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Biomedical subjects

J F Roser

Publications and source records attributed to J F Roser.

At least 37 records · Page 2Linked to original sources
PubMed1991

Prolonged pulsatile administration of gonadotrophin-releasing hormone (GnRH) to fertile stallions.

Hormonal effects of prolonged administration of gonadotrophin-releasing hormone (GnRH) were investigated in 7 fertile stallions in winter and summer. The stallions were divided into 4 groups so that 1 animal received 0.625 micrograms of GnRH and each of 2 animals received 1.25, 2.5 or 5.0 micrograms of GnRH subcutaneously every 30 min for 5 days. Daily blood samples were collected from 5 days before to 5 days after treatment for measurement of plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T) and oestrogen conjugates (EC). Five-minute blood samples were collected over a 4 h period prior to, and on the last day of, GnRH treatment in each season for analysis of pulsatile changes in plasma LH concentrations. Mean concentrations of LH and T prior to treatment were higher (P less than 0.05) in summer than winter, whereas plasma FSH and EC concentrations did not differ between seasons. Increasing the dose of GnRH appeared to increase plasma concentrations of LH, FSH and T above baseline in winter (P less than 0.05), whereas a significant effect was not observed in summer. Plasma EC concentrations were not affected by treatment in either season. In GnRH-treated stallions, plasma LH and T concentrations were positively correlated such that the profiles of these hormone concentrations appeared to change in a similar direction over time in winter (P less than 0.01) but not in summer. Plasma concentrations of FSH and EC were not correlated in either season. A positive correlation between plasma LH and FSH concentrations was detected in both winter (P less than 0.01) and summer (P less than 0.02). In contrast, changes in plasma LH and T and plasma FSH and EC concentrations were not correlated over time in either season in control stallions. A positive correlation between plasma LH and FSH concentrations in control stallions was observed in summer (P less than 0.03) but not in winter. Prior to treatment, pulse patterns of LH were similar in both seasons. Following administration of GnRH, irrespective of dose, pulse frequency increased (P less than 0.05) and pulse duration decreased (P less than 0.05) resulting in a decrease in the total amount of LH released per pulse (P less than 0.05) in winter only. Amplitude and interval were not affected by GnRH treatment in either season. The results of this study suggest that the pituitary gland and testes of fertile stallions are more responsive to administration of prolonged pulsatile GnRH in winter than in summer.

Animals↗
PubMed1991

Direct effects of free and conjugated steroids on GnRH stimulated LH release in cultured equine anterior pituitary cells.

Enzymatically dispersed anterior pituitary cells from donor mares were cultured for 48 h in alpha-modified Eagles' medium containing 10% steroid-free horse serum. The cells were then incubated for 24 h in fresh medium oestrogen followed by a 4-h incubation with or without GnRH. Media and cell extracts were analyzed for LH by radioimmunoassay. In the first series of experiments, pituitary cells from Day-3 dioestrous mares were preincubated with ethanol (control) or different concentrations of E2 (10(-11) to 10(-7) M) for 24 h prior to a 4-h incubation without (basal) or with 1.0 nM GnRH. E2 increased (P less than 0.001) GnRH-stimulated LH release with a maximal response obtained at 10(-10) M E2 with an ED50 of 3 x 10(-11) M E2. Also E2 enhanced greatly the responsiveness of the pituitary to varying concentrations of GnRH by decreasing the minimum effective dose and ED50 by 93% and 78%, respectively, and by increasing the maximum response to GnRH by 250%. E2 had no effect on basal LH secretion. In a second experiment, the effects of E2, E1 and E1S on basal and GnRH stimulated LH release were evaluated. Although E1 increased GnRH-stimulated LH release, the maximally effective dose of E1 to enhance LH release and the ED50 for E1 were 100 times greater than those found for E2. E1S had no oestrogenic activity even at concentrations as high as 100 nM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Gonadotrophin and steroid concentrations in jugular and testicular venous plasma in stallions before and after GnRH injection.

