Crystalline structure and packing of mannan I

The x-ray fiber diffraction pattern of the mannan I polymorph has been reexamined using the linked atom least squares (LALS) model-building program. The chain conformation and packing were refined using atomic coordinates derived from the x-ray crystallographic structure of mannotriose. The study confirmed the conclusions of previous investigations and showed that, in mannan I, the chains are antiparallel. Mannan polymorphism is compared with other related polysaccharides and the biological significance of this result in relation to the biosynthesis of mannan is discussed.     

Cytoskeletal integration in a highly ordered sensory epithelium in the organ of Corti: reponse to loss of cell partners in the Bronx waltzer mouse

This report is concerned with control of cell shaping, positioning, and cytoskeletal integration in a highly ordered cochlear neuroepithelium. It is largely based on investigations of events that occur during abnormal morphogenesis of the organ of Corti in the Bronx waltzer (bv/bv) mutant mouse. The organ's sensory hair cells and adjacent supporting cells ordinarily construct a spatially elaborate and supracellularly integrated cytoskeletal framework. Large microtubule bundles are connected to cytoskeletal components in neighbouring cells by actin-containing meshworks that link them to substantial arrays of adherens junctions. In bv/bv mice, degeneration and loss of most inner hair cells and outer pillar cells occurs during organ development. These cells flank each side of a row of inner pillar cells that respond by upregulating assembly of their actin-containing meshworks. This only occurs in surface regions where they no longer contact cell types involved in construction of the cytoskeletal framework. The meshworks are larger and exhibit a more extensive sub-surface deployment than is normally the case. Hence, assembly of intercellular cytoskeletal connecting components can proceed without contact with appropriate cell neighbours but termination of assembly is apparently subject to a negative feedback control triggered by successful completion of intercellular connection with the correct cell neighbours. In addition, inner pillar cells compensate for loss of cell neighbours by interdigitating and overlapping each other more extensively than is usually the case to increase opportunities for generating adherens junctions. Certain adherens junctions in the organs of +/+ and bv/bv mice exhibit features that distinguish them from all previously described cell junctions. The dense plaques on their cytoplasmic faces are composed of aligned ridges. We suggest that they are called ribbed adherens junctions. Perturbations of cell shaping and positioning indicate that loss of inner hair cells is the primary consequence of the bv mutation. Most of the other abnormalities can be understood in terms of a secondary sequence of morphogenetic aberrations (precipitated by loss of inner hair cells). These aberrations provide new information about the ways in which supporting cells help to control hair cell positioning.     

Epithelial induction of stromal tenascin in the mouse mammary gland: from embryogenesis to carcinogenesis

The distribution of the extracellular matrix glycoprotein tenascin was studied by immunofluorescence in the developmental history of the mouse mammary gland from embryogenesis to carcinogenesis. Tenascin appeared only in the mesenchyme immediately surrounding the epithelia just starting morphogenesis, that is, in embryonic mammary glands from 13th to 16th day of gestation, in mammary endbuds which are a characteristic structure starting development during maturation of the mammary gland, and in the stroma of malignant mammary tumors. However, tenascin was absent in the elongating ducts of embryonic, adult, proliferating, and involuting mammary glands and preneoplastic hyperplastic alveolar nodules. The transplantation of embryonic submandibular mesenchyme into adult mammary glands induces the development of duct-alveolus nodules, which morphologically resemble developing endbuds. Tenascin reappeared around those nodules during the initial stages of their development. Tenascin expression could be induced experimentally in several ways. First, tenascin was detected at the site where the first mammary tumor cells GMT-L metastasized. Second, tenascin was detected in the connective tissue in the tumors derived from the injected C3H mammary tumor cell line CMT315 into Balb/c nude mouse. Cross-strain marker anti-CSA antiserum clearly showed that the tenascin-positive fibroblasts were of Balb/c origin. Third, when embryonic mammary epithelium was explanted on to embryonic mammary fat pad cultures, the mesenchymal cells condensed immediately surrounding the epithelium. Tenascin was detected in these condensed cells. From these three observations we conclude that both embryonic and neoplastic epithelium induced tenascin synthesis in their surrounding mesenchyme.     

Defensive strategies in planktonic coelenterates

Some planktonic coelenterates respond to potentially harmful stimulation by protective involution, others by escape behaviour. Examples of protective involution are seen in the ‘crumpling’ behaviour of various hydrome‐dusae (Sarsia, Euphysa) and of siphonophores such as Hippopodius. Involution may be accompanied by striking visual displays e.g. light emission in Euphysa, light emission and blanching in Hippopodius. These displays probably serve to startle or blind interlopers. In Hippopodius, light emission in the dark would have the same effect as blanching in the light, an example of behavioural self‐mimicry.

Animals employing escape locomotion include the ctenophore Euplokamis, the siphonophore Nanomia and the rhopalonematid medusa Aglantha. All of these forms have evolved giant axons that facilitate escape by reducing response time. The central nervous circuitry underlying locomotion in Aglantha is reviewed.

In a few cases (e.g. Aglantha and possibly Nanomia), the responses described can be seen as defensive against predators, but in the majority of cases, the responses probably serve primarily to reduce the risk of damage due to accidental contact with other organisms.     

Structural investigation of Klebsiella serotype K32 polysaccharide

The capsular polysaccharide from Klebsiella K32 has been studied by using methylation, periodate oxidation, and partial-hydrolysis techniques. The polysaccharide is shown to comprise the four-sugar repeating unit below. Features of interest in this structure include the presence of a β-linked l-rhamnosyl residue, and the extreme lability of the 1-carboxyethylidene acetal towards acid. N.m.r. spectroscopy was used extensively to establish the nature of the anomeric linkages and to identify oligosaccharides obtained by the various degradative techniques used.     

A method for the epidemiologic study of early diabetes

A diabetic survey was conducted among 4048 subjects well enough to report for work, using a questionnaire covering past, present, family and obstetric history, and a capillary blood glucose determination at least 1½ hours after eating. A “positive screen” was obtained in 267 individuals, in 67 on the basis of elevated blood glucose value alone, in 179 on the basis of questionnaire responses alone, and in 21 by both criteria. Glucose tolerance tests were performed on 130 subjects (49% of eligible individuals) and yielded diabetic curves in 18, 6 and 33% respectively for the three categories of positive screening tests.It is suggested that the magnitude of the group with positive history only is such that future natural history studies must take this subsample into consideration.