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C L Mills

Publications and source records attributed to C L Mills.

16 recordsLinked to original sources
PubMed1998

Isoproterenol evokes extracellular Ca2+ spikes due to secretory events in salivary gland cells.

Secretory cells should in principle export substantial amounts of calcium via exocytosis since Ca2+ is sequestered in secretory granules. Based on a new technique for measurements of the extracellular calcium concentration in the vicinity of the cell membrane and on the droplet technique, we have monitored the rate of calcium extrusion from salivary gland acinar cells. Isoproterenol (ISP), a beta-adrenergic agonist and powerful secretogogue, evoked no change in the cytosolic free Ca2+ concentration ([Ca2+]i) but induced vigorous extracellular Ca2+ concentration ([Ca2+]i) spiking. The absence of [Ca2+]i elevation and the pulsatile nature of the changes in [Ca2+]i indicate that these spikes are most likely due to calcium release from secretory granules. The cholinergic agonist acetylcholine (ACh), which induces moderate secretion, evoked a marked rise in [Ca2+]i and a smooth rise in [Ca2+]i, most likely induced by plasma membrane calcium pumps, on which shortlasting [Ca2+]i spikes were superimposed. The rate of ISP-induced calcium efflux was very substantial. The calculated calcium loss during the first 100 s of supramaximal stimulation corresponded to a reduction of the total cellular calcium concentration of approximately 0.4 mM. We conclude that in salivary glands, calcium release via exocytosis is one of the main mechanisms extruding calcium from cells to the extracellular milieu.

Acetylcholine↗
PubMed1995

Decreased beta-adrenergic stimulation of glycoprotein secretion in CF mice submandibular glands: reversal by the methylxanthine, IBMX.

beta-adrenergic stimulation of glycoprotein secretion was shown to be decreased in submandibular glands of Cystic Fibrosis (CF) mice. The defective response was partially restored by the methylxanthine, IBMX or cpt-cyclic AMP. Cholinergic stimulation of pancreatic amylase secretion was not affected in CF mice, demonstrating that this is not a generalised depression of protein secretion. The data are the first to show that the CF mouse mimics the protein secretion defect in CF human submandibular cells and that the mechanism of correction of the CF defect is via elevation of cyclic AMP. The results are therefore invaluable towards devising a rational pharmaceutical therapy for CF patients.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Effect of pentoxifylline and progesterone on human sperm capacitation and acrosomal exocytosis.

The effects of pentoxifylline and progesterone on human sperm capacitation and acrosomal exocytosis were investigated using chlortetracycline (CTC) fluorescence. Continuous exposure to 3.60 mM pentoxifylline caused significant changes in distribution of the three CTC patterns (F, B and AR) compared with control suspensions. Initially, the main effect was promotion of the F to B transition, followed by increases in acrosome-reacted (AR) pattern cells as well. Such responses would be consistent with a pentoxifylline-mediated inhibition of cAMP phosphodiesterase leading to increased availability of cAMP. When continuous and short-term exposure to pentoxifylline were compared, very similar responses were observed: both pentoxifylline-treated groups had significantly more capacitated cells (B and AR patterns) than controls. Progesterone tested at 1, 10 and 100 micrograms ml-1 elicited a similar response to that observed with pentoxifylline, with both capacitation and acrosomal exocytosis being stimulated. Cells incubated in 2 x Ca2+ (3.6 mM) medium were even more responsive to progesterone treatment than those in standard 1 x Ca2+ (1.8 mM) medium, with a threefold decrease in cells exhibiting the F pattern (characteristic of uncapacitated, acrosome-intact cells) and a marked increase in AR cells. These responses are consistent with a progesterone-mediated rise in intracellular Ca2+ that could promote completion of capacitation and initiation of acrosomal exocytosis. Used in combination, pentoxifylline followed by progesterone treatment produced significantly more AR pattern cells than either compound individually.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrosome↗
PubMed1994

A possible role for Ca(2+)-ATPase in human sperm capacitation.

