RESUMO
BACKGROUND: High-quality care for termination of pregnancy (TOP) requires pain to be effectively managed; however, practices differ, and the available guidelines do not specify optimal strategies. OBJECTIVE: To guide providers in effective pain management for second-trimester medical and surgical TOP. SEARCH STRATEGY: We searched PubMed, Cochrane and Embase databases, and the US National Library of Medicine clinical trials registry, from inception to the end of June 2019, and hand-searched reference lists. SELECTION CRITERIA: Trials comparing pain management strategies with no treatment, placebo or active interventions during induced medical or surgical TOP, occurring between 13 and 24 weeks of gestation, and reporting direct or indirect measures of pain. DATA COLLECTION AND ANALYSIS: Both authors summarised and systematically assessed the evidence and risk of bias using standard tools. MAIN RESULTS: We included seven medical and four surgical TOP studies, with 453 and 349 participants, respectively. The heterogeneity of interventions and outcomes prevented pooled analyses. Medical TOP: women receiving routine or continuous epidural analgesia experienced mild pain. The prophylactic use of nonsteroidal anti-inflammatory drugs (NSAIDs) decreased pain (mean difference -0.5, P < 0.001) and additional opioid requirements (3.5 versus 7 mg, P = 0.04) compared with placebo/other treatment. Paracervical block was ineffective. No studies assessed intramuscular (IM)/intravenous (IV) opioid or nonpharmacological treatment. Surgical TOP: general anaesthesia/deep IV sedation alleviated pain. Nitrous oxide was ineffective. No studies assessed moderate IV sedation, IV/IM opioid, paracervical block without sedation, NSAID or nonpharmacological treatment. CONCLUSION: Based on limited data, regional analgesia and NSAIDs mitigated second-trimester medical TOP pain; general anaesthesia/deep IV sedation alleviated surgical TOP pain. TWEETABLE ABSTRACT: Although women experience intense pain during second-trimester termination of pregnancy, few data are available to inform their treatment.
Assuntos
Aborto Induzido/efeitos adversos , Dor Pós-Operatória/prevenção & controle , Dor/prevenção & controle , Aborto Induzido/métodos , Analgesia Epidural , Analgésicos Opioides/uso terapêutico , Anestesia Geral , Anestesia Intravenosa , Anestesia Obstétrica , Anti-Inflamatórios não Esteroides/uso terapêutico , Feminino , Humanos , Gravidez , Segundo Trimestre da GravidezRESUMO
Given the overall safety profile and increasing availability of medical pregnancy termination drugs, we asked: would the mifepristone-misoprostol regimen for medical termination at ≤10 weeks of gestation meet US Food and Drug Administration regulatory criteria for over-the-counter (OTC) approval, and if not, what are the present research gaps? We conducted a literature review of consumer behaviours necessary for a successful OTC application for medical termination at ≤10 weeks of gestation and identified crucial research gaps. If we were to embark on a development programme for OTC or more generally, self-use of medical termination, the critical elements missing are the label comprehension, self-selection and actual use studies. TWEETABLE ABSTRACT: Considering medical pregnancy termination through the over-the-counter regulatory lens clarifies critical evidence gaps.
