Inhibition of deoxynucleoside kinases in human thymocytes prevents dATP accumulation and induction of apoptosis

Thymocytes lacking adenosine deaminase (ADA) activity, a purine metabolism enzyme, accumulate intracellular dATP and consequently undergo apoptosis during development. We have analyzed the effect of ADA enzyme inhibition in human thymocyte suspension cultures with regard to accumulation of intracellular dATP and induction of apoptosis. We demonstrate that while inhibition of deoxycytidine kinase will prevent the accumulation of dATP and induction of apoptosis to a large degree, inhibition of both deoxycytidine kinase and adenosine kinase completely abrogates the accumulation of dATP and significantly reduces the induction of apoptosis. Thus, both deoxynucleoside kinases are involved in this model of ADA deficiency.     

Mutations in LTBP4 Cause a Syndrome of Impaired Pulmonary, Gastrointestinal, Genitourinary, Musculoskeletal, and Dermal Development

We report recessive mutations in the gene for the latent transforming growth factor-β binding protein 4 (LTBP4) in four unrelated patients with a human syndrome disrupting pulmonary, gastrointestinal, urinary, musculoskeletal, craniofacial, and dermal development. All patients had severe respiratory distress, with cystic and atelectatic changes in the lungs complicated by tracheomalacia and diaphragmatic hernia. Three of the four patients died of respiratory failure. Cardiovascular lesions were mild, limited to pulmonary artery stenosis and patent foramen ovale. Gastrointestinal malformations included diverticulosis, enlargement, tortuosity, and stenosis at various levels of the intestinal tract. The urinary tract was affected by diverticulosis and hydronephrosis. Joint laxity and low muscle tone contributed to musculoskeletal problems compounded by postnatal growth delay. Craniofacial features included microretrognathia, flat midface, receding forehead, and wide fontanelles. All patients had cutis laxa. Four of the five identified LTBP4 mutations led to premature termination of translation and destabilization of the LTBP4 mRNA. Impaired synthesis and lack of deposition of LTBP4 into the extracellular matrix (ECM) caused increased transforming growth factor-β (TGF-β) activity in cultured fibroblasts and defective elastic fiber assembly in all tissues affected by the disease. These molecular defects were associated with blocked alveolarization and airway collapse in the lung. Our results show that coupling of TGF-β signaling and ECM assembly is essential for proper development and is achieved in multiple human organ systems by multifunctional proteins such as LTBP4.     

Coupling of cardiac and locomotor rhythms

The pressure within exercising skeletal muscle rises and falls rhythmically during normal human locomotion, the peak pressure reaching levels that intermittently impede blood flow to the exercising muscle. Speculating that a reciprocal relationship between the timing of peak intramuscular and pulsatile arterial pressures should optimize blood flow through muscle and minimize cardiac load, we tested the hypothesis that heart rate becomes entrained with walking and running cadence at some locomotion speeds, by means of electrocardiography and an accelerometer to provide signals reflecting heart rate and cadence, respectively. In 18 of 25 subjects, 1:1 coupling of heart and step rates was present at one or more speeds on a motorized treadmill, generally at moderate to high exercise intensities. To determine how exercise specific this phenomenon is, and to refute the competing hypothesis that coupling is due to vertical accelerations of the heart during locomotion, we had 12 other subjects cycle on an electronically braked bicycle ergometer. Coupling was found between heart rate and pedaling frequency in 10 of them. Cardiac-locomotor coupling appears to be a normal physiological phenomenon, and its identification provides a fresh perspective from which to study endurance.     

Genetic basis for high limonene—cineole content of exceptional Mentha citrata hybrids

Summary Most Mentha species have 1–25% 1-limonene and 0.5–8% 1,8-cineole, but 19 individuals having more than 50% limonene-cineole were found in a progeny of 10,000 Strain 2 M. citrata — M. crispa F ₁ hybrids. When the same strain of M. citrata (2 n = 96) having the genotype I₁I₁ i ₂ i ₂, a lavender herbage odor with oil assaying 30% linalool and 58.5% linalyl acetate, is hybridized with the closely related octoploid species M. aquatica (2 _n = 96) having the genotype i ₁ i ₁ i ₂ i ₂, a menthofuran herbage odor with oil assaying 65–80% menthofuran, the fertile F ₁ hybrids should have the genotype I ₁ i ₁ i ₂ i ₂ and a lavender odor with oil assaying 84–90% linalool — linalyl acetate. In addition to 111 normal lavender-odored hybrids, this cross gave one individual (Strain 38) having 20.4% limonene and 36.4% cineole and one individual (Strain 625) having 67.5% limonene and 23.6% cineole. Since M. aquatica is homozygous for menthofuran production, and since Strain 38 — M. aquatica backcross progenies had the disomic ratio of 1 limonene and cineole-odored: 1 methofuran-odored, it is evident that the 57% limonene — cineole content of Strain 38 is due to a single dominant gene Lm. Strains 38 and 625 were hybridized with other tester species having known genotypes for other oil constituents to demonstrate that the gene Lm prevents the conversion of limonene to more advanced compounds, namely: carvone, pulegone, methofuran, menthone, menthol, and menthyl acetate which are normally developed in the oil of other species having the recessive gene lm. Strain 38 hybrids with M. citrata show that the dominant I gene interrupts oil biogenesis at an earlier stage than the Lm gene and largely prevents the synthesis of limonene and cineole. Nine of 21 strains having 57– 94% limonene — cineole were investigated. Strains 38 and 62 had the genotype i ₁ i ₁ i _{2 i 2} Lm ₁ lm ₁ lm ₂ lm ₂ or i ₁ i ₁ i ₂ i ₂ lm ₁ lm ₁ Lm ₂ lm ₂, whereas Strain 625 and six others had the genotype i ₁ i ₁ i ₂ i ₂ Lm ₁ lm ₁ Lm ₂ 1m ₂. These segregants from the segmental allopolyploids may be explained by assuming that M. aquatica has the genotype and Strain 2 of M. citrata the genotype with A and a designating the non-homologous centromere regions of the two chromosome pairs carrying the linked genes on different chromosome arms. Crossing over between the genes would not be detectible when there is normal autosyndetic bivalent pairing, whereas occasional quadrivalent pairing of the four chromosomes of Strain 2 of M. citrata could lead to gene interchanges between chromosomes non-homologous for the centromere region.Research Assistant, Research Assistant, Senior Chemist, and Director of Plant Research respectively.     

