Sorbitol Gum in Xerostomics: The Effects on Dental Plaque pH and Salivary Flow Rates1

Adequate salivary flow is important for patient comfort and maintenance of oral health. Xerostomia, or dry mouth, is a common clinical complaint. Masticatory and gustatory activity can stimulate salivary flow from functional salivary tissue and the use of sugarless mints and gums have been recommended to individuals who complain of xerostomia, but there are minimum clinical data. A clinical study assessing the effect on salivary flow rates and dental plaque pH of a sorbitol-sweetened chewing gum in subjects with the complaint of xerostomia was conducted. The chewing of the gum in this present study stimulated salivary flow in the subjects with xerostomia. Statistically significant stimulated whole mouth and parotid salivary flow rate increases were found when compared to unstimulated whole mouth and parotid salivary flow rates. Chewing of the sorbitol-sweetened gum also effectively reduced the drop in pH seen following the exposure to a fermentable carbohydrate. The findings of this present study indicate that chewing of a sorbitol-sweetened gum may be of benefit to patients with the complaint of xerostomia.     

Apparent decline in the harbour seal Phoca vitulina population near Hvaler, Norway, following an epizootic

From 1986-90 we tagged 98 harbour seal pups at Hvaler, Norway Fifteen were recovered later the same year of which 10 were recovered in 1988, when the seal population was infected by a morbillivirus The epizootic in 1988 resulted in a population decline of c 75% Predicted birth weight did not vary significantly before and after the epizootic Newborn harbour seals have antibodies against the morbillivirus two years after the outbreak of the disease     

The pH profile for acid-induced elongation of coleoptile and epicotyl sections is consistent with the acid-growth theory

The acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxintreated tissues (4.5–5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5–6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.Abbreviations FS free space - IAA indole-3-acetic acid This research was supported by a grant from the National Adonautics and space Administration (NASA), NAGW 1394 to R.E.C., NASA grant NAGW-297 to M.L.E., and NASA grant NAG 1849 to D.L.R.     

DNA regions associated with the nuclear matrix of Ehrlich ascites cells expose single-stranded sites after deproteinization

Ehrlich ascites cells were pulse-labeled with [3H]thymidine and subjected to prolonged labeling with [14C]thymidine. The isolated nuclei were digested with the restriction endonuclease BspRI and then processed to yield a 'matrix fraction' and a 'non-matrix fraction'. The DNA fragments purified from these fractions and from whole digested nuclei were examined for nitrocellulose-binding sites before and after digestion with single-strand-specific (S1) nuclease. Both, pulse-labeled and long-time-labeled fragments, isolated from the matrix fraction, exhibited a significantly increased content of nitrocellulose-binding sites. The major portion of these sites were rendered non-binding by digestion with single-strand-specific nuclease and consisted most probably of structures exposing relatively small stretches of non-base-paired DNA. The nature of the minor portion of binding sites which was insensitive to single-strand-specific nuclease is not clear. Both types of binding sites are possible candidates for mediating the attachment of DNA to the nuclear matrix.     

Some properties of human and bovine brain cathepsin B

Cathespin B has been purified 750-fold to apparent homogeneity from human and bovine brain cortex using ammonium sulfate fractionation (30–70%), chromatography on Sephadex G-100, CM-Sephadex C-50, and concanavalin A-Sepharose. Enzyme was assayed fluorometrically at pH 4.0 with pyridoxyl-hemoglobin in the presence of 1 mM DTT and 1 mM EDTA. Properties of the enzyme from the two sources proved to be similar. On disc PAGE the purified preparation produced two bands associated with proteinase activity that are due to existence of two multiple forms of brain cathepsin B with pI 6.1 and 6.8. The enzyme is completely inactivated by thiol-blocking reagents, leupeptin, E-64, and demands thiol compounds for its ultimate activity. Z-Phe-Ala-CHN₂ is a potent inhibitor of the enzyme (K _2nd=1280 M⁻¹s⁻¹) in contrast to Z-Phe-Phe-CHN₂ (K _2nd=264 M⁻¹s⁻¹). pH optimum in the reaction of hydrolysis of Pxy-Hb is 4.0–6.0,K _M(app.) =10⁻⁵ M. Cathepsin B splits azocasein: pH optimum 5.0–6.0,K _M(app.)=2.2·10⁻⁵ M, but inclusion of urea in the incubation medium depresses the azocaseinolytic activity of the enzyme 1.5-fold. It does not split Lys-NNap, Arg-NMec and is not inhibited by bestatin. The specific activity of brain cathepsin B with Z-Arg-Arg-NNapOMe at pH 6.0 is 10-fold higher than with Bz-Arg-NNap, Z-Gly-Gly-Arg-NNap is a poor substrate. With Z-Arg-Arg-NMec and Bz-Phe-Val-Arg-NMec the specific acitivity is 80 and 35%, respectively of that with Z-Phe-Arg-NMec. Special Issue dedicated to Dr. Eugene Kreps.     