Six normal stallions of light horse breeds aged 5-17 years were used from fall to winter to investigate the difference between steroid hormone concentrations in testicular and jugular venous blood before and after exogenous GnRH. At 48 h before experimentation, an indwelling cannula was placed surgically in the testicular vein of the stallion. After the stallion recovered from anaesthesia, a catheter was placed percutaneously in the jugular vein. Each stallion was housed in a tie stall to allow simultaneous sampling of jugular or testicular blood. On the first and second sampling days, respectively, 1 ml of physiological saline solution and a 1 ml solution of GnRH (25 micrograms) were administered intravenously. Samples were taken from both sites at intervals from 60 min before treatment to 780 min after treatment. Plasma was analyzed for luteinising hormone (LH) and follicle-stimulating hormone (FSH), 17 beta-hydroxyandrogens (androgens), oestrone and oestrogen conjugates by radioimmunoassay. Pre-treatment (baseline) plasma concentrations of both LH and FSH between jugular and testicular samples were similar. The difference between basal levels of jugular and testicular androgens, oestrone and oestrogen conjugates were 144-fold, 60-fold and 13-fold respectively, although individual variation was observed. A low dose of exogenous GnRH produced a significant LH and FSH response in testicular and jugular plasma (P less than 0.05). There were no significant changes in steroid secretion caused by the increases in LH and FSH (P greater than 0.05), although individual variation in the androgen response was apparent (P less than 0.1). There was a positive correlation between basal testicular venous androgen levels and the magnitude of the FSH response to GnRH (P less than 0.05). Significant correlations between baseline oestrogens and the magnitude of the gonadotrophin response was not observed. Surgery depressed jugular oestrogen conjugate values (P less than 0.001) when compared to pre-surgical samples. Spermatogenesis also was depressed (P less than 0.01) by surgical manipulation, although total viable spermatozoa counts returned to normal limits within 3-5 months post operatively. We developed a model that allows the study of dynamic endocrine events associated with the hypophyseal-gonadal axis of the stallion. Our findings confirm the presence of a testicular-jugular hormone gradient in the unanaesthetized stallion. We have demonstrated that a relatively low dose of GnRH can induce a significant gonadotrophin response and a variable androgen response, but not a significant oestrogen response. Although baseline levels of androgens and not oestrone and oestrogen conjugates appeared to affect pituitary responsiveness, other steroidogenic components may be involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Androgens↗
PubMed1989

Urinary eCG patterns in the mare during pregnancy.

Blood and urine samples collected from 12 mares at frequent intervals from 25 to 210 d of pregnancy were analyzed for equine chorionic gonadotropin (eCG). Blood and urine samples were collected daily through two consecutive ovulatory periods from five cyclic mares for comparative purposes. Separate radioimmunoassays (RIA) were developed to detect eCG in the urine and plasma. A simple and quick commercial dipstick enzyme-linked immunospecific assay (ELISA), developed for eCG in the blood, was also utilized in this study to detect eCG in the urine. In the 12 pregnant mares, eCG concentrations in both the plasma and urine as detected by RIA rose significantly on Day 40, peaked by Day 60 and slowly dropped to low levels by Day 200. The dipstick ELISA appeared more reliable for eCG in the plasma than in the urine of the five pregnant mares tested. However, on peak days (50 to 60), both the plasma and urine tested positive in all five mares. Similar eCG profiles were observed when urine samples from seven of the mares were assayed in the dipstick ELISA and RIA. The highest percentage of mares (86%) were positive for eCG by ELISA between Days 65 and 85. The highest concentration of eCG in the urine as detected by RIA was observed between Days 55 and 90. ECG-like immunoactivity was not detected by the ELISA in the urine of cyclic mares, but the RIA showed variable patterns with increases in immunoactivity that could not be correlated with physiological events. In summary, eCG in urine follows a similar profile as the eCG in plasma of mares during their first trimester of pregnancy.

Journal Article↗
PubMed1989

Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition.

Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and 11.9 ng/ml respectively; P less than 0.1). The average concentration of prolactin over the last 4 days (Days -3 to 0) had increased by 40% when compared to the average concentration on Days -6, -5, and -4. These findings indicate a rising trend which appears to occur concomitantly with changes in concentrations of 2 mammary components tested, sodium and potassium. Prolactin concentrations did not significantly increase in term mares after oxytocin treatment or in spontaneously foaling mares. However, the preterm induced mares had higher prolactin concentrations during the first stage of labor (19.3 +/- 7.2 ng/ml) than prior to treatment with oxytocin (4.7 +/- 2.0 ng/ml; P less than 0.01). Levels of prolactin in all groups significantly declined by 20-min post-placental expulsion. For the first 30 min after birth, prolactin concentrations in foals from oxytocin-induced mares appeared to be 2-fold higher than those from spontaneously foaling mares. Thereafter, prolactin values declined to baseline values by 48 hrs. When comparing cord arterial plasma with cord venous plasma in each group, prolactin concentrations were similar. However, the average prolactin levels in both the cord artery and vein appeared higher (ave: 1.1 ng/ml) in Group II and III than in Group I (less than 0.5 ng/ml). From these results, the authors suggest that 1) prolactin may have a role in regulating mammary secretory products in mares just prior to parturition; 2) oxytocin may increase prolactin secretion in preterm induced mares; 3) oxytocin induction may have a short term effect to increase circulatory prolactin concentrations in neonates in utero regardless whether their dams were treated preterm or term.

Animals↗
PubMed1988

Urinary hormone analysis as a diagnostic tool to evaluate the ovarian function of female gorillas (Gorilla gorilla).

Daily urine samples were collected from 4 adult female gorillas over 7 menstrual cycles. Urinary oestrone conjugate and pregnanediol-3-glucuronide (PDG) were measured by radioimmunoassay; LH was measured by enzyme immunoassay and each hormone was indexed by creatinine. The quantity of urinary LH during the ovulatory surge was positively correlated with the quantity of PDG excreted during the luteal phase (r = 0.87, P = 0.0013). The observations indicate a relationship between the quality of the LH surge and the levels of PDG in the luteal phase and suggest that both the LH surge and subsequent luteal phase function may be predictable from the oestrogen excretion profile during the follicular phase.

Animals↗
PubMed1987

Characterization of a monoclonal antibody which detects luteinizing hormone from diverse mammalian species.

The present study describes the development and characterization of a monoclonal antibody (518B7) generated against bovine LH (bLH). Although 518B7 was extremely specific for LH, very low species specificity was observed. A RIA using this antibody and radioiodinated equine LH (eLH) showed good sensitivity for all mammalian LH preparations tested, with the exception of human LH (15%, relative to the eLH reference standard). Activities of most mammalian LH's ranged between approximately 50-200%. Much less activity was detected with reptilian LH (less than 1.5%). Amphibian and avian LH fractions were essentially inactive. The reactivities of LH alpha and beta subunits from a variety of mammals clearly showed that the antibody reacts with the beta subunit. Sensitive RIAs were also developed utilizing 125I-bovine and 125I-rat LH. Interestingly, all hormone preparations which showed sufficient reactivity for statistical analysis within the dose ranges used in the present study (0.01-1000 ng/tube) produced a displacement curve parallel to the reference standard. We have also validated the use of 518B7 in detecting LH in serum. Parallel dilution curves relative to purified LH reference standards were observed with equine and bovine serum samples and equine pituitary extract. High (average 94%) recoveries were also seen with bovine serum with known amounts of exogenously added bLH. Similar patterns of LH secretion were detected with a RIA based upon 125I-bLH and 518B7 and a previously described polyclonal antibody-based RIA in bovine serum samples during estrus. Thus, a monoclonal antibody for LH has been produced which can be used to develop sensitive and specific RIAs in many different mammalian species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Properties of equine luteinizing hormone alpha subunit alone and in combination with various beta subunits.

