Neutral morphogenetic activity of epithelium in heterologous tissue recombinations

To assess the existence of specific and nonspecific epithelial instructions for mesenchymal cell differentiation we compared homospecific and heterospecific mouse and quail tissue recombinations. In heterospecific recombinants between trypsin-dissociated mouse molar mesenchyme and quail epithelia neither odontoblasts nor chondrocytes differentiated. Cartilage appeared if the quail epithelium was contaminated with homologous limb mesenchyme and odontoblasts differentiated if the mouse dental epithelium was contaminated with dental papilla cells.     

Neutral amino acid transport in an androgen-dependent epithelium

• 1.1. Transport of neutral amino acids by the isolated seminal vesicle epithelium of normal and gonadectomized guinea pigs has been investigated by measurement of the uptake of 2-amino[1-¹⁴C]-isobutyric acid and 2-methylamino[1-¹⁴C]isobutyric acid.
• 2.2. The V_max for Na-dependent and -independent transport of both amino acids was reduced by gonadectomy but the general transport characteristics appeared to be unchanged by this treatment.
• 3.3. The most likely explanation of the decreased transport is the loss of transporter molecules associated with the tissue regression that follows rapidly on gonadectomy.

     

Materials as morphogenetic guides in tissue engineering

Within native tissues cells are held within the extracellular matrix (ECM), which has a role in maintaining homeostasis, guiding development and directing regeneration. Efforts in tissue engineering have aimed to mimick the ECM to help guide morphogenesis and tissue repair. Studies have not only looked at ways to mimick the structure and characteristics of the ECM, but have also considered ways to reproduce its molecular properties including its bioadhesive character, proteolytic susceptibility and ability to bind growth factors.     

Kinetics and equilibrium studies on autologous and heterologous recombinations of heavy and light chains of myeloma proteins.

1. The kinetics of the heterologous recombination reaction of alkylated H chains of a myeloma protein (Jo) with alkylated L chains of another myeloma protein (Ita) were studied by following changes with time in the circular dichroism at 235 nm and the results were compared with those for the autologous recombination of Jo-H chains with Jo-H chains reported previously (T. Azuma et al.(1975) J. Biochem. 77, 473-479 and the preceding paper). The heterologous reaction also followed second-order kinetics. The second-order rate constant (kapp) for heterologous recombination was about seven times smaller than that for autologous recombination at pH 5.5, while they were similar between pH 4.2 and 4.7. 2. The apparent association constants (Kapp) for the reaction, H2+L2=H2L2, were determined by measuring the ellipticities at 235 nm of mixtures of H and L chains in various ratios. The values of Kapp for the autologous and heterologous recombinations were both pH-dependent and changed from 10(6) M-1 at pH 3.9 to 108 M-1 at pH 4.3. Using these values of kapp and Kapp, the half-time for the dissociation of autologous H2L2 to H2 and L2 at pH 4.3 was estimated to be 80 hr.     

Neutral alpha-D-mannosidase activity in human granulocytes

The presence of neutral soluble alpha-D-mannosidase activity was shown in human granulocytes. For detection of the enzyme different methods were used: addition of stabilizing agents; sorption of acid alpha-D-mannosidase on concanavalin A-sepharose; inhibition of acid alpha-D-mannosidase; determination of neutral alpha-D-mannosidase in granulocytes of patients with inherited defect of acid alpha-D-mannosidase (mannosidosis). The specific activity of neutral alpha-D-mannosidase in granulocytes of donors calculated in nmol/min/mg of protein was near to the activity in lymphocytes. However the activity in granulocytes calculated in nmol/min/10(8) of cells was approximately 3 times lower than that in lymphocytes. The activity of neutral alpha-D-mannosidase in immature myeloid cells of a patient with chronic myeloid leukaemia was 10 times higher than in natural granulocytes of the same patient. This high activity may be in connection with the process of cell differentiation or the result of malignant transformation.     

Tracking morphogenetic tissue deformations in the early chick embryo

Embryonic epithelia undergo complex deformations (e.g. bending, twisting, folding, and stretching) to form the primitive organs of the early embryo. Tracking fiducial markers on the surfaces of these cellular sheets is a well-established method for estimating morphogenetic quantities such as growth, contraction, and shear. However, not all surface labeling techniques are readily adaptable to conventional imaging modalities and possess different advantages and limitations. Here, we describe two labeling methods and illustrate the utility of each technique. In the first method, hundreds of fluorescent labels are applied simultaneously to the embryo using magnetic iron particles. These labels are then used to quantity 2-D tissue deformations during morphogenesis. In the second method, polystyrene microspheres are used as contrast agents in non-invasive optical coherence tomography (OCT) imaging to track 3-D tissue deformations. These techniques have been successfully implemented in our lab to study the physical mechanisms of early head fold, heart, and brain development, and should be adaptable to a wide range morphogenetic processes.     

Neutral proteinase activity ofCandida albicans

Neutral proteinase activity (pH optimum 6–7.5) was demonstrated in cell extracts of the yeast form ofCandida albicans H-317. Proteolytic activity which required activation by treatment with sodium dodecyl sulfate was measured by a colorimetric assay for Azocoll hydrolysis. The activity was inhibited by antipain, chymostatin, phenylmethylsulfonyl fluoride, andp-chloromercuribenzoate, but was not affected by ethylenediaminetetraacetate, leupeptin, or pepstatin A. These results give the first evidence of a neutral proteinase inC. albicans.     

Delivery of bone morphogenetic proteins for orthopedic tissue regeneration

Carriers for bone morphogenetic proteins (BMPs) are used to increase retention of these factors at orthopedic treatment sites for a sufficient period of time to allow regenerative tissue forming cells to migrate to the area of injury and to proliferate and differentiate. Carriers can also serve as a matrix for cell infiltration while maintaining the volume in which repair tissue can form. Carriers have to be biocompatible and are often required to be bioresorbable. Carriers also have to be easily, and cost-effectively, manufactured for large-scale production, conveniently sterilized and have appropriate storage requirements and stability. All of these processes have to be approvable by regulatory agencies. The four major categories of BMP carrier materials include natural polymers, inorganic materials, synthetic polymers, composites of these materials. Autograft or allograft carriers have also used. Carrier configurations range from simple depot delivery systems to more complex systems mimicking the extracellular matrix structure and function. Bone regenerative carriers include depot delivery systems for fracture repair, three-dimensional polymer or ceramic composites for segmental repairs and spine fusion and metal or metal/ceramic composites for augmenting implant integration. Tendon/ligament regenerative carriers range from depot delivery systems to three-dimensional carriers that are either randomly oriented or linearly oriented to improve regenerative tissue alignment. Cartilage regenerative systems generally require three-dimensional matrices and often incorporate cells in addition to factors to augment the repair. Alternative BMP delivery systems include viral vectors, genetically altered cells, conjugated factors and small molecules.     

Group representation of genetic recombinations

An algebraic representation of operations of genetic recombinations is illustrated. It is shown that the recombinations between chromosomes in the two-strand model can be represented by groups, in the sense of the theory of groups. Recombinations between chromosomes with inversions and a translocation are considered as well as cases without them. It is found that the groups derived from such cases are Abelianp-groups (p=2) and that the types of the Abelian groups for the various pairs of chromosomes are different from each other. Differences among those recombination groups are illustrated by showing the sets of generators of the various groups, which generate the corresponding recombination groups by multiplication.