Development of trigeminal mesencephalic and motor nuclei in relation to masseter muscle innervation in mice.

This study evaluated temporospatial changes in the central organization of trigeminal mesencephalic (mesV) and motor (motV) nuclei during their development. Very little is known regarding the timing of formation of these trigeminal nuclei and the role that target tissue interactions may have on their spatial organization. Cells located in motV innervate muscles of mastication while the mesV nucleus contains populations of primary afferent cells that innervate muscle spindles in jaw closing muscles and periodontal mechanoreceptors around the roots of teeth. To label mesV afferents and motV efferents during their development, lipophilic dyes, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) or 4-(4-dihexadecylamino)styryl)-N-methylpyridinium iodide (DiA), were inserted into various jaw muscles, the dorsomedial mesencephalic region or tooth buds of maxillary or mandibular teeth of embryonic or postnatal mouse pups. Parasagittal sections were evaluated under epifluorescence to determine the temporospatial organization of trigeminal nuclei and the timing of outgrowth of their processes to target tissues. Early in development, motV motoneurons were organized in columns or clusters closely associated with groups of motoneuron axon fascicles that innervated a specific muscle. Double labelling of masseter and temporalis muscles showed that the columns containing motoneurons associated with these muscles were interdigitated early in development but later condensed into respective motoneuron pools. In contrast, no spatial organization of mesV afferent cell bodies was observed throughout the developmental sequence examined. The results of this study also demonstrated that motV processes enter into jaw muscle at least 1 day prior to proprioceptive afferents. MesV afferent appearance at the tooth was further delayed by 10 days suggesting different signaling mechanisms for these two targets.

Clinical evaluation of bacterial leakage of endodontic temporary filling materials.

This study was an in vivo comparison of the bacterial leakage associated with three endodontic temporary restorative materials: Cavit, Intermediate Restorative Material (IRM), and TERM. The access openings of 51 endodontically treated teeth were randomly sealed with a 4-mm thickness of one of the three materials. Three wk after placement of each temporary restoration, bacterial leakage was evaluated by sampling from beneath the temporary restoration and then culturing the samples both aerobically and anaerobically. Positive growth occurred in 4 of 14 TERM samples and in 1 of 18 IRM samples. Cavit did not demonstrate leakage in any of the teeth in which it was used. Cavit provided a significantly better seal than TERM over the study period.

Diabetic BB/Wor rat haptoglobin exhibits a probable structural abnormality in Asn-linked oligosaccharides.

In this study we demonstrate that haptoglobin, a serum glycoprotein secreted by the liver, has altered structure in the BB/Wor diabetic rat. SDS-PAGE of haptoglobin (a tetramer composed of two glycosylated beta-chains each containing two sites for Asn-linked oligosaccharides connected by disulfide bonds with two nonglycosylated alpha-chains) clearly shows that the beta-chain of haptoglobin from diabetic rats is smaller than normal, with a molecular mass of 39 instead of 40 kDa. Both acute and chronic diabetic rats exhibit the defect. Defective haptoglobin appears in the serum within 4 days of onset of the disease, but insulin therapy prevents the defect. Removal of Asn-linked oligosaccharides with peptide: N-glycosidase F from Flavobacterium meningosepticum abolished the size difference between the beta-chains from normal and diabetic haptoglobin, with the molecular mass in both cases shifting to 30 kDa. Haptoglobin from both normal and diabetic rats was resistant to digestion by endoglycosidase H from Streptomyces griseus, which cleaves high mannose-type chains. Removal of sialic acid with neuraminidase treatment resulted in a reduction in the molecular mass in both cases, but without eliminating the size difference between the two. These results demonstrate that haptoglobin from diabetic BB/Wor rats contains a structural abnormality which correlates with onset of the disease. The defect is most likely due to an alteration in Asn-linked oligosaccharides, probably involving a change in the neutral sugars of complex-type oligosaccharide chains. This finding represents the first example of an altered Asn-linked oligosaccharides in diabetes.

Effects of glucose starvation and puromycin treatment on lipid-linked oligosaccharide precursors and biosynthetic enzymes in Chinese hamster ovary cells in vivo and in vitro.

Previous studies from several laboratories have demonstrated that glucose-starved Chinese hamster ovary (CHO) cells and other cells in culture switch from synthesis of the normal Glc3Man9GlcNAc2-P-P-Dol to Man5-GlcNAc2-P-P-Dol. In this study we have investigated this phenomenon in CHO cells in vitro and in vivo in order to determine the possible site of this block. Our results demonstrate that enzymatic activities responsible for Man9GlcNA2 synthesis in vitro are normal in glucose-starved cells. In vivo, however, the pool of GDP-[3H]Man is severely depleted, while [3H]mannose incorporation into lipid-linked and protein-bound Man5GlcNAc2 is increased. This result suggests that the available GDP-Man in starved cells is utilized to synthesize Man5GlcNAc2 preferentially, resulting in a reduction of Dol-P-Man and Man6-Man9 GlcNAc2 synthesis in vivo in glucose-starved cells. Conditions which prevent the depletion of GDP-[3H]Man in glucose-starved cells, such as puromycin or cycloheximide treatment, result in normal synthesis of Man9GlcNAc2 by glucose-starved cells. An unexpected finding in the course of this study is that puromycin or cycloheximide treatment of cells, which is known to inhibit lipid-linked oligosaccharide synthesis in glucose-fed cells, has no such inhibitory effect on glucose-starved cells.

Resection arthrodesis of the knee for sarcoma: preliminary results.

The surgical removal of malignant bone tumors of the knee requires the generous removal of large segments of femur and tibia with large cuffs of surrounding musculature. This type of resection does not leave the necessary muscles and soft tissue for a functioning knee joint, either through the use of a large custom-made total knee replacement or a large cadaver homograft. Arthrodesis of the knee with an intramedullary rod and segmental bone grafting is a method to reconstruct the large defects remaining after this type of resective surgery. The technique may also have good application in the salvage of failed total knee replacements. Fifteen patients have undergone resection of sarcomas in the bones of the knee area followed by reconstruction with an intramedullary rod and grafting of the gap left by the resected sarcoma. Tumor has been controlled locally in all but one case, which involved prior contamination before our treatment of the patient. Twenty-six of the 28 segmental grafts, which averaged 21.6 cm, have gone to primary bone union. There have been two infections, two fractures-one of the graft and one of the donor site-and two patients with excessive shortening of the grafted segment. The limiting factor in the length of the resection possible is the narrow diameter at the isthmus of the femur and length of the fibular graft available. Updated techniques have decreased the incidence of surgical complications. It appears from this study and experimental studies that large autografts will heal in the face of preoperative and postoperative Adriamycin chemotherapy. It is our conclusion that resection arthrodesis of the knee is a functional reconstructive method for patients requiring extensive resection of sarcoma of the mid to distal femur and proximal tibia.