supplementation with the macrophage/microglial growth factor macrophage colony-stimulating factor (M-CSF). Using the whole-cell configuration of the patch-clamp technique, voltage-gated membrane currents were recorded from these microglial cells. Hyperpolarization induced inward rectifying K⁺ currents, as described for microglia from untreated cultures. These currents activated negative to the K⁺ equilibrium potential and, with a strong hyperpolarization, displayed time-dependent inactivation. The inactivation was abolished when extracellular NaCl was replaced by N-methyl-d-glucamine (NMG), thereby indicating a partial block of this K⁺ conductance by Na⁺. Inward rectifying currents were also blocked by extracellularly applied Cs⁺ or Ba²⁺. They were slightly diminished following treatment with extracellular tetraethylammonium chloride (TEA) but were not affected by 4-aminopyridine (4-AP). Upon long lasting depolarizing voltage pulses to potentials positive to 0 mV, the cells exhibited a slowly activating H⁺ current which could be reduced by application of inorganic polyvalent cations (Ba²⁺, Cd²⁺, Co²⁺, La³⁺, Ni²⁺, Zn²⁺) as well as by 4-AP or TEA. Based on their kinetics and pharmacological characteristics, both currents detected on M-CSF-grown microglia are suggested to correspond to the inward rectifier and the H⁺ current of macrophages.     

Mucosal immunization with PLGA-microencapsulated DNA primes a SIV-specific CTL response revealed by boosting with cognate recombinant modified vaccinia virus Ankara

Systemically administered DNA encoding a recombinant human immunodeficiency virus (HIV) derived immunogen effectively primes a cytotoxic T lymphocyte (CTL) response in macaques. In this further pilot study we have evaluated mucosal delivery of DNA as an alternative priming strategy. Plasmid DNA, pTH.HW, encoding a multi-CTL epitope gene, was incorporated into poly(D,L-lactic-co-glycolic acid) microparticles of less than 10 microm in diameter. Five intrarectal immunizations failed to stimulate a circulating vaccine-specific CTL response in 2 Mamu-A*01(+) rhesus macaques. However, 1 week after intradermal immunization with a cognate modified vaccinia virus Ankara vaccine MVA.HW, CTL responses were detected in both animals that persisted until analysis postmortem, 12 weeks after the final boost. In contrast, a weaker and less durable response was seen in an animal vaccinated with the MVA construct alone. Analysis of lymphoid tissues revealed a disseminated CTL response in peripheral and regional lymph nodes but not the spleen of both mucosally primed animals.     

Ultimate tensile strength of dentin: Evidence for a damage mechanics approach to dentin failure

Dentin structure and properties are known to vary with orientation and location. The present study explored the variation in the ultimate tensile strength (UTS) of dentin with location in the tooth. Hourglass specimens were prepared from dentin located in the center, under cusps, and in the cervical regions of human molar teeth. These were tested in tension at various distances from the pulp. Median tensile strengths ranged from 44.4 MPa in the inner dentin near the pulp, to 97.8 MPa near the dentino-enamel junction (DEJ). This increase in the median UTS with distance from the pulp to the DEJ was statistically significant (P <.001). Of particular importance was the observation that the UTS measurements followed a Weibull probability distribution, with a Weibull modulus of about 4.5. The Weibull behavior of the UTS data strongly suggests that the large variances in fracture strength data result from a distribution of preexisting defects in the dentin. These findings justify a damage-mechanics approach to studies of dentin failure.     

Clonal chromosome abnormalities in human breast carcinomas I. Twenty-eight cases with primary disease

Cytogenetic analysis was performed on a selected series of short-term cultures of primary breast carcinomas from 28 patients. All patients had histopathologically confirmed malignancies, with the majority (25/28 cases) demonstrating infiltrating ductal carcinoma. All 28 cases evidenced clonal chromosome abnormalities, with 10/28 displaying only numeric aberrations, whereas 18/28 displayed clonal structural alterations. In near-diploid tumors the most common numeric changes were — 17 and — 19. However, trisomy 7 was the only numeric change in two near-diploid tumors. Structural chromosome alterations were primarily isochromosomes, apparent terminal deletions, and unbalanced non-reciprocal translocations. Chromosomes 1 (10/18–56%) and 6 (8/18–44%) were most frequently altered in this series. Breakpoints of clonal structural abnormalities were shown to cluster to several chromosome segments, including 1p22-q11, 3p11, 6p11–13, 7p11-q11, 8p11-q11, and 19q13. Analysis of the gain or loss of specific chromosome segments revealed that the most consistent tendency was over-representation of 1q, 3q, and 6p. © 1993 Wiley-Liss, Inc.     

The Society for Craniofacial Genetics and Developmental Biology 41st Annual Meeting

The mission of the Society for Craniofacial Genetics and Developmental Biology (SCGDB) is to promote education, research, and communication about normal and abnormal development of the tissues and organs of the head. The SCGDB welcomes as members undergraduate students, graduate students, postdoctoral researchers, medical and dental practitioners, scientists, and academicians who possess an interest in craniofacial biology. Each year our members come together to share their novel findings, build upon, and challenge current knowledge of craniofacial biology.