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J Thatcher

Publications and source records attributed to J Thatcher.

At least 19 recordsLinked to original sources
PubMed1999

The influence of Lys68 in decepeptide agonists of C5a on C5a receptor binding, activation and selectivity.

The potent, conformationally biased C5a agonist peptide YSFKPMPLaR (C5a65-74, Y65, F67, P69, P71, D-Ala73) was used as a template to gain insight into the nature and importance of lysine at position 68 in the peptide-receptor interaction. A panel of YSFKPMPLaR analogs with systematic substitutions for Lys68 was evaluated for C5a receptor (C5aR) binding affinity and activation in two well-characterized assay systems: human polymorphonuclear leukocytes (PMNs) and human fetal artery. In addition, we determined the activity of these new analogs in transfected rat basophilic leukemia (RBL) cells in which the Glu at position 199 of the C5aR (wtGlu199) was replaced by a Gln (C5aR-Gln199) or a Lys (C5aR-Lys199). Our results indicated that Lys68 in YSFKPMPLaR plays an important role in binding the C5aR expressed on PMNs and RBL cells. Furthermore, the data indicated that Lys68 interacted with Glu199 of the C5aR in PMNs and RBL cells. In human fetal artery, however, Lys68 substitutions had little or no effect on activity, which suggested that the receptor conformation may be different in this tissue. Thus, the interaction between Lys68 of the decapeptide agonist and Glu199 of the C5aR may be cell type-specific and may form the molecular basis for tissue-specific responses to C5a agonists.

Antigens, CD↗
PubMed1987

Retropharyngeal hematoma as a new cause of acute upper airway obstruction in rheumatoid arthritis.

A patient with severe rheumatoid arthritis (RA) receiving chronic anticoagulation therapy developed acute life threatening airway obstruction. The source of obstruction was a retropharyngeal hematoma compressing the upper airway rather than acute laryngeal dysfunction from the patient's RA. Our case illustrates a new cause of acute stridor and airway obstruction in RA. Publications on upper airway obstruction in RA and airway obstruction secondary to retropharyngeal hematoma are discussed.

Airway Obstruction↗
PubMed1985

Regulation of parathyroid hormone release and cytosolic calcium by extracellular calcium in dispersed and cultured bovine and pathological human parathyroid cells.

Alterations in parathyroid glandular sensitivity to calcium may contribute to the hypersecretion of PTH in hyperparathyroidism. Since the cytosolic calcium concentration may mediate the effects of extracellular calcium on PTH release, we have employed the calcium-sensitive intracellular dye QUIN-2 to examine the relationship between extracellular calcium, cytosolic calcium, and PTH secretion in adult, neonatal, and cultured bovine as well as pathological human parathyroid cells. PTH release was measured using C- and N-terminal radioimmunoassays. Neonatal bovine parathyroid cells showed a greater set-point for secretion (the Ca++ concentration causing half of the maximal inhibition of PTH release) than adult cells (1.27 +/- 0.11 vs. 1.06 +/- 0.11 mM extracellular calcium, P less than 0.01), and a slightly higher extracellular calcium was necessary to raise the cytosolic calcium concentration to a given level in neonatal than in adult bovine parathyroid cells. In individual neonatal and adult cell preparations, there was a close correlation between the set-point for secretion and the "set-point" for cytosolic calcium (r = 0.832, P less than 0.001). In cells from five human parathyroid adenomas, which had an increase in set-point for secretion, the extracellular calcium concentration necessary to raise the cytosolic calcium concentration to a given level was slightly greater than in the neonatal cells. In four preparations of human parathyroid cells there was a significant correlation between the set-points for secretion and cytosolic calcium (r = 0.856, P less than 0.01). Because neonatal bovine and pathological human parathyroid glands show cellular hyperplasia, we studied the temporal relationship between cellular proliferation and the regulation of PTH release and cytosolic calcium concentration in cultured bovine parathyroid cells. Cellular proliferation, estimated by 3H-thymidine incorporation, increased significantly in culture from 104 +/- 10.1 counts/well on day 1 (first 24 h in culture) to 588 +/- 188 and 6,156 +/- 649 counts/well on days 2 and 4, respectively. In cultured cells on day 1, highly Ca++ (2-3 mM) inhibited maximal PTH release by 58.8 +/- 3.2%, which decreased significantly (P less than 0.001) to 38.2 +/- 1.9 and 17.1 +/- 3.7% on days 2 and 4, respectively. The cytosolic calcium observed at 3 mM calcium on day 1 was 701 +/- 43 nM, which declined to 466 +/- 60 and 314 +/- 14 nM on days 2 and 4 (P less than 0.05). There was a close correlation between this progressive decrease in maximal inhibition of PTH release and the cytosolic calcium at high extracellular calcium in cultured cells (r = 0.99, P < 0.001). Thus, during active proliferation of cultured cells, there is an alteration in the regulation of cytosolic calcium at a given extracellular calcium concentration, and changes in the regulation of PTH release and cytosolic calcium by extracellular calcium may be related to enhanced cellular proliferation.

