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Biomedical subjects

K Schenck

Publications and source records attributed to K Schenck.

At least 19 recordsLinked to original sources
PubMed1995

Deletion of a C-terminal sequence of the class II-associated invariant chain abrogates invariant chains oligomer formation and class II antigen presentation.

The MHC class II-associated invariant chain (Ii) is involved in Ag processing and presentation. Physical association of MHC class II molecules with Ii and an effect of Ii on peptide loading to class II have been demonstrated, but to date these functions have not been related to a particular region of Ii. We investigated luminal deletion mutants of Ii and their role in Ag processing and presentation. IAk-expressing L cells were transfected with deletion mutants of the Ii gene and assayed for their ability to present hen egg lysozyme to three different T cell hybridomas. It is shown that the sequence aa 131-191 of Ii is important for the presentation of native hen egg lysozyme. In addition, this C terminal region is shown to be responsible for Ii oligomer formation. It is therefore conceivable that oligomer formation of Ii is a prerequisite for class II-restricted Ag processing and presentation.

Animals↗
PubMed1995

High numbers of T cells in gingiva from patients with human immunodeficiency virus (HIV) infection.

A quantitative, immunohistologic evaluation of CD3+, CD4+ and CD8+ cells was carried out on gingival biopsies from 25 HIV-infected persons with gingivitis or periodontitis and 13 HIV-seronegative persons with periodontitis. CD3+ T cells were found in all biopsies. CD8+ cells were significantly more numerous and the CD4+/CD8+ ratio was significantly decreased in the gingival connective tissue of the HIV+ patients (p < 0.05). The number of CD4+ lymphocytes subjacent to the pocket epithelium was moderately lower in the HIV+ patients as compared to the HIV patients (p < 0.05). HIV+ patients with a history of necrotizing periodontal disease had fewer CD4+ cells subjacent to the oral gingival epithelium than patients without such disease (p < 0.05). The general HIV-related changes in T lymphocyte numbers were therefore reflected in inflamed gingival tissues. HIV+ patients had, however, significantly higher CD4+/CD8+ ratios in gingiva than in peripheral blood (p < 0.05), indicating that CD4+ T cells are actively recruited to gingiva, even in cases of extreme CD4+ T lymphocytopenia.

Adult↗
PubMed1994

Serotonin-induced contraction in canine coronary artery and saphenous vein: role of a 5-HT1D-like receptor.

The identity of the serotonin (5-HT) receptor(s) that mediate(s) contraction in canine coronary artery and saphenous vein remains controversial. Ring segments of endothelium-denuded coronary artery and helical strips of saphenous vein were suspended in organ chambers for measurement of isometric force. 5-HT, alpha Me-5-HT and sumatriptan contracted both coronary artery and saphenous vein and the non-selective 5-HT receptor antagonist 1-naphthylpiperazine (100nM) blocked 5-HT- and sumatriptan-induced contraction in both tissues. The agonist rank order potency for contraction (5-HT > sumatriptan > alpha Me5-HT > 5-MeOT > 5-MeT) was similar in both tissues and was consistent with that for a 5-HT1D receptor. Oligonucleotide primers specific for the 5-HT1D receptor sequence were designed for use in a polymerase chain reaction (PCR). cDNA derived from total RNA or mRNA from canine tissues was used in the PCR. PCR resulted in the amplification of a 632 base pair sequence in both canine coronary artery and saphenous vein; consistent with that expected for the 5-HT1D receptor. Southern blot analysis, with an oligonucleotide probe internal to the sequence amplified by the PCR primers, confirmed that the sequence amplified by PCR was the 5-HT1D receptor. Thus, the 5-HT1D receptor is expressed in canine coronary artery and saphenous vein and taken together with the pharmacological data, supports the possibility that a 5-HT1D-like receptor mediates contraction in these two tissues.

5-Methoxytryptamine↗
PubMed1994

Relationship between 5-HT2A receptor mRNA density and contractility in trachea and aorta from guinea pig and rat.