Previous studies have shown that equine luteinizing hormone (eLH) inhibits production of cyclic adenosine monophosphate (cAMP) induced by follicle-stimulating hormone (FSH) in preparations of seminiferous tubules from immature rats. It was also shown that the inhibitory effect was a function of the equine LH (eLH) alpha subunit. To explore this phenomenon further, the intrinsic FSH-like activities of eLH alpha alone and in combination with ovine (o) LH beta, ovine FSH beta, and equine FSH beta were evaluated in several assay systems. In a radioreceptor assay employing 125I-o-FSH and testis membranes from day-old calves, eLH was twice as active as oFSH, eLH alpha was 6% as active as oFSH, and other subunits showed a lack of activity (less than 1.5%). Whereas oLH was only 0.1% as active as oFSH, the hybrid eLH alpha-oLH beta was 3.0% as active. The binding activity of eLH alpha-FSH beta hybrids tended to be higher than the oFSH alpha-FSH beta hybrids. In the cAMP production assay, eLH alpha-FSH beta hybrids exhibited dampened dose-response curves when compared to the oFSH alpha-FSH beta hybrids. In a plasminogen activator assay (PAA) employing granulosa cells from intact 21-24-day-old female rats primed with diethylstilbestrol, eLH had activity comparable to that of oFSH, while eLH alpha was inactive. When eLH alpha was recombined with oFSH beta, eFSH beta, or oLH beta, the PAA stimulatory activity was not altered compared to that of the hybrids oLH alpha-oFSH beta, oFSH alpha-eFSH beta, and the recombinant oLH alpha-oLH beta, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Serum estradiol-17beta concentrations during spontaneous silent estrus and after prostaglandin treatment in the mare.

Serum estradiol-17beta concentrations were determined during silent estrus in the mare. Relationships between serum estradiol-17beta concentration, corpus luteum regression, follicular development, ovulation, prostaglandin treatment and behavioral estrus were investigated. The expression of behavioral estrus was found to be related to the patterns of progesterone and estradiol-17beta secretion during the periovulatory period. When compared to normal estrous cycles, silent estrus was accompanied by a significantly lower maximum serum estradiol-17beta concentration (47.8 vs 34.6 pg/ml), a significantly longer interval from maximum estradiol-17beta concentration to ovulation (1.7 vs 4.0 days), and a significantly shorter interval from corpus luteum regression to ovulation (5.3 vs 2.8 days). Silent estrus following prostaglandin treatment was related to a significantly shorter interval from prostaglandin treatment to ovulation (3.6 +/- 0.4 days) than from normal corpus luteum regression to ovulation (5.3 +/- 0.3 days). Silent estrus appeared to be related to changes in follicular estradiol-17beta secretion and to the pattern of its secretion as related to regression of the corpus luteum. There appeared to be not only less estradiol-17beta present, but also less time available after luteal regression for it to interact with the central nervous system to elicit the changes necessary to cause behavioral estrus. There fore, unusual relationships between luteal function and folliculogenesis can result in one type of silent estrus. Significant correlations (P<0.05) were found between follicle size and serum estradiol-17beta concentration whenever behavioral estrus occurred [follicle diameter in mm = 0.96 (serum estradiol-17beta in pg/ml) + 6.08 and 0.73 (serum estradiol-17beta + 13.32 for control and normal estrus following prostaglandin treatment groups, respectively]. During silent estrus, however, no significant correlations between follicle size and serum estradiol-17beta concentration were observed.

Journal Article↗
PubMed1984

Chemical, biological and immunological properties of pituitary gonadotropins from the donkey (Equus asinus): comparison with the horse (Equus caballus).

Donkey gonadotropins (donkey luteinizing hormone, dLH; donkey follicle-stimulating hormone, dFSH) have been isolated in purified form from 191 donkey pituitaries using essentially the same procedures previously employed for the purification of equine gonadotropins. Chemically, dLH and dFSH were observed to be similar to equine LH (eLH) and FSH (eFSH) in fractionation behavior and glycoprotein nature. Two forms of the dFSH molecule were observed, as is the case for eFSH. Donkey LH had significantly less total carbohydrate (13.5%) and sialic acid (1.9%) than eLH (26.7% and 5.8%, respectively). Carbohydrate (17-21%) and sialic acid (2.4%) content of the two dFSH preparations closely resembled that of eFSH. A slightly higher tyrosine content in the donkey gonadotropins was noted in a comparison of amino acid compositions. Immunologically, in a heterologous FSH radioimmunoassay (RIA), dFSH preparations were equal to or twice as active as eFSH preparations. However, in homologous RIAs for equine chorionic gonadotropin (eCG), eFSH and eLH, both the dLH and dFSH preparations were considerably less active than the equine gonadotropins, and their inhibition curves were all nonparallel. Biologically, in the Steelman-Pohley assay both dFSH preparations were equipotent and as potent as eFSH (approximately 40 times NIH-FSH-S12). In the Sertoli cell assay for cAMP (FSH assay) and the Leydig cell assay for testosterone (LH assay), both dFSH and dLH were 2- or 6-fold more active than eFSH and eLH, respectively. In rat and equine testis FSH homologous radioreceptor assays, dFSH preparations were as active and up to 6-fold more active than eFSH. In contrast, dLH was 10-fold less active than eLH in the equine LH homologous radioreceptor assay. Unlike eLH, dLH was found to possess little intrinsic FSH activity or FSH inhibitory activity, and the small amount of FSH activity observed was most likely due to FSH contamination. Therefore, eLH behaves much like eCG (pregnant mare's serum gonadotropin, PMSG) which also possesses both LH and FSH activity. In contrast, dLH behaves more like donkey chorionic gonadotropin (dCG) which possesses only a low degree of FSH activity.