Animals↗
PubMed1985

The acute secretory response to alterations in extracellular calcium concentration and dopamine in perifused bovine parathyroid cells.

We used perifusion of dispersed bovine parathyroid cells to examine the rapid kinetics of the secretory response to alterations in extracellular calcium and to dopamine and compared changes in hormone secretion with alterations in the putative intracellular mediators cytosolic calcium and cAMP. The increase in hormone secretion associated with a reduction in extracellular calcium from 2.0 to 0.75 mM occurred at least as rapidly as the change in calcium concentration, suggesting that the lag time for the stimulation of secretion was of the order of seconds or less. In cells loaded with the intracellular calcium-sensitive dye QUIN 2, on the other hand, the initial activation of hormone secretion by low extracellular calcium was delayed by 30-40 sec. In both QUIN 2-loaded and unloaded parathyroid cells, a subsequent increase in extracellular calcium concentration from 0.75 to 2.0 mM produced a rapid inhibition of hormone secretion which could not be separated temporally from the changes in extracellular calcium. In QUIN 2-loaded cells, the reduction in cytosolic calcium concentration associated with a decrease in extracellular calcium from 2.0 to 0.75 mM took place with a half-time of about 15 sec. The increase in cytosolic calcium concentration on raising extracellular calcium from 0.75 to 2.0 mM had a half-time of approximately 20 sec. Dopamine (10(-5) M) also produced a nearly immediate 3- to 4-fold stimulation of PTH release. Although the increase in hormone secretion preceded the release of cAMP from perifused cells, intracellular cAMP increased 3.4-fold within 10 sec of exposure to dopamine in parallel experiments. Preincubation of perifused cells with dopamine reduced the subsequent secretory response to low extracellular calcium. Conversely, dopamine-stimulated secretion was significantly greater in cells preincubated with 2.0 than in those incubated with 0.75 mM calcium. These results indicate that perifused bovine parathyroid cells respond to secretagogues with a time course comparable to that observed in vivo and that the temporal changes in cytosolic calcium concentration and cellular cAMP are consistent with a mediatory role for these factors in low calcium- and dopamine-stimulated secretion, respectively. In addition, at least a portion of the secretory response to low calcium and dopamine may come from a common cellular pool of PTH.

Aminoquinolines↗
PubMed1984

Effect of the phorbol ester TPA on PTH secretion. Evidence for a role for protein kinase C in the control of PTH release.

Parathyroid hormone (PTH) secretion is stimulated by low extracellular calcium (Ca2+) in association with a reduction in cyosolic Ca2+, indicating that this cell type does not conform to classical models of stimulus-secretion coupling. We used the phorbol ester TPA (12-O-tetradecanoyl phorbol 13-acetate), which directly activates protein kinase C, to investigate the possible role of this enzyme in the unusual secretory properties of the parathyroid cell. TPA causes a dose-dependent stimulation of PTH release inhibited by high extracellular Ca2+ (EC50 = 10 nM) but has relatively little effect on secretion stimulated by low Ca2+. This effect was mimicked by the beta 4-isomer of phorbol 12,13-didecanoate which also activates kinase C, but not by the alpha 4-isomer, which has no effect on this enzyme. TPA does not modify cellular cAMP or cytosolic Ca2+ in the parathyroid cell indicating that its effects on PTH secretion are not mediated indirectly via changes in these second messengers. These results suggest that inhibition of PTH release at high Ca2+ might be related to a reduction in protein kinase C activity which can be overcome when the enzyme is directly activated by TPA.