The present studies document marked differences in contractile responsiveness to serotonin in trachea and aorta between guinea pig and rat. For example, the guinea pig trachea and rat aorta markedly contract in response to serotonin via activation of 5-HT2A receptors. In contrast, the rat trachea and guinea pig aorta only modestly contract to serotonin. The availability of 5-HT2A receptor selective cDNA clones from brain of both guinea pig and rat permitted molecular probes to be designed and PCR amplification studies initiated to identify and quantify 5-HT2A receptor specific mRNA in these tissues. For trachea, 3-fold higher concentrations of 5-HT2A receptor specific mRNA were found in guinea pig relative to rat trachea. These data are consistent with the more profound contractile response to serotonin in guinea pig versus rat trachea and suggest that differences in tracheal contractility to serotonin correlate with the density of 5-HT2A receptor mRNA. In contrast, although rat aorta contracted more dramatically to serotonin than guinea pig aorta, rat aorta possessed a similar concentration of 5-HT2A receptor specific mRNA as compared to guinea pig aorta. Thus, for the aorta, differences in the concentration of 5-HT2A receptor mRNA are not sufficient to explain the observed differences in contractility between tissues from guinea pig and rat. These studies documenting 5-HT2A receptor mRNA in rat trachea and guinea pig aorta, two tissues that do not markedly contract in response to serotonin indicate that 5-HT2A receptor mRNA although present, has not resulted in a receptor capable of mediating a contractile response in these tissues.

Animals↗
PubMed1994

Heat shock response in Actinobacillus actinomycetemcomitans.

The heat shock response in Actinobacillus actinomycetemcomitans, a capnophilic Gram-negative bacterial species that is implicated in the development of certain forms of periodontitis, was characterized. Different strains of A. actinomycetemcomitans were grown at 37, 42 and 48 degrees C in the presence of 35S-methionine. The bacterial cells were lysed, run on SDS-PAGE and subsequently blotted on nitrocellulose paper. After autoradiography of the blots, several protein bands from the cultures at 42 degrees C showed an increased intensity; major bands were observed at 90, 70, and 60 kDa, but increased protein synthesis was also detected at 54, 28 and 17 kDa. Nitrocellulose blots were also incubated with a panel of monoclonal and polyclonal antibodies directed to epitopes on different heat shock proteins. Strong reactivity was found with several antibodies at the position corresponding to a molecular mass of 60 kDa. The protein is probably the GroEL homologue in A. actinomycetemcomitans, a member of the 'common bacterial antigen' family.

Aggregatibacter actinomycetemcomitans↗
PubMed1994

Candidal infection of the gingiva in HIV-infected persons.

Gingival biopsies were taken from 27 HIV (human immunodeficiency virus)-seropositive persons with gingivitis or periodontitis and 16 HIV-seronegative persons with periodontitis. Sections were stained with hematoxylin and eosin or periodic acid-Schiff. Candidal hyphae and pseudohyphae were found in the parakeratinized oral epithelium in 7 specimens from the HIV-infected patient group such specimen. No fungal invasion was found in any of the biopsies from the HIV-seronegative persons. Candidal invasion was significantly more frequent (P < 0.05) in patients with a confirmed history of necrotizing periodontal diseases (5/9) than in patients without known episodes of such diseases (3/18). The most prominent histopathologic changes observed in connection with candidal invasion comprised polymorphonuclear leucocyte infiltration of the oral gingival epithelium and numerous mitoses, some of which were located suprabasally. It is suggested that Candida albicans may contribute to the development of necrotizing periodontal diseases in HIV-infected persons.

AIDS-Related Opportunistic Infections↗
PubMed1993

The segment of invariant chain that is critical for association with major histocompatibility complex class II molecules contains the sequence of a peptide eluted from class II polypeptides.

Major histocompatibility complex class II molecules present peptides from an extracellular source of antigens to CD4+ T lymphocytes. The class II-associated invariant chain affects this role of alpha and beta polypeptides by restriction of peptide loading to endocytic vesicles. Up to now no specific portion of the invariant chain has been defined as the class II binding site. We constructed recombinant invariant chain genes and inspected association of the mutant invariant chains with class II polypeptides. Here we demonstrate that an extracytoplasmic sequence of the invariant chain (aa 81-109) that is only 23 residues away from the transmembrane region is essential for contact with class II polypeptides, whereas the remaining C-terminal part is dispensable for binding. The sequence of invariant-chain-derived peptides that were eluted from class II molecules is contained in this segment and may define the class II binding site of the invariant chain. The membrane-proximal position of this region suggests that the invariant chain and invariant-chain-derived peptides isolated from class II molecules bind to a domain distinct from the class II pocket.