Assuntos
Abortivos não Esteroides/administração & dosagem , Abortivos Esteroides/administração & dosagem , Aborto Induzido/métodos , Mifepristona/administração & dosagem , Misoprostol/administração & dosagem , Primeiro Trimestre da Gravidez , Aborto Induzido/ética , Aprovação de Drogas , Quimioterapia Combinada , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Medicamentos sem Prescrição , Gravidez , Estados Unidos , United States Food and Drug AdministrationRESUMO
STUDY QUESTION: Is there a pharmacodynamic interaction between ulipristal acetate (UPA) 30 mg for emergency contraception and a daily progestin-only contraceptive pill, desogestrel (DSG) 0.75 mg, when initiated the next day? SUMMARY ANSWER: In this study, DSG impaired the ability of UPA to delay ovulation, but UPA had little impact on the onset of contraceptive effects due to DSG. WHAT IS KNOWN ALREADY: UPA is a progesterone receptor modulator used for emergency contraceptive (EC) at the dose of 30 mg. UPA delays ovulation by at least 5 days when administered in the mid to late follicular phase. In theory, potent progestins could reactivate progesterone signaling that leads to follicle rupture, thereby impacting the effectiveness of UPA as EC. In addition, UPA could alter the onset of the contraceptive effect of progestin-containing contraceptives started immediately after UPA. STUDY DESIGN, SIZE, DURATION: A single-blind (for observer), placebo-controlled, partial crossover study was conducted in two sites [Dominican Republic (DR) and the Netherlands (NDL)] over 11 months from October 2012 to September 2013. Healthy female volunteers participated in two of the three treatment cycles separated by a washout cycle. Treatment combinations studied were as follows: (i) a single 30 mg dose of UPA followed by 75 µg per day DSG for 20 days, (ii) a single 30 mg dose of UPA followed by 20 days of placebo matching that of DSG (PLB2) or (iii) one tablet of placebo-matching UPA (PLB1) followed by 75 µg per day DSG for 20 days. Participants were randomized to one of the three treatment sequences (UPA + DSG/UPA + PLB2, PLB1 + DSG/UPA + DSG and UPA + PLB2/PLB1 + DSG) when a lead follicle was ≥ 14 to <16 mm diameter on transvaginal ultrasound imaging (TVU). PARTICIPANTS/MATERIAL, SETTING, METHODS: A total of 71 women were included, and 49 were randomized to a first treatment combination of the three period sequences (20 in the DR and 29 in the NDL); 41 of the 49 continued and completed two treatment combinations (20 in the DR and 21 in the NDL). MAIN RESULTS AND THE ROLE OF CHANCE: Initiating DSG treatment the day after UPA significantly reduced the ovulation delaying effect of UPA (P = 0.0054). While ovulation occurred in only one of the 29 UPA-only cycles (3%) in the first 5 days, it occurred in 13 of the 29 (45%) UPA + DSG cycles. LIMITATIONS, REASONS FOR CAUTION: This was a small, descriptive, pharmacodynamic study in which some findings differed by study site. Distinguishing between a cystic corpus luteum and a luteinized unruptured follicle (LUF) by TVU was difficult in some cases; however, the investigators reached consensus, when the study was still blinded, regarding ovulation based on hormone levels and careful review of daily TVU images. WIDER IMPLICATIONS OF THE FINDINGS: Initiating the use of a DSG progestin-only pill (POP) immediately after UPA reduces the ability of UPA to delay ovulation and thus may decrease its efficacy as EC. If starting a DSG POP after using UPA for EC, and possibly any progestin-only method, consideration should be given to delaying for at least 5 days after UPA intake in order to preserve the ovulation delaying effects of UPA.
Assuntos
Anticoncepção Pós-Coito/métodos , Anticoncepcionais Orais Sintéticos/administração & dosagem , Desogestrel/administração & dosagem , Norpregnadienos/uso terapêutico , Ovulação/efeitos dos fármacos , Adolescente , Adulto , Anticoncepcionais Orais Sintéticos/uso terapêutico , Estudos Cross-Over , Desogestrel/uso terapêutico , República Dominicana , Feminino , Humanos , Países Baixos , Estudos Prospectivos , Método Simples-Cego , Fatores de Tempo , Resultado do Tratamento , Adulto JovemRESUMO
BACKGROUND: Unsafe termination of pregnancy is a major contributor to maternal morbidity and mortality. Task sharing termination of pregnancy services between physicians and mid-level providers, a heterogeneous group of trained healthcare providers, such as nurses, midwives and physician assistants, has become a key strategy to increase access to safe pregnancy termination care. OBJECTIVES: To systematically review the evidence to assess whether termination of pregnancy services by nonphysician providers can be performed safely and effectively. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, MEDLINE in process and other nonindexed citations and POPLINE. SELECTION CRITERIA: We included randomised controlled trials (RCTs), as well as clinical studies, using study designs that compared efficacy, safety and acceptability of termination of pregnancy services by physicians versus other provider groups. Data collection and analysis Two reviewers independently extracted the data, and we performed a meta-analysis where appropriate using RevMan. Quality assessment of the data used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. MAIN RESULTS: We identified five controlled studies comprising 8908 women undergoing first-trimester surgical termination of pregnancy (one RCT and three prospective cohort studies) and medical termination of pregnancy (one RCT). The mid-level provider group included midwives, nurses, auxiliary nurse midwives and physician assistants trained in termination of pregnancy services. Safety and efficacy outcomes, including incomplete termination of pregnancy, haemorrhage, injury to the uterus or cervix, did not differ significantly between providers. AUTHOR'S CONCLUSIONS: Limited evidence indicates that trained mid-level providers may effectively and safely provide first-trimester surgical and medical termination of pregnancy services. Data are limited by the scarcity of RCTs and biases of the cohort studies.