Animals↗
PubMed1984

Relationship between parathyroid hormone secretion and cytosolic calcium concentration in dispersed bovine parathyroid cells.

The parathyroid cell is unusual among exocytotic systems in that low extracellular Ca2+ concentrations stimulate, while high Ca2+ concentrations inhibit, parathyroid hormone (PTH) release, suggesting that this cell might have unique secretory mechanisms. In the present studies, we used the Ca2+-sensitive fluorescent dye QUIN -2 to examine the relationship between cytosolic Ca2+ concentration and PTH release in dispersed bovine parathyroid cells. The secretagogue dopamine, which enhances PTH release 2- to 3-fold in association with 20- to 30-fold increases in cellular cAMP, had no effect on the cytosolic Ca2+ level (261 +/- 28 vs. 236 +/- 22 nM for control cells at 1 mM extracellular Ca2+; P greater than 0.05). Dibutyryl-cAMP, which produces a comparable stimulation of PTH release, likewise did not modify the level of cytosolic Ca2+. Removal of extracellular Ca2+ produced a further decrease of the cytosolic Ca2+ to 82 +/- 10 nM. However, PTH secretion persisted at a near maximal rate despite this decrease of extracellular and cytosolic Ca2+ and was 95 +/- 2.5% of the rate of hormonal release at 0.5 mM extracellular Ca2+. In contrast, addition of the divalent cation ionophore ionomycin to parathyroid cells at 1.0 mM extracellular Ca2+ inhibited PTH secretion in association with an increase in cytosolic Ca2+ from 230 +/- 13 nM to 570 +/- 50 nM. Moreover, the magnitude of the ionomycin-induced reduction in PTH secretion (64 +/- 4% relative to the secretory rate at 0.5 mM Ca2+) was equivalent to the inhibition of PTH release caused by 1.5 mM extracellular Ca2+ (64 +/- 6%), which increased the cytosolic Ca2+ to similar levels (450 +/- 48 nM). Thus, the parathyroid cell differs from secretory cells thought to operate by stimulus-secretion coupling in the following ways: changes in PTH release can occur without detectable alterations in the cytosolic Ca2+ concentration, maximal rates of PTH secretion occur at cytosolic Ca2+ concentrations that fail to support exocytosis in other cell types, and increases in the cytosolic Ca2+ concentration due to ionomycin inhibit rather than stimulate PTH release. Therefore, the control of PTH secretion by Ca2+ and other secretagogues may involve previously undefined mechanisms whereby hormonal release is relatively independent of the cytosolic Ca2+ at low levels of this parameter and is inversely related to cytosolic Ca2+ at higher levels of intracellular Ca2+.

Aminoquinolines↗
PubMed1983

E-rosette inhibition and tumour recurrence in early breast cancer.

The relationship of serum blocking activity and susceptibility to tumour recurrence using E-rosette inhibition by normal allogenic lymphocytes was evaluated before and after operation in 20 patients with early breast cancer. Preoperative serum inhibition levels did not predict recurrent tumour. The mean postoperative inhibition in patient with recurrence was significantly greater than in those without recurrence. Postoperative testing only in a group of 124 patients showed that the development of local tumour recurrence was preceded by significantly greater inhibition of E-rosetting than occurred in patients without recurrence. The application of a threshold level of serum inhibition of 15 per cent distinguishes patients who are unlikely to develop tumour recurrence over a 4-year follow-up period. Serial measurements of serum inhibition at 6-monthly intervals over 2 years did not add to the predictive value of this test.

Breast Neoplasms↗
PubMed1983

Effects of extracellular Ca++ and Mg++ on cytosolic Ca++ and PTH release in dispersed bovine parathyroid cells.