Mammalian spermatozoa require extracellular Ca2+, some of which must be internalized, to undergo capacitation and acrosomal exocytosis. The mechanisms controlling the intracellular Ca2+ concentration are unclear, but current evidence suggests that a Ca(2+)-ATPase may be involved. Using treatments that potentially modulate enzyme activity, we investigated this possibility in human spermatozoa; the capacitation state and acrosomal integrity were monitored by chlortetracycline fluorescence. Incubation of cells in the presence of quercetin, a Ca(2+)-ATPase inhibitor, significantly accelerated the transition from the uncapacitated F pattern of chlortetracycline fluorescence to the capacitated, acrosome-intact B pattern within 1 h. This was followed by an increase in the number of cells displaying the capacitated, acrosome-reacted AR pattern. Since most Ca(2+)-ATPases in somatic cells are sensitive to calmodulin, we also investigated the effect of the calmodulin antagonist W-7 on chlortetracycline patterns. At 1-125 mumol l-1, W-7 significantly stimulated capacitation and acrosomal exocytosis. Furthermore, W-7 at 1 mumol l-1 proved to be more effective than W-5, a less potent antagonist, suggesting that the observed responses in human spermatozoa did reflect a calmodulin-sensitive mechanism. When the glucose concentration in the culture medium was varied (from 0 to 5.56 mmol l-1) to alter the availability of ATP for enzyme activity, it was found that a reduced concentration of glucose promoted capacitation more rapidly than did the standard concentration of 5.56 mmol glucose l-1. However, maximal changes, particularly in promoting the shift from the B to the AR pattern of chlortetracycline fluorescence, required millimolar concentrations of glucose during the last few minutes before assessment. Finally, the addition of partially purified mouse sperm decapacitation factor (proposed to activate a Ca(2+)-ATPase and thus maintain a low intracellular Ca2+ concentration) to capacitated human sperm suspensions caused a significant reversal in the capacitation state of cells (from the B to the F pattern). The F pattern of chlortetracycline fluorescence predominates in conditions favouring low concentrations of intracellular Ca2+. From these results, we suggest that a Ca(2+)-ATPase may play an important role during human sperm capacitation. A time-dependent decrease in endogenous enzyme activity would allow the intracellular concentration of Ca2+ to rise to a critical value necessary for initiation acrosomal exocytosis and subsequent successful fertilization.

Acrosome↗
PubMed1993

Ca(2+)-related changes in the capacitation state of human spermatozoa assessed by a chlortetracycline fluorescence assay.

Chlortetracycline (CTC) fluorescence patterns were used to assess Ca(2+)-related changes in the capacitation state of human spermatozoa incubated under conditions that would affect their intracellular Ca2+ levels. Initial experiments were designed to identify consistently occurring patterns and to correlate these with acrosomal status. Incubation for up to 1 h with the ionophore A23187 (10 mumol l-1), known to promote capacitation and acrosomal exocytosis, allowed the identification of three different CTC staining patterns which were very similar to those described for mouse spermatozoa. For this reason, they were given the same nomenclature: 'F'-characteristic of uncapacitated, acrosome-intact cells; 'B'-characteristic of capacitated, acrosome-intact cells; and 'AR'-characteristic of capacitated, acrosome-reacted cells. The distribution of the three patterns in the ionophore-treated suspensions was very different from that in control suspensions treated with dimethylsulfoxide only, with a significantly higher proportion of cells displaying the B and AR patterns and a significantly lower number of cells displaying the F pattern in the ionophore-treated group at all times. A strong concordance was found between the acrosomal status of cells determined using both CTC and fluorescein-conjugated Pisum sativum agglutinin (PSA) staining methods on the same cells. Verification of PSA staining patterns with acrosomal status was obtained by means of transmission electron microscopy. The proportion of cells with uniform fluorescence in the acrosomal region correlated with acrosome-intact cells; those with only equatorial segment staining correlated with fully-reacted cells, and those exhibiting equatorial fluorescence and patchy fluorescence over the rest of the acrosomal region correlated with cells in intermediate stages of exocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcimycin↗
PubMed1992

An antibody against a CFTR-derived synthetic peptide, incorporated into living submandibular cells, inhibits beta-adrenergic stimulation of mucin secretion.

An antibody raised against a peptide in the first nucleotide-binding domain (NBD) of CFTR [1], incorporated into intact rat submandibular acini by hypotonic swelling, inhibited beta-adrenergic stimulated mucin secretion, without affecting cyclic AMP rise. The data are the first to show that a CFTR-antibody-containing cell results in defective stimulation of mucin secretion, as is seen in CF cells, and that this can be reversed by an excessive increase in cyclic AMP.

1-Methyl-3-isobutylxanthine↗
PubMed1992

The cumulative embryo score: a predictive embryo scoring technique to select the optimal number of embryos to transfer in an in-vitro fertilization and embryo transfer programme.