Self-Renewal Capacity and Clonal Succession of Haemopoietic Stem Cells In Long-Term Bone Marrow Culture

Abstract. The CFU-s proliferative potential varied greatly during long-term cultivation. Most of the CFU-s in the cultures were represented by cells with low renewal capacity. Pre-CFU-s cells capable of producing multipotential colonies in methylcellulose, which contained CFU-s with a high proliferative potential, were identified in the culture. In cultivation of a mixture of cells of different karyotype their ratio changed rapidly from week to week. the findings were consistent with the hypothesis that haemopoietic stem cells are maintained in the culture by the products of a small number of clones which arise and decline in succession, and that pre-CFU-s, but not the CFU-s themselves, are clonogenic progenitors.     

Alzheimer''s paired helical filaments share epitopes with neurofilament side arms.

A panel of monoclonal antibodies to neurofilaments have been investigated with regard to the location of their respective epitopes on neurofilament polypeptides and their ability to label the neurofibrillary tangles and paired helical filaments (PHF) which are characteristic of Alzheimer's disease. All of the neurofilament monoclonal antibodies that label tangles and PHF are directed against epitopes in the side arm domains of the two larger neurofilament polypeptides, NF-H and NF-M, and do not recognise the alpha-helical rod domains of these proteins. Immuno-electron microscopy demonstrates that the neurofilament antibodies label the constituent PHF per se and do not simply stain neurofilaments that might be admixed with PHF. These neurofilament epitopes are differentially retained by PHF, following isolation. Thus, antibody labelling of PHF is not simply due to the presence of normal neurofilament polypeptides. We propose that in tangle-bearing neurons, neurofilaments are degraded by proteases and that it is fragments of the side arms which contribute to the composition of PHF.     

Antagonistic regulation of the glucose/glucose 6-phosphate cycle by insulin and glucagon in cultured hepatocytes.

Flux through the glucose/glucose 6-phosphate cycle in cultured hepatocytes was measured with radiochemical techniques. Utilization of [2-3H]glucose was taken as a measure of glucokinase flux. Liberation of [14C]glucose from [U-14C]glycogen and from [U-14C]lactate, as well as the difference between the utilization of [2-3H]glucose and of [U-14C]glucose, were taken as measures of glucose-6-phosphatase flux. At constant 5 mM-glucose and 2 mM-lactate concentrations insulin increased glucokinase flux by 35%; it decreased glucose-6-phosphatase flux from glycogen by 50%, from lactate by 15% and reverse flux from external glucose by 65%, i.e. overall by 40%. Glucagon had essentially no effect on glucokinase flux; it enhanced glucose-6-phosphatase flux from glycogen by 700%, from lactate by 45% and reverse flux from external glucose by 20%, i.e. overall by 110%. At constant glucose concentrations cellular glucose 6-phosphate concentrations were essentially not altered by insulin, but were increased by glucagon by 230%. In conclusion, under basic conditions without added hormones the glucose/glucose 6-phosphate cycle showed only a minor net glucose uptake, of 0.03 mumol/min per g of hepatocytes; this flux was increased by insulin to a net glucose uptake of 0.21 mumol/min per g and reversed by glucagon to a net glucose release of 0.22 mumol/min per g. Since the glucose 6-phosphate concentrations after hormone treatment did not correlate with the glucose-6-phosphatase flux, it is suggested that the hormones influenced the enzyme activity directly.     

Replicon initiation frequency and intracellular levels of ATP, ADP, AMP and of diadenosine 5',5'-P1,P4-tetraphosphate in ehrlich ascites cells cultured aerobically and anaerobically

When Ehrlich ascites cells were cultured for 2 h under oxygen-free atmosphere, a shut-down of initiation of new replication units was observed by chain length analysis of the nascent daughter strands and by DNA fibre autoradiography. The intracellular level of ATP, ADP and AMP remained virtually normal in the anaerobized cells, while that of diadenosine 5',5'-P1,P4-tetraphosphate was found reduced by about two orders of magnitude. It is proposed that the ceasing of DNA synthesis after O2 removal is at actively controlled regulatory response of the cells in which diadenosine 5',5"'-P1,P4-tetraphosphate is probably involved.     

Metabolism and non-random occurrence of nonnascent short chains in the DNA of Ehrlich ascites cells

The DNA of Ehrlich ascites cells was labeled with radioactive thymidine using different labeling schedules: Incubation periods between 15 s and 4 h; pulse/pulse-chase experiments with pulses in the range of a few minutes; longtime incubation followed by a longtime chase (both in the range of 1 cell generation). From the purified DNA of the labeled cells a fraction (0.3-0.4%) of short chains was separated and partially fractionated by means of a hydroxyapatite thermochromatography procedure. The evaluation of the labelling patterns of the short chains indicated that less than 5% of them can be regarded as replication intermediates ('Okazaki pieces'). The rest, termed nonnascent pieces, exhibited a slow turnover. The life span of the nonnascent pieces was estimated to be about 1 cell generation. On helical DNA, nonnascent pieces were distributed in a non-random manner. Their preferential localisation was nearby sites which caused binding of the DNA, after purification, to nitrocellulose and which occurred about every 60-80 microns on the nuclear DNA of the cells.