Amino Acid Sequence↗
PubMed1993

Levels of salivary IgA antibodies reactive with bacteria from dental plaque are associated with susceptibility to experimental gingivitis.

Serum IgG, IgA and IgM and salivary IgA antibody levels reactive with extracts from Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eubacterium saburreum and Streptococcus mutans, were measured by enzyme-linked immunosorbent assay in samples from 12 persons before, during and after experimental gingivitis. The participants refrained from cleaning their teeth until 50% of their gingival units showed bleeding after gentle probing, but not longer than 15 days. Samples were taken from serum and saliva, before and during the period of experimental gingivitis, and up to 8 weeks after the start of the experiment. A pattern with minor fluctuations in specific serum and salivary antibody activities was consistently found in all patients. This indicates that immunoregulatory mechanisms succeed in maintaining unchanged antibody levels when plaque load increases. A subgroup of participants with low mean numbers of bleeding gingival units after plaque accumulation, showed significantly higher salivary IgA antibody levels reactive with S. mutans, A. actinomycetemcomitans and E. saburreum, as compared with the subgroup reaching high bleeding after probing scores (p < 0.05). When 1 person with outlying values (p < 0.05) for P. gingivalis was excluded from the tests, the former group also showed statistically significant higher salivary antibody levels to this bacterial species. High levels of salivary IgA directed against bacteria in dental plaque might thus protect against the development of gingivitis.

Adult↗
PubMed1992

Sumatriptan and 5-benzyloxytryptamine: contractility of two 5-HT1D receptor ligands in canine saphenous veins.

Sumatriptan and 5-benzyloxytryptamine are ligands with high affinity for 5-HT1D receptors in the caudate nucleus. Both compounds contracted canine saphenous veins, in vitro. Benzyloxytryptamine was less potent as a contractile agonist than sumatriptan which was less potent than serotonin. In high concentrations (greater than 10(-5) M) serotonin-induced contraction resulted, in part, from activation of alpha-adrenoceptors as determined by blockade of contraction with prazosin (10(-6) M) and idazoxan (10(-6) M). Likewise, benzyloxytryptamine but not sumatriptan also activated contractile alpha-receptors in the canine saphenous vein. Furthermore, benzyloxytryptamine antagonized contraction to sumatriptan in an apparently non-competitive fashion. Thus, benzyloxytryptamine, although possessing some alpha-receptor agonist activity, like sumatriptan, can interact with serotonin receptors in canine saphenous veins. Although effects of sumatriptan and benzyloxytryptamine quantitatively differed in canine saphenous veins, both agents showed similar affinity and agonist efficacy at 5-HT1D receptors in brain. These studies may reflect potential differences between the 5-HT1D receptor in brain and the 5-HT1-like receptor in canine saphenous veins.

Animals↗
PubMed1990

Synthesis and biochemical evaluation of tritium-labeled 1-methyl-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-1H-indazole-3-carboxa mide, a useful radioligand for 5HT3 receptors.

The advent of potent, highly selective 5HT3 receptor antagonists has stimulated considerable interest in 5HT3 receptor mediated physiology and pharmacology. To permit detailed biochemical studies regarding interaction of the indazole class of serotonin (5HT) antagonists with 5HT3 receptors in multiple tissues, we synthesized 1-methyl-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-1H-indazole- 3-carboxamide (LY278584, compound 9) in high specific activity, tritium-labeled form. This radioligand was selected as a synthetic target because of its potency as a 5HT3-receptor antagonist, its selectivity for this receptor viz a viz other 5HT-receptor subtypes, and the ability to readily incorporate three tritia via the indazole N-CH3 substituent. Alkylation of N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-1H-indazole-3-carboxamide (8) with sodium hydride and tritium-labeled iodomethane, followed by HPLC purification, resulted in [3H]-9 with a radiochemical purity of 99% and a specific activity of 80.5 Ci/mmol. This radioligand bound with high affinity to a single class of saturable recognition sites in membranes isolated from cerebral cortex of rat brain. The Kd was 0.69 nM and the Bmax was 16.9 fmol/mg of protein. The specific binding was excellent, and accounted for 83-93% of total binding at concentrations of 2 nM or less. The potencies of known 5HT3-receptor antagonists as inhibitors of [3H]-9 binding correlated well with their pharmacological receptor affinities as antagonists of 5HT-induced decreases in heart rate and contraction of guinea pig ileum, suggesting the central recognition site for this radioligand may be extremely similar to or identical with peripheral 5HT3 receptors.