Assuntos
Aborto Induzido/normas , Atenção à Saúde/normas , Tocologia/normas , Enfermeiros Obstétricos/normas , Assistentes Médicos/normas , Cuidado Pré-Natal/normas , Aborto Induzido/métodos , Feminino , Humanos , Gravidez , Estudos Prospectivos , Melhoria de Qualidade , Ensaios Clínicos Controlados Aleatórios como Assunto , Viés de Seleção , Resultado do TratamentoRESUMO
OBJECTIVE: To compare women's acceptance of misoprostol-only medical termination of pregnancy (TOP) with surgical TOP. DESIGN: Prospective cohort study. SETTING: Termination of pregnancy clinics in New Delhi, Mumbai, Hanoi, Tbilisi, Trivandrum and Yerevan. POPULATION: Women requesting TOP, at 63 days of gestation or less, at study sites where both medical and surgical methods were available. METHODS: Serial surveys eliciting measures of women's satisfaction and acceptance of TOP method were administered. Data were analysed using cross-tabulation and logistic regression to determine if TOP method was predictive of acceptability. MAIN OUTCOME MEASURES: Patient acceptance. RESULTS: High acceptability of both surgical and misoprostol-only TOP. CONCLUSIONS: Where medical TOP with mifepristone is not available, misoprostol-only medical TOP is acceptable to women who have the choice between medical or surgical techniques.
Assuntos
Abortivos não Esteroides , Aborto Induzido/métodos , Misoprostol , Satisfação do Paciente/estatística & dados numéricos , Curetagem a Vácuo , Abortivos não Esteroides/administração & dosagem , Adulto , Esquema de Medicação , Feminino , Seguimentos , Humanos , Modelos Logísticos , Misoprostol/administração & dosagem , Preferência do Paciente/estatística & dados numéricos , Gravidez , Estudos ProspectivosRESUMO
OBJECTIVE: To review published reports of first-trimester medical abortion regimens that do not include mifepristone. METHODS: Reports listed in Pubmed and Medline on prospective and controlled trials of the efficacy of misoprostol, alone or associated with methotrexate, for first-trimester abortion were analyzed if they included more than 100 participants and were published since 1990. RESULTS: The efficacy of regimens using misoprostol alone ranged from 84% to 96%, and when misoprostol was used with methotrexate the efficacy ranged from 70% to 97%. Efficacy rates were influenced by follow-up interval. Treatment for infection, bleeding, and incomplete abortion were infrequent with both methods (0.3%-5%). CONCLUSION: Alone or in combination with methotrexate, misoprostol is an efficacious alternative to mifepristone for the medical termination of pregnancy.
Assuntos
Abortivos Esteroides , Aborto Induzido/métodos , Metotrexato/administração & dosagem , Mifepristona/administração & dosagem , Quimioterapia Combinada , Feminino , Humanos , Gravidez , Primeiro Trimestre da GravidezRESUMO
OBJECTIVE: Ulipristal acetate (UPA) 30 mg is safe and effective for emergency contraception (EC). This prospective open-label exploratory study was conducted to obtain additional data on the pharmacodynamic effects of repeated dose of UPA 30 mg during an 8-week period (effects on ovulation inhibition, hormonal levels, endometrium and cervical mucus). Safety and tolerability data of repeated use of UPA EC were also collected. STUDY DESIGN: A total of 23 healthy female, healthy sterilized women participated in two substudies receiving UPA for 8 consecutive weeks. In substudy 1, UPA 30 mg was administered every 7 days (Q7D n=12); while in substudy 2, every 5 days (Q5D n=11). Subjects were monitored three times a week in a baseline cycle and during treatment with transvaginal ultrasounds, hormonal measurements and cervical mucus evaluation. Laboratory safety measurements and standard surrogate thrombosis risk markers were measured at baseline and within a few days of the last tablet. A luteal phase endometrial biopsy was taken in the baseline cycle and posttreatment. RESULTS: A total of 11/12 (91.7%) and 8/11 (72.7%) of the subjects ovulated at least once in substudy Q7D and Q5D, respectively, with similar, normal hormonal profiles. No effect on cervical mucus was observed. All biopsies were classified as benign in both substudies; 5/11 biopsies on Q5D posttreatment were classified as nonphysiological with some of typical progesterone receptor modulator-associated endometrial changes. UPA was well tolerated in both treatment arms while clinical laboratory results and surrogate thrombosis markers were reassuring. CONCLUSIONS: Repeat use of 30 mg oral UPA every 5 or 7 days for 8 weeks initially delays follicular rupture but ovulation eventually occurs with time in most subjects. Safety data indicate that UPA 30 mg could be safely administered if needed more than once for EC in a given menstrual cycle. IMPLICATIONS: These data demonstrate that repeated use of UPA 30 mg is safe. However, ovulation eventually occurs in a high proportion of women in spite of repeated treatments in both studied regimens. Nevertheless, since the stage of follicular development of women seeking initial or repeat EC use is generally unknown, the repeated use of UPA may still delay follicular rupture and prevent an unintended pregnancy in the event of further unprotected intercourse.