We studied the effects of varying extracellular concentrations of Ca++ and Mg++ on cytosolic Ca++ concentration and PTH release by incorporating the Ca++-sensitive, fluorescent dye "QUIN 2" into dispersed bovine parathyroid cells. Increasing extracellular Ca++ from 0.5 to 2.0 mM led to a dose-dependent increase in cytosolic Ca++ from 179 +/- 8 to 646 +/- 68 nM (mean +/- SE, N = 13; P less than 0.01), which correlated closely (r = -.987, P less than .001) with the suppression of PTH secretion by the same Ca++ concentrations. Raising extracellular Mg++ from 0.5 to 3 mM also caused a dose-related increase in cytosolic Ca++ from 176 +/- 10 to 277 +/- 15 nM (N = 12, P less than 0.01) which correlated (r = -.959, P less than .01) with inhibition of PTH release. These results show a close inverse relationship between cytosolic Ca++ and PTH release with alterations in extracellular Ca++ or Mg++. Cytosolic Ca++ may, therefore, act as a second messenger mediating the effects of these divalent cations on PTH release.

Aminoquinolines↗
PubMed1981

Fixation of tibial components of knee prostheses.

Twelve different tibial components were compared for fixation. The components included compartmental, anteriorly joined, posterior-cruciate retaining, and one-place with one, two, or three fixation posts; all-plastic or with a metal tray. The apparatus applied compressive load with anterior-posterior force, rotational torque, or varus-valgus moment. The relative deflections, both compressive and distractive, were measured between the component and the bone. The least deflections occurred with one-piece metal-tray components with one or two posts and with one-piece plastic components with a post on each side. Compartmental components deflected the most.

Biomechanical Phenomena↗
PubMed1978

Importance of methodology in demonstrating depression of T-lymphocyte levels.

A comparison has been made of 3 methods of determining E rosettes in young, healthy people, women with breast cancer and an age-matched group of healthy women, in an attempt to explain the wide variations in T-cell levels in different disease states reported by different workers. The greatest difference in levels of E-rosetting cells between the different groups was seen in incubation of 1 1/2 h at 4 degrees C. Much of the difference seen in these comparisons disappeared after overnight incubation at 4 degrees C, which was associated with an increased T-cell level in all groups. Consequently, although maximal levels of T lymphocytes as determined by E rosetting are found using overnight incubation, a short incubation period may be superior for demonstrating subtle depressions in levels of T lymphocytes as seen in elderly people and cancer patients. This depression is not considered to be cancer specific, because of the findings in the age-matched control group and similar findings in benign disease states.

Adult↗
PubMed1977

Masking of receptors for sheep erythrocytes on human T-lymphocytes by sera from breast cancer patients.

Sera from 140 breast cancer patients and 38 controls were tested for their ability to inhibit sheep erythrocyte (E) rosette formation by normal, allogeneic lymphocytes. Inhibition of rosette formation by greater than 20% was found with 65% of stage I sera, 91% of stage II sera, 56% of stage III sera, and all stage IV sera. In contrast, only 13% of control sera was inhibitory. The inhibitory factor was found to bind to only a proportion of T-lymphocytes and could be removed from these lymphocytes by mild proteolytic digestion or extended washing. Examination of the properties of the inhibitory factor indicated that it differed from other substances that reportedly inhibited E-rosette formation.

Binding Sites↗
PubMed1976

T and B lymphocytes in breast cancer stage relationship and abrogation of T-lymphocyte depression by enzyme treatment in vitro.

B and T lymphocytes have been measured in 100 women--71 patients with breast cancer and 29 controls--using sheep-erythrocyte rosetting techniques. Compared with controls (healthy women or patients with benign breast disease), there is a highly significant depression of T-cell percentage in all stages of breast cancer except locally advanced (stage 3) disease. These stage-3 cases seem to constitute a biologically distinct group. T-cell percentages in early (stage 1) patients overlap with those seen in stages 3 and 4, raising the possibility that there are in stage 1 two subpopulations of T-cell values that are associated with differences in subsequent tumour progression. B-lymphocyte levels are similar in all groups. Low T-cell levels return to normal after incubation with papain in virto but fall again after resuspending the treated lymphocytes in autologous (cancer) serum. The results suggest that T-cell depression is due to a masking factor on the surface of some T lymphocytes which is also present in the serum of cancer patients, and removable by enzyme digestion.

Adult↗