Animals↗
PubMed1984

Development and characterization of a homologous radioimmunoassay for equine prolactin.

A specific and sensitive homologous radioimmunoassay has been developed for equine prolactin, suitable for measuring prolactin concentrations in serum of horses. The sensitivity of the assay ranged from 0.4 to 0.6 ng/ml and the intra- and inter-assay coefficients of variation averaged 6.9 and 15.4%, respectively, for five doses of hormone. Cross-reactivity with other mammalian and nonmammalian prolactins and growth hormones was less than 20 and 0.3%, respectively. Cross-reactivity with equine growth hormone was less than 0.07%. Equine serum and pituitary extracts showed parallel dilution-response curves with equine prolactin. The percentage recovery of exogenous equine prolactin in serum was 89%. Preliminary analysis of several physiological samples (stallions, pregnant, and nonpregnant mares) yielded values from 0.6 to 12.0 ng/ml.

Animals↗
PubMed1984

Effect of tyrosine modification on the biological and immunological properties of equine chorionic gonadotropin.

The tyrosine residues of equine chorionic gonadotropin have been nitrated with tetranitromethane and the resulting effects on the biological and immunological activities of the hormone studied. All of the tyrosine residues in equine chorionic gonadotropin were found to react with tetranitromethane when a 100-fold molar excess of reagent was used or with an 8.6 molar excess in the presence of 5 M guanidine hydrochloride. Complete nitration abolished the biological activities and decreased the immunological activity of the hormone. The nitration of one tyrosine residue resulted in the loss of 70% of the LH activity of equine chorionic gonadotropin; the FSH activity declined in a similar fashion. Maximal nitration resulted in the loss of about 50% of the immunological activity of the native hormone. Nitrated derivatives of equine chorionic gonadotropin were unable to compete with the native hormone in the rat Leydig cell assay for LH. The results indicate that the tyrosine residues of equine chorionic gonadotropin play an important role in the manifestation of both the FSH and LH activity of the hormone.

Animals↗
PubMed1983

Luteal luteinizing hormone receptors during the postovulatory period in the mare.

Changes in serum luteinizing hormone (LH) and progesterone concentrations, number of luteal unoccupied LH receptors, receptor affinity constants, luteal weights and luteal progesterone concentrations were determined during the postovulatory period in the mare. The number of unoccupied LH receptors and receptor affinity was less during the early (Days 1-4) and late [Day 15 through 3rd day after start of corpus luteum (CL) regression] luteal phases than during the mid-luteal (Days 9-14) phase of the postovulatory period (P less than 0.01). The number of LH receptors per CL increased 21-fold (P less than 0.001) from Day 1 to Day 14. Receptor affinity increased 5-fold (P less than 0.001) from Day 1 to Day 13. Receptor number was highly correlated with receptor affinity (P less than 0.01) and both were highly correlated with serum and luteal progesterone (P less than 0.01). During regression of the CL, the number of LH receptors and receptor affinity decreased concomitantly with serum and luteal progesterone. Morphologically, luteal cell development and degeneration correlated with the change in receptor numbers, affinity constants and luteal and serum progesterone concentrations. Receptor number and affinity, luteal weight and serum and luteal progesterone concentrations did not differ between the CL from multiple ovulations. Random variations in the data observed between CL from multiple and single ovulations suggested that CL from the two groups were not different in structure and function. In summary, the above results suggest that major factors in regulation of progesterone secretion and maintenance of the equine CL are changes in the number of LH receptors and the affinity constants throughout the postovulatory period.