Assuntos
Anticoncepção Pós-Coito/métodos , Anticoncepcionais , Norpregnadienos/farmacologia , Adolescente , Adulto , Biópsia , Muco do Colo Uterino/efeitos dos fármacos , Endométrio/efeitos dos fármacos , Endométrio/patologia , Feminino , Humanos , Fase Luteal , Norpregnadienos/administração & dosagem , Norpregnadienos/efeitos adversos , Folículo Ovariano/efeitos dos fármacos , Folículo Ovariano/fisiologia , Ovulação/efeitos dos fármacos , Gravidez , Estudos ProspectivosRESUMO
A degenerative oligodeoxyribonucleotide probe deduced from the first 19 amino acids of the mature alkaline phosphatase IV (APase IV) protein was used to clone a DNA fragment internal to the coding region of the phoAIV gene of Bacillus subtilis. An insertional mutation was constructed in the phoAIV locus using the integrative plasmid, pJM103, containing the cloned DNA fragment. The strain with the interrupted phoAIV gene showed no detectable APase IV product on Western-blot analysis. The impact of the phoAIV interruption on total APase production in B. subtilis 168 was analyzed under both phosphate starvation and sporulation culturing conditions. The mutation in phoAIV reduced total APase-specific activity by 75% in phosphate-starved cells, and resulted in the elimination of a salt-extractable membrane APase, as well as the secreted APase IV. Analysis of this membrane APase indicated that it is a phoAIV gene product which is localized within the membrane fraction of the lysed cell and not secreted. There was no effect on the production of sporulation APase. The phoAIV::pJM103 insertion was mapped and determined to be located at approx. 73 degrees on the B. subtilis 360 degrees chromosome.
Assuntos
Fosfatase Alcalina/biossíntese , Bacillus subtilis/genética , Sequência de Aminoácidos , Bacillus subtilis/enzimologia , Sequência de Bases , Western Blotting , Mapeamento Cromossômico , Clonagem Molecular , Genes Bacterianos , Dados de Sequência Molecular , MutaçãoRESUMO
The first alkaline phosphatase (APase) structural gene mutant of Bacillus subtilis 168 was constructed by using a clone identified by hybridization to a synthetic degenerative oligonucleotide. The design of the probe was based on the first 29 amino acids of the sequenced mature APase III protein, which had been isolated from the secreted fraction of vegetative, phosphate-starved cells. DNA sequencing of the clone revealed the first 80 amino acids of the APase III protein, including a typical procaryotic signal sequence of 32 amino acids preceding the start of the mature protein. The 29 amino acids encoded by the predicted open reading frame immediately following the signal sequence are identical to the first 29 amino acids of the sequenced mature protein. This region shows 80% identity to strand A of the beta sheet that is very well conserved in Escherichia coli and mammalian APases. A phoAIII structural mutant was constructed by insertional mutagenesis with a fragment internal to the coding region. The effects of this mutation on APase production in B. subtilis 168 were analyzed under both phosphate starvation and sporulation conditions. The mutation in APase III reduced the total vegetative APase specific activity by approximately 40% and sporulation APase specific activity by approximately 45%. An APase protein was isolated from sporulating cells at stage III and was identified as APase III by protein sequencing of the amino terminus and by its absence in the phoAIII mutant. The APase III gene has been mapped to approximately 50 degrees on the B. subtilis chromosome.