Animals↗
PubMed1989

Effect of LY53857, a selective 5HT2 receptor antagonist, on 5HT-induced increases in cutaneous vascular permeability in rats.

Both serotonin and histamine increased cutaneous vascular permeability in rats; however, serotonin was approximately 100-fold more potent than histamine. LY53857 (0.1 and 1.0 mg/kg, i.p.), a selective 5HT2 receptor antagonist, blocked serotonin- but not histamine-induced increases in cutaneous vascular permeability. the alpha 1 receptor antagonist, prazosin, did not significantly affect increases in vascular permeability produced by serotonin. These data extend previous studies with LY53857 by further documenting its selectivity as a 5HT2 receptor antagonist. In addition, these results with a selective 5HT2 receptor antagonist provide evidence that 5HT2 receptor activation may be the predominant mechanism associated with vascular permeability changes induced by serotonin.

Animals↗
PubMed1989

MHC class II invariant chains in antigen processing and presentation.

Most protein antigens cannot elicit a T-cell response unless they are processed to peptides, which are then presented to T lymphocytes by surface MHC class II molecules. Recent evidence supports an essential role of the invariant chain associated with class II MHC polypeptides in antigen processing.

Antigens↗
PubMed1989

Serum levels of antibodies against Actinobacillus actinomycetemcomitans in various forms of human periodontitis.

Serum levels of IgG, IgA, and IgM antibodies against extracts from Bacteroides gingivalis PER8, Actinobacillus actinomycetemcomitans Y4, and Bacteroides fragilis NCTC 9343 were determined in three categories of periodontitis patients by means of enzyme-linked immunosorbent assay. The test groups comprised 10 patients with juvenile periodontitis (JP), 18 young patients with severe periodontitis (YP), and 31 patients with adult periodontitis (AP). Nine subjects with healthy periodontium (HP) served as a reference group. Increased frequencies of patients with significantly elevated IgG and IgA antibody values against B. gingivalis and A. actinomycetemcomitans were found in the three periodontitis groups as compared with the HP group. The AP group, however, showed lower IgM values than the other groups. The results support the contention that A. actinomycetemcomitans may play a contributory role in adult periodontitis and that B. gingivalis is a suspected periopathogenic bacterium in juvenile periodontitis. The clinical YP classification was not supported by the present serologic findings.

Actinobacillus↗
PubMed1988

Production and characterization of monoclonal antibodies recognizing head activator in precursor form and immunocytochemical localization of head activator precursor and head activator peptide in the neural cell line NH15-CA2 and in hydra.

A synthetic gene for the hydra neuropeptide head activator (HA) was used to produce large amounts of an HA bacterial fusion protein. From this protein an HA-containing fragment was cleaved out, attached in high copy number to carrier proteins, and used as an immunogen to produce monoclonal antibodies able to recognize head activator in precursor form. Using such antibodies and others with different specificities for HA epitopes in combination with different fixation procedures, we detected HA immunoreactivity in three locations in the HA-rich neural cell line NH15-CA2. A precursor-like HA immunoreactivity was present in the cytoplasm of cells and detected, independent of fixation procedure, by monoclonal antibodies characterized as HA-precursor-specific. With antibodies specific for the HA peptide, two immunoreactivities could be distinguished, one within cells and one at the outer cell membrane. HA was detected within differentiated cells with long processes when crosslinkers such as carbodiimide or glutaraldehyde were applied together with agents like methanol. HA peptide bound to target cells was restricted to small round cells with an undifferentiated morphology, especially to those in the process of cell division. In hydra HA precursor immunoreactivity was localized in interstitial cells and in developing nerve cells. HA peptide immunoreactivity was present in nerve cells, but was more concentrated on and in target cells such as interstitial cells and epithelial cells. In tissue sections immunoreactive cells were especially abundant in regions of high HA content such as hypostome, subhypostomal region, and the future head region of developing buds.