Animals↗
PubMed1982

Comparison of the interaction of equine LH and human chorionic gonadotrophin to equine testicular receptors.

Human chorionic gonadotrophin (hCG) can be used to study horse luteinizing hormone (LH) receptors in stallion testicular tissue. hCG was more stable than horse LH during radioiodination when compared by their abilities to bind to testicular receptor sites. During incubation, neither hormone lost binding activity at 4 degrees C. Horse LH lost binding activity during incubation at 25 degrees C and both hormones lost binding activity at 37 degrees C. Both hormones bound to the same receptor sites which are specific for the hormones. The receptor sites were not degraded when incubated at 4 degrees C for up to 16 h. However, a rapid loss of binding ability occurred at 37 degrees C and a continuous but slower loss at 25 degrees C. Scatchard plots were similar for both hormones. Affinity constants (Ka) of 4 . 5-8 x 10(10) M-1 and receptor site numbers of 3 . 9-7 . 3 x 10(-11) M were calculated from the Scatchard plots, which were linear, indicating a single class of receptors. Similar association and dissociation rate constants were obtained for hCG and horse LH. Association rate constants (K1) between 1 and 32 x 10(5) M-1 sec-1 and dissociation rate constants (K-1) between 1 . 1 and 5 . 6 x 10(-6) sec-1 were observed.

Animals↗
PubMed1982

Effect of PGF-2 alpha on LH receptors in the equine corpus luteum.

As quantified by Scatchard analysis, a 27 000 g crude luteal membrane fraction contained a single population of unoccupied LH receptors characterized by high affinity, ka = 0.647 +/- 0.158 X 10(11) M-1 and low binding capacity, Rt = 4.91 +/- 0.78 X 10(-11) M/mg membrane fraction. Acceptable hormonal specificity, reversibility, saturability, high affinity and tissue specificity indicated that the binding protein was a physiological receptor. To ensure that the methods used for Scatchard analysis were valid, hCG was characterized for specific activity and maximum bindability, non-specific binding was monitored, equilibrium binding assay conditions were optimized and the amount of hormone and receptor degradation was evaluated. Serum concentrations of LH and progesterone significantly increased within 1 h after PGF-2 alpha treatment (P less than 0.05). Serum and luteal progesterone concentrations were significantly reduced (P less than 0.05, P less than 0.01, respectively) by 3 h, long before a decline in luteal LH receptors was observed. A significant decline in receptor number (P less than 0.05) was detected by 36 h. This loss of receptors was associated with a decrease in luteal progesterone (P less than 0.05) and a significant increase in luteal cell degeneration, as judged by morphology. The affinity of the receptor for hCG did not differ at any of the times studied. Luteal weights remained unchanged. PGF-2 alpha treatment of the mare resulted in a rapid decline of serum and luteal progesterone before the loss of luteal LH receptors that presumably leads to the irreversible functional and structural demise of the equine CL.

Animals↗
PubMed1978

Two distinct mechanisms for the initiation of mast cell degranulation. II. A specific inhibition of amine release by serum proteins.

Our experiments have provided additional data in support of the concept that different mast cell activators follow distinct biochemical path-ways in the initiation of secretion and degranulation. To do this we have taken advantage of the observation that some serum proteins, and albumins in particular, have the capacity to inhibit selectively the release of amines from rat peritoneal mast cells initiated by some, but not all, stimuli. We show that the relative inhibition of release obtained is independent of the concentration of activator but dependent upon the concentration of albumin, indicating that the inhibitory process does not involve a direct activator--inhibitor interaction. Finally, our data demonstrate that the inhibition does not interfere with the ability of the acitivator to interact with the mast cell. Thus, cells incubated with activator in the presence of inhibitor become increasingly unresponsive, or desensitized, to subsequent challenge with activator in the absence of inhibitor. These combined data therefore provide evidence, that, in addition to a selectivity in the activation/desensitization process initiated by different mast cell stimuli, at least one of the biochemical steps subsequent to the activation step is also not shared by all mast cell stimuli.

Animals↗