Assuntos
Fosfatase Alcalina/genética , Bacillus subtilis/genética , Genes Bacterianos , Isoenzimas/genética , Mutação , Fosfatase Alcalina/biossíntese , Sequência de Aminoácidos , Bacillus subtilis/enzimologia , Bacillus subtilis/crescimento & desenvolvimento , Clonagem Molecular/métodos , DNA Recombinante/metabolismo , Escherichia coli/genética , Isoenzimas/biossíntese , Cinética , Dados de Sequência Molecular , Plasmídeos , Homologia de Sequência do Ácido Nucleico , Esporos Bacterianos/enzimologia , Esporos Bacterianos/fisiologiaRESUMO
Bacillus subtilis has an alkaline phosphatase (APase) gene family composed of at least four genes. All members of this gene family are expressed postexponentially, either in response to phosphate starvation or sporulation induction or, in some cases, in response to both. The phoA gene (formerly called phoAIV) and the phoB gene (formerly called phoAIII) products have both been isolated from phosphate-starved cells, and a mutation in either gene decreased the total APase expressed under phosphate starvation conditions. Data presented here show that a phoA phoB double mutant reduced APase production during phosphate starvation by 98%, indicating that these two genes are responsible for most of the APase activity during phosphate-limited growth. The promoter for phoA was cloned and used, with the phoB promoter, to examine phosphate regulation in B. subtilis. phoA-lacZ reporter gene assays showed that the expression of the phoA gene commences as the culture enters stationary phase as a result of limiting phosphate concentrations in the growth medium, thereby mimicking the pattern of total APase expression. Induction persists for approximately 2 h and is then turned off. phoA is transcribed from a single promoter which initiates transcription 19 bp before the translation initiation codon. PhoP and PhoR are members of the two-component signal transduction system believed to regulate gene expression in response to limiting phosphate. The expression of phoA or phoB in response to phosphate starvation was equally dependent on PhoP and PhoR for induction. lacZ-promoter fusions showed that both phoA and phoB were hyperinduced, or failed to turn off induction after 2 h, in a spo0A strain of B. subtilis. Mutations in genes which are required for phosphorylation of Spo0A, spo0B and spo0F, also resulted in phoA and phoB hyperinduction, suggesting that phosphorylation of Spo0A is required for the repression of both APases in wild-type strains. The hyperinduction of either APase gene in a spo0A strain was dependent on PhoP and PhoR. Analysis of a phoP-lacZ promoter fusion showed that the phoPR operon is hyperinduced in a spo0A mutant strain, suggesting that Spo0A approximately P represses APases by repressing phoPR transcription. We propose a model for PHO regulation in B. subtilis whereby the phoPR operon is transcribed in response to limiting phosphate concentration, resulting in activation of the PHO regulon transcription, including transcription of phoA and phoB. When the phosphate response fails to overcome the nutrient deficiency, signals for phosphorylation of Spo0A result in production of Spo0A approximately P, which represses transcription of phoPR, thereby repressing synthesis of the PHO regulon.
Assuntos
Fosfatase Alcalina/biossíntese , Fosfatase Alcalina/genética , Bacillus subtilis/enzimologia , Bacillus subtilis/genética , Óperon , Regiões Promotoras Genéticas , Regulon , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Primers do DNA , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Escherichia coli , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Genótipo , Isoenzimas/biossíntese , Isoenzimas/genética , Cinética , Modelos Genéticos , Dados de Sequência Molecular , Fosfatos/metabolismo , Plasmídeos , Mapeamento por Restrição , Transcrição GênicaRESUMO
Bacillus subtilis has an alkaline phosphatase multigene family. Two members of this gene family, phoAIII and phoAIV, were cloned, taking advantage of in vitro constructed strains containing a plasmid insertion within one or the other of the structural genes. The DNA sequences of the two genes showed approximately 64% identity at the DNA level and 63% identity in the deduced primary amino acid sequences. The phoAIII and phoAIV genes code for predicted proteins of 47,149 and 45,935 Da, respectively. Comparison of the deduced primary amino acid sequence of the mature proteins with other sequenced alkaline phosphatases from Escherichia coli, yeast, and humans shows 25-30% identity. Based on the refined crystal structure of E. coli alkaline phosphatase, it appears that the active site and the core of the structure are retained in both Bacillus alkaline phosphatases. However, both proteins are truncated at the amino terminus compared with other mature alkaline phosphatases, three sizable surface loops of E. coli are deleted, and a minidomain is replaced with a larger domain in the model. Neither Bacillus alkaline phosphatase sequenced contains any cysteine residues, an amino acid implicated in intrachain disulfide bond formation in other alkaline phosphatases.
