Prevalence and pattern of contraceptive uptake among adolescents in an internally displaced camp, North Central, Nigeria.

Internally displaced Persons are marginally sidelined in many areas of life, reproductive health issues inclusive. There is a need to know the prevalence and pattern of contraceptive use among this vulnerable group of people. This study determined the prevalence and pattern of contraceptive uptake among internally displaced adolescents in North-Central Camp, Abuja, Nigeria. A descriptive cross-sectional study, among 403 adolescents using semi-structured questionnaires. The mean age of the respondents was 19.53±6.4 years and 21.34±7.34 years at first birth. Awareness about FP was high, (483, 95.0%), however, only 169 (41.9%) ever used a family planning method, while 82 (20.3%) were current users, 72 (42.6%) of the 169 ever users admitted to have used pills, while 44 (53.7%) of the 82 current users were using condom only. One third, 160 (39.7%), were pregnant, while 78 (19.4%) of those pregnant were unintentional, therefore the unintended pregnancy rate was 19.4%. Bivariate analysis revealed that respondents' use of contraceptive was significantly related to religion (<0.001), ethnic group (<0.001), marital status (<0.001), family type (<0.001), and educational attainment (<0.001). While respondents' knowledge of contraceptive was significantly associated with age (P<0.00000001), educational level (P<0.002), and ethnic group (P<0.001). The prevalence of contraceptive use among respondents was 20.3%, while 41.9% ever used a method. Pill was the major Family planning method ever used, while condom was mostly used by the current users.

Tuberculosis infection prevention and control measures in DOTS centres in Lagos State, Nigeria.

Nigeria is a high tuberculosis (TB) burden country. However, there is limited evidence on implementation of tuberculous infection prevention and control (TBIC) practices in Nigeria. To assess TBIC practices, and barriers to their implementation, in TB-DOTS centres in Lagos State, Nigeria. A descriptive cross-sectional study was used to assess 112 TB-DOTS centres in primary and secondary health facilities in Lagos State using mixed methods. Quantitative data comprised a survey and measurement of the air exchange rate in a subsample of centres. The qualitative aspect comprised focus-group discussions to highlight health care workers' (HCWs') perceptions of TBIC guidelines and barriers to their implementation. The majority of the DOTS centres had a dedicated TBIC officer, while a fifth (21%) had documented TBIC plans. About 57% of DOTS centres had staff that had been trained on TBIC and 37% provided some form of personal respiratory protection (face masks/tissue papers) for staff or patients. The air exchange rate was adequate in 21% of centres. The HCWs' perception of being at risk of contracting TB was reported to affect the way they relate to TB patients. The key barrier to implementing TBIC was the design of DOTS centres. TBIC measures at study centres were inadequate. Institutional commitment, renovation of existing and appropriate design of new DOTS centres in the future to improve TBIC implementation is recommended. .

Antihypertensive use, prescription patterns, and cost of medications in a Teaching Hospital in Lagos, Nigeria.

INTRODUCTION: Hypertension has been reported as the strongest modifiable risk factor for cardiovascular morbidity and mortality. AIMS: The aim of the study was to identify the most prescribed antihypertensive drugs, its patterns, comorbidities, cost of medications, and laboratory investigations. SETTINGS AND DESIGN: This study was a cross-sectional, descriptive study of hypertensive patients conducted at the Lagos State University Teaching Hospital, Ikeja. SUBJECTS AND METHODS: A total of 200 case notes were retrieved from the medical records unit over a period of 8 weeks. Information on antihypertensive prescriptions and comorbidities was retrieved. The average cost of medications and laboratory investigations was calculated. Statistical Analysis Tool Used: SPSS software version 16. RESULTS: The mean age of the patients was 58.44 ± 12.65 years. Of the 200 patients, 5 (2.5%) were on monotherapy and 195 (97.5%) were on combination therapy. One hundred and twenty (60%) patients had comorbidities which included congestive heart failure 55 (27.5%), diabetes mellitus 22 (11%), hyperlipidemia 15 (7.5%), and cardiovascular disease 13 (6.5%). The various classes of antihypertensive drugs prescribed were diuretics 128 (64.0%), beta-blockers 126 (63.0%), calcium channel blockers 106 (53.0%), angiotensin-converting enzymes inhibitors 103 (51.5%), angiotensin receptor blockers 33 (16.5%), alpha blockers 9 (4.5%), and fixed drug combinations 2 (1.0%). The average cost per month of the antihypertensive medications was ₦ 2045 (US$10.2). CONCLUSIONS: Antihypertensive prescription pattern was in accordance with the seventh report of Joint National Committee on Prevention, Detection, Evaluation, and Treatment of high blood pressure. Community-based insurance scheme should be encouraged and effective implementation of integrated noncommunicable diseases screening into the primary health care services would be helpful.

Tuberculosis infection control measures in health care facilities offering tb services in Ikeja local government area, Lagos, South West, Nigeria.

BACKGROUND: Tuberculosis infection among health care workers is capable of worsening the existing health human resource problems of low--and middle-income countries. Tuberculosis infection control is often weakly implemented in these parts of the world therefore, understanding the reasons for poor implementation of tuberculosis infection control guidelines are important. This study was aimed at assessing tuberculosis infection control practices and barriers to its implementation in Ikeja, Nigeria. METHODS: A cross-sectional study in 20 tuberculosis care facilities (16 public and 4 private) in Ikeja, Lagos was conducted. The study included