Definitive surgical correction of vertical maxillary deficiency

Inferior repositioning of the maxilla to correct vertical maxillary deficiency has been associated with variable degrees of instability and subsequent relapse. Resorption of bone-graft material has been incriminated as the primary cause of postoperative instability. This paper reports on nine patients who have undergone inferior maxillary repositioning resulting in no residual bone contact between the down-fractured maxilla and superior midface. Mean inferior maxillary repositioning was 6.2 mm. Osteotomy gaps were implanted with porous block hydroxyapatite (Interpore 200), and maxillae were rigidly fixed in position with miniplates. No postoperative intermaxillary fixation was utilized in any patient. Follow-up ranged from 11 to 28 months, with a mean of 19.6 months. Cephalometric analyses at follow-up revealed excellent stability of the repositioned maxillae, with a mean vertical relapse of 4.3 percent. No complications were associated with this procedure. The biomechanical rationale contributing to the success of this operative technique is discussed.     

Embryonic Sources of Definitive Hemopoietic Stem Cells

A review of one of the key problems of experimental hematology: the origin of hemopoietic stem cells in the development of vertebrates (amphibians, birds, and mammals). The appearance and functioning of two independent sources of hemopoietic stem cells (extra- and intraembryonic) were considered in amphibians, birds, and mammals. The contribution of each source to the formation of definitive hemopoietic tissue was analyzed. It was shown for amphibians and birds that intraembryonic organs such as the dorsolateral plate and the mesenchyme of dorsal aorta are involved in the formation of adult hemopoietic tissue, while the extraembryonic organs such as ventral islets and the yolk sac are devoid of true stem cells and provide only for the primary, transient hemopoiesis. New data have been considered concerning the previously unknown intraembryonic hemopoietic organ in mammals, a region of aorta–gonad–mesonephros arising in embryogenesis simultaneously with the yolk sac. Two extreme views on the involvement of stem cells of all these organs in the formation of definitive hemopoiesis have been considered. The data are provided on the interaction of the embryonic hemopoietic stem cells and the hemopoietic microenvironment of adult recipients.     

Definitive hematopoiesis requires the mixed-lineage leukemia gene

The Mixed-Lineage Leukemia (MLL) gene encodes a Trithorax-related chromatin-modifying protooncogene that positively regulates Hox genes. In addition to their well-characterized roles in axial patterning, Trithorax and Polycomb family proteins perform less-understood functions in vertebrate hematopoiesis. To define the role of MLL in the development of the hematopoietic system, we examined the potential of cells lacking MLL. Mll-deficient cells could not develop into lymphocytes in adult RAG-2 chimeric animals. Similarly, in vitro differentiation of B cells required MLL. In chimeric embryos, Mll-deficient cells failed to contribute to fetal liver hematopoietic stem cell/progenitor populations. Moreover, we show that aorta-gonad-mesonephros (AGM) cells from Mll-deficient embryos lacked hematopoietic stem cell (HSC) activity despite their ability to generate hematopoietic progeny in vitro. These results demonstrate an intrinsic requirement for MLL in definitive hematopoiesis, where it is essential for the generation of HSCs in the embryo.     

Definitive characterization of human thymine glycol N-glycosylase activity

An N-glycosylase activity that released cis-[3H]-5,6-dihydroxy-5,6-dihydrothymine (thymine glycol, TG) from chemically oxidized poly(dA-[3H]dT) was unambiguously characterized both in extracts of HeLa cells and in purified Escherichia coli endonuclease III. This was accomplished by use of microderivatization procedure that quantitatively converted cis-TG to 5-hydroxy-5-methylhydantoin (HMH). The reaction products were analyzed by high-pressure liquid chromatography before and after derivatization by using cis-[14C]TG and [14C]HMH, which had been independently synthesized, as reference compounds. This technique facilitated construction of a v/[E]t plot for the enzyme activity in HeLa cells, permitting estimation of its specific activity. The results obtained prove the existence of both human and bacterial N-glycosylase activities that effect removal of TG from DNA.     

Definitive diagnosis of breast implant rupture by ultrasonography

Silicone breast implantation is entering its fourth decade. Our ability to monitor the integrity of "old" prostheses is questioned. Clinical and mammographic examinations are reliable indicators of implant rupture only if there has been gel migration away from the implant pocket. Ultrasonography is presented as a reliable, sensitive method of evaluation of implant integrity. It should be considered the definitive study of prosthesis integrity. When sonography is added to mammographic and clinical examination, the preoperative evaluation of symptomatic augmented breasts is complete. Ultrasonography may be considered with mammography in the routine breast examination of all previously augmented patients.     