Assuntos
Fosfatase Alcalina/genética , Bacillus subtilis/enzimologia , Escherichia coli/enzimologia , Homologia de Sequência do Ácido Nucleico , Sequência de Aminoácidos , Sequência de Bases , Sítios de Ligação , Clonagem Molecular , DNA Bacteriano/genética , Dados de Sequência Molecular , Mutação , Plasmídeos , Conformação Proteica , Mapeamento por RestriçãoRESUMO
A model was developed to study the multiplication of various Legionella spp. in tap water containing Hartmannella vermiformis. Tap water cultures prepared with the following components were suitable for the multiplication studies: Legionella spp., 10(3) CFU/ml; H. vermiformis, 10(4.4) cysts per ml; and killed Pseudomonas paucimobilis, 10(9) cells per ml. Cocultures were incubated at 37 degrees C for at least 1 week. The following legionellae multiplied in tap water cocultures in each replicate experiment: L. bozemanii (WIGA strain), L. dumoffii (NY-23 and TX-KL strains), L. micdadei (two environmental strains), and L. pneumophila (six environmental strains and one clinical isolate). Growth yield values for these strains were 0.6 to 3.5 log CFU/ml. Legionellae which did not multiply in replicate cocultures included L. anisa (one strain), L. bozemanii (MI-15 strain), L. micdadei (a clinical isolate), L. longbeachae, (one strain), and L. pneumophila (Philadelphia 1 strain). L. gormanii and an environmental isolate of L. pneumophila multiplied in only one of three experiments. None of the legionellae multiplied in tap water containing only killed P. paucimobilis. The mean growth yield (+/- standard deviation) of H. vermiformis in the cocultures was 1.2 +/- 0.1 log units/ml. H. vermiformis supports multiplication of only particular strains of legionellae, some of which are from diverse origins.
Assuntos
Hartmannella/crescimento & desenvolvimento , Legionella/crescimento & desenvolvimento , Abastecimento de Água , Animais , Humanos , Cinética , Modelos Biológicos , Microbiologia da ÁguaRESUMO
In RBL-2H3 rat tumor mast cells, cross-linking the high affinity IgE receptor, Fc epsilon R1, activates the protein-tyrosine kinases Lyn and Syk and initiates a series of responses including protein-tyrosine phosphorylation, inositol 1,4,5-trisphosphate synthesis, Ca2+ mobilization, secretion, membrane ruffling, and actin plaque assembly. The development of chimeric receptors containing cytoplasmic domains of individual subunits of the heterotrimeric (alpha beta gamma 2) Fc epsilon R1 has simplified analyses of early signaling events in RBL-2H3 cells. Here, RBL-2H3 cells were transfected with cDNAs encoding the extracellular and transmembrane domains of the interleukin-2 receptor alpha subunit (the Tac antigen) joined to the C-terminal cytoplasmic domains of the Fc epsilon R1 gamma and beta subunits (TT gamma and TT beta). Both sequences contain tyrosine activation motifs implicated in antigen receptor signal transduction. TT gamma and TT beta are expressed independently of the native Fc epsilon R1, as demonstrated by the ability of Tac cross-linking agents to trigger the clustering and internalization through coated pits of both chimeric receptors without co-clustering the Fc epsilon R1. A full range of signaling activities is induced by TT gamma cross-linking; the TT gamma-induced responses are slower and, except for Lyn activation, smaller than the Fc epsilon R1-induced responses. In striking contrast, TT beta cross-linking elicits no tyrosine phosphorylation or signaling responses, it impairs basal activities measured in secretion and anti-PY (anti-phosphotyrosine antibody) immune complex kinase assays, and it antagonizes Fc epsilon R1-induced Lyn and Syk activation, protein-tyrosine phosphorylation, and signaling responses. We hypothesize that the isolated beta subunit binds a specific kinase or coupling protein(s) required for signaling activity, sequestering it from the signal-transducing gamma subunit. Binding the same kinase or coupling protein to the beta subunit of the intact Fc epsilon R1 may serve instead to present it to the adjacent gamma subunit, resulting in enhanced kinase activation and signaling responses.