In order to achieve a clinical pregnancy rate higher than that achieved following initial adoption of in-vitro fertilization embryo transfers, more than one embryo is transferred. This has led to a substantial increase in unwanted multiple pregnancy rates with IVF as compared with natural conception. What is therefore required is a simple, clinically useful embryo scoring system, to reflect embryo developmental potential, which will enable the selection of the optimal number of embryos to transfer in order to achieve the maximum pregnancy rate with a low incidence of high order multiple pregnancies. We believe that the Cumulative Embryo Score (CES) achieves these aims. On the day of embryo transfer the grade of each embryo transferred was multiplied by the number of blastomeres to produce a score for each embryo, and summation of the scores obtained for all the embryos transferred gave the CES. The grouped pregnancy rates obtained rose as the CES increased to maximum of 42. A continued increase in the CES above 42 did not result in any further rise in the pregnancy rate. However, an analysis of all our IVF pregnancies showed that the multiple pregnancy rate continued to rise above a CES of 42. By restricting the CES per embryo transfer to 42, 78% of triplet pregnancies and 100% of the quadruplet IVF pregnancies could have been predicted and potentially avoided.

Adult↗
PubMed1991

Introduction of BAPTA into intact rat submandibular acini inhibits mucin secretion in response to cholinergic and beta-adrenergic agonists.

Incorporation of the calcium chelator BAPTA into isolated, intact rat submandibular acini by hypotonic swelling, resulted in complete inhibition of carbamylcholine, noradrenaline and isoproterenol stimulation of mucin secretion. No effects of intracellular BAPTA on cell viability or beta-adrenergic stimulation of cyclic AMP formation were observed. The data are the first to demonstrate that calcium is necessary for beta-adrenergic stimulation of secretion and suggest that Ca2+ provides a common link in the triggering of exocytosis.

Animals↗
PubMed1990

Evidence for the involvement of receptors for fibronectin in the promotion of chick tail segmentation.

In the chick embryo the paraxial mesoderm forms about 50-53 pairs of somites, the precise number depending on the extent to which segmentation proceeds along the tail. However, the terminal mesoderm of the tail fails to segment despite the fact that it appears to contain a reservoir of potential somites. Why does this mesoderm not segment? Some clues can be obtained by comparing this non-segmenting region with the segmental plate in the trunk. We and others have shown that in the trunk region of the chick, cell adhesion plays a major role in somitogenesis and that this increased cell adhesion is associated with compaction of segments of mesoderm immediately prior to segmentation. This compaction can be brought about prematurely by fibronectin and by the specific adhesion peptide GRGDS. The terminal mesoderm in the tail resembles the segmental plate mesoderm in the trunk in undergoing compaction in response to fibronectin and GRGDS. The tail mesoderm differs from the segmental plate mesoderm in that it can also respond to peptides closely related to GRGDS. The response suggests that, whereas the integrin receptors for fibronectin and GRGDS appear to be specific in the presomitic trunk mesoderm, responding only to the specific adhesion-peptide GRGDS, the tail mesoderm may contain more heterogeneous sets of receptors within the integrin/VLA family that respond to a wider variety of ligands. Coincident with these differences is the phenomenon of regional cell death in the tail bud mesoderm. All of these factors are thought to play a role in the extent of segmentation in the paraxial mesoderm of the embryonic chick.

Animals↗
PubMed1989

Mitosis and cell death in the tail of the chick embryo.

Although somites develop from the mesoderm in the tail of the chick embryo, they do not form to the tip of the tail. Previous work has shown that this terminal mesoderm possesses many of the characteristics of the segmental plate mesoderm which gives rise to the somites in the trunk. This investigation is aimed therefore at understanding why the terminal mesoderm fails to form somites. Mitotic and pyknotic rates have been obtained for the tail region of chick embryos between stages 13 and 27. Embryos were treated with colchicine, so that the mitoses were blocked in metaphase, and counts were made on serial sections. The overall mitotic rates were highest between stages 15 and 18. Regions of high mitotic rate, which are an indication of cell synchrony, were found in the tail bud mesoderm though not in a consistent location, and only infrequently near the anterior end of the tail segmental plate. In the trunk however (Stern and Bellairs 1984) a single peak of cell synchrony was routinely found near the cranial end of the segmental plate. It is concluded that the cells of the tail mesoderm are less synchronised in preparation for somitogenesis than are the corresponding mesoderm cells in the trunk. A further conclusion is that the tail bud is not per se a region of high proliferation, though there are patches of high mitotic rate. The overall pyknotic rate reached a maximum at stage 25; peaks of pyknosis corresponded initially with the mitotic peaks and were associated with the ventral ectodermal ridge and the tail gut. By stage 25 however, the high levels of cell death were restricted mainly to the tip of the tail.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Mycobacterium kansasii osteomyelitis of the scaphoid.

A 31-year-old man was found to have a diffuse infection of the wrist and osteomyelitis of the scaphoid caused by Mycobacterium kansasii. The 3-year delay in establishing the diagnosis is characteristic of hand infections caused by atypical mycobacteria. We treated the patient surgically and with antituberculous chemotherapy. This is the only case of M. kansasii osteomyelitis of the scaphoid recorded in the medical literature.

Abscess↗