Definitive identification of Bacillus anthracis—a review

The word 'problem' is seen with some frequency in relation to clear differentiation between Bacillus anthracis and B. cereus. In fact, although the close relationship of these two species is undisputed, it is only in the case of a few borderline isolates, rarely encountered in practice, that any sort of identification problem exists. Until recently this was only important to the taxonomist who found it unsatisfactory not to be able to identify definitively such isolates. To most others, if the isolate was unable to produce anthrax in a laboratory animal, it was discarded as irrelevant without being named, or it was called B. cereus or given a name such as B. anthracis similis, or even a totally unrelated name. More recently, in view of the new light in which B. anthracis is increasingly seen, resulting from its putative association with bioaggression, clear identification has become a more critical issue. This paper reviews the current state of the art and suggests the way forward for the future.     

Definitive repair of the unilateral cleft lip nasal deformity

The majority of patients with a unilateral cleft nasal deformity still benefit from additional nasal surgery in their teenage years, despite having undergone a primary nasal repair. However, the secondary nasal deformity of these patients stands in sharp contrast to those of children who have not benefited from primary repair. The authors' algorithm for the definitive correction of these secondary deformities considers the differences in these two patient groups and defines their indications for rib cartilage grafts and their method of using septal and ear cartilage in the repair. Balancing the muscle forces on the septum and alar cartilage is emphasized in both the primary and secondary repair. Both cartilage malposition and hypoplasia of the lower lateral cartilage complex have been identified as factors contributing to the deformity.     

Definitive assumption of heart function by the artificial heart

Reproducing the function of the natural heart with an artificial heart requires a multi-disciplinary approach. Problems to be solved are anatomical, physiological, biological and technical ones. Moreover, clinical use of the artificial heart on a large scale in the near future may involve economical, ethical and legal issues. These several aspects are reviewed, and the State of the Art in 1981 is established.     

Definitive Evidence for the existence of tight junctions in invertebrates

Extensive and unequivocal tight junctions are here reported between the lateral borders of the cellular layer that circumscribes the arachnid (spider) central nervous system. This account details the features of these structures, which form a beltlike reticulum that is more complex than the simple linear tight junctions hitherto found in invertebrate tissues and which bear many of the characteristics of vertebrate zonulae occludentes. We also provide evidence that these junctions form the basis of a permeability barrier to exogenous compounds. In thin sections, the tight junctions are identifiable as punctate points of membrane apposition; they are seen to exclude the stain and appear as election- lucent moniliform strands along the lines of membrane fusion in en face views of uranyl-calcium-treated tissues. In freeze-fracture replicas, the regions of close membrane apposition exhibit P-face (PF) ridges and complementary E-face (EF) furrows that are coincident across face transitions, although slightly offset with respect to one another. The free inward diffusion of both ionic and colloidal lanthanum is inhibited by these punctate tight junctions so that they appear to form the basis of a circumferential blood-brain barrier. These results support the contention that tight junctions exist in the tissues of the invertebrata in spite of earlier suggestions that (a) they are unique to vertebrates and (b) septate junctions are the equivalent invertebrate occluding structure. The component tight junctional 8- to 10-nm-particulate PF ridges are intimately intercalated with, but clearly distinct from, inverted gap junctions possessing the 13-nm EF particles typical of arthropods. Hence, no confusion can occur as to which particles belong to each of the two junctional types, as commonly happens with vertebrate tissues, especially in the analysis of developing junctions. Indeed, their coexistance in this way supports the idea, over which there has been some controversy, that the intramembrane particles making up these two junctional types must be quite distinct entities rather than products of a common precursor.     

Definitive prenatal diagnosis for type III glycogen storage disease.

Prenatal diagnosis for type III glycogen storage disease was performed by using (1) immunoblot analysis with a polyclonal antibody prepared against purified porcine-muscle debranching enzyme and (2) a qualitative assay for debranching-enzyme activity. Cultured amniotic fluid cells from three pregnancies (three families in which the proband had absence of debrancher protein) were subjected to immunoblot analysis. Two unaffected and one affected fetus were predicted. In addition, cultured amniotic fluid cells from nine pregnancies (eight families) were screened with a qualitative assay based on the persistence of a polysaccharide that has a structure approaching that of a phosphorylase limit dextrin when the cells were exposed to a glucose-free medium. This qualitative assay predicted six unaffected and three affected fetuses. All predictions by either method were confirmed postnatally except for one spontaneously aborted fetus. Our data indicate that a definitive diagnosis of type III glycogen storage disease can be made prenatally by these methods.