Requirement of Bmp8b for the generation of primordial germ cells in the mouse

In the mouse embryo, the generation of primordial germ cells (PGCs) from the epiblast requires a bone morphogenetic protein-4 (BMP4) signal from the adjacent extraembryonic ectoderm. In this study, we report that Bmp8b, a member of the Gbb-60A class of the BMP superfamily, is expressed in the extraembryonic ectoderm in pregastrula and gastrula stage mouse embryos and is required for PGC generation. A mutation in Bmp8b on a mixed genetic background results in the absence of PGCs in 43% null mutant embryos and severe reduction in PGC number in the remainder. The heterozygotes are unaffected. On a largely C57BL/6 background, Bmp8b null mutants completely lack PGCs, and Bmp8b heterozygotes have a reduced number of PGCs. In addition, Bmp8b homozygous null embryos on both genetic backgrounds have a short allantois, and this organ is missing in some more severe mutants. Since Bmp4 heterozygote embryos have reduced numbers of PGCs, we used a genetic approach to generate double-mutant embryos to study interactions of Bmp8b and Bmp4. Embryos that are double heterozygotes for the Bmp8b and Bmp4 mutations have similar defects in PGC number as Bmp4 heterozygotes, indicating that the effects of the two BMPs are not additive. These findings suggest that BMP4 and BMP8B function as heterodimers and homodimers in PGC specification in the mouse.     

Trisomy 1q43 syndrome: a consistent phenotype with macrocephaly, characteristic face, developmental delay and cardiac anomalies

Trisomy 1q43 syndrome: a consistent phenotype with macrocephaly, characteristic face, developmental delay and cardiac anomalies: Patients with trisomy (1)(q42-qter) present with psychomotor retardation, macrocephaly, occasional presence of facial capillary naevi, cardio-vascular anomalies and small size for gestational age. We report on a girl with the same pattern of malformations, who has pure trisomy 1 q43: duplication of the region (1) (q43) and the translocation of the terminal region of the other chromosome 1 to the derivative 1, narrowing down the critical region for the characteristic traits of severe developmental delay, macrocephaly and congenital cardiac malformations.     

Interspecific variation of body shape and sexual dimorphism in three coexisting species of the genus <Emphasis Type="Italic">Petrotilapia</Emphasis> (Teleostei: Cichlidae) from Lake Malawi

Differences in color patterns have been the most used feature in describing cichlid species belonging to genus Petrotilapia from Lake Malawi. In this study, we quantified morphological variation in body shape within and among three coexisting Petrotilapia species using landmark-based geometric morphometric methods. Statistic analyses revealed significant body shape differences among species but not between sexes. Post hoc multiple comparisons based on Mahalanobis distances revealed that P. nigra was significantly different from P. genalutea and Petrotilapia sp., whereas the latter two were not significantly different. The splines generated showed that the most pronounced variation was in the head region, in which P. nigra had a relatively longer and deeper head than the other two. The most clear-cut distinction was in gape length; P. genalutea had the longest gape, followed by Petrotilapia sp., whereas P. nigra had the shortest gape. Body depth was shallower in P. nigra than the others. When comparing sexes by their centroid size, ANOVA revealed that males were bigger than females. Therefore, we conclude that color is not the only feature that can distinguish these congeners. We discuss the observed sexual dimorphism in terms of sexual selection and relate morphological variation among species to feeding behavior, which may help explain their coexistence in nature.     

Simulation of coronary artery revascularization

Simulation of the commonly constructed geometries of aorto-coronary bypass anastomoses was carried out using especially fabricated distensible tubes and a pulsatile pump. The system pressure was maintained between 80 and 120 mmHg. The total mean flow was set at 250 ml min-1 (Reynolds number of 200) and the pulsatile frequency was varied from 0 to 2 Hz. A water-glycerine mixture having a density and viscosity similar to that of blood was used throughout. A 16 mm film of the front of black dye injected proximal to the anastomosis was made as the dye approached and passed through the anastomosis. Anastomotic geometries consisted of: end to side, parallel, 45 degree angle, and 90 degree angle. Stenoses, located in the tube representing the coronary artery, were simulated using a bevelled insert which represented an 80-85% area reduction. Flow visualization revealed that distensible tubes gave more realistic flow patterns than rigid tubes, a result particularly evident when a stenosis was present. Pulsatile flow demonstrated considerably more mixing than steady flow. The use of pulsatile flow in distensible tubing with a partial stenosis showed retrograde flow through the stenosis which was not evident for either steady flow or for flow in rigid tubing. The flow at the anastomatic site of the graft having an angle of 0 degrees showed a jetting action with a zone of recirculating fluid being present whereas for a 90 degree graft a distinct helical flow was formed distal to the anastomosis.