Animals↗
PubMed1987

Antibodies against lipopolysaccharide from Bacteroides gingivalis before and after periodontal treatment.

Specific serum antibody activities of the IgG, IgA and IgM isotypes against lipopolysaccharide (LPS) prepared from Bacteroides gingivalis were measured by an enzyme-linked immunosorbent assay (ELISA) in a group of 12 periodontally healthy subjects and a group of 26 patients with periodontitis. The latter group received periodontal therapy, completed within about 1 yr. A serum sample was obtained from each participant at the first periodontal examination; a second sample was taken about 2 yr later. The mean antibody levels calculated for the healthy group did not change significantly between the first and second examination. The correlation coefficients computed between the two sets of measurements were 0.93, 0.90 and 0.96 for IgG, IgM and IgA respectively (P less than 0.05). Periodontal treatment significantly improved the clinical status of the patients and was followed by a statistically significant mean reduction in specific antibody levels to the LPS preparation (IgG: 15%, IgA: 30% and IgM: 15%).

Adult↗
PubMed1987

IgG subclass distribution of serum antibodies against lipopolysaccharide from Bacteroides gingivalis in periodontal health and disease.

Serum IgG1, IgG2, IgG3 and IgG4 antibody levels directed against lipopolysaccharide (LPS) from Bacteroides gingivalis were measured in the sera from systemically healthy subjects with and without periodontitis. An enzyme-linked immunosorbent assay was used that included coating of microtiter plates with LPS, and subsequent incubation with patient sera followed by mouse monoclonal subclass-specific antibodies, biotinylated sheep anti-mouse IgG and alkaline phosphatase conjugated to streptavidin. Anti-LPS IgG antibodies were dominated by IgG2, and moderate amounts only of IgG1, IgG3 and IgG4 were found. The periodontitis patients had significantly higher anti-LPS IgG1, IgG2 and IgG3 levels when compared to the subjects with healthy periodontium (p less than 0.05, Mann-Whitney test).

Antibodies, Bacterial↗
PubMed1986

Effect of nitrendipine, diltiazem, trifluoperazine and pimozide on serotonin2 (5-HT2) receptor activation in the rat uterus and jugular vein.

The present study explored the calcium source used in serotonin (5-HT)-induced contractions mediated by 5-HT2 receptor activation in the rat uterus and jugular vein in vitro. In the rat uterus, the calcium channel antagonists, nitrendipine and diltiazem, and the neuroleptic agents, trifluoperazine (TFP) and pimozide, antagonized potently and noncompetitively 5-HT-induced contractions. These data are compatible with the contention that 5-HT-induced contractions in uterine smooth muscle require extracellular sources of calcium. In contrast, neither diltiazem nor nitrendipine inhibited the contractile response to 5-HT in the rat jugular vein although 5-HT-induced contractions in the jugular vein required the presence of extracellular calcium. This difference in sensitivity to calcium channel antagonists between the uterus and jugular vein was not related to differences in the receptor occupancy-response curves for 5-HT as these were similar in the rat uterus and jugular vein. Furthermore, in the jugular vein, neither diltiazem nor nitrendipine were markedly effective in blocking contractions produced by potassium chloride, an agent that activates voltage-dependent calcium channels, suggesting that this tissue lacks calcium channels susceptible to blockade by conventional calcium channel antagonists. Although responses to 5-HT in the jugular vein were only affected marginally by calcium channel antagonists, TFP and pimozide produced concentration-dependent rightward parallel shifts of 5-HT-induced contractions in the jugular vein. Furthermore, both TFP and pimozide showed high affinity at 5-HT2 binding sites in rat brain cortical membranes and the apparent dissociation constant at 5-HT2 receptors in the jugular vein was 38 and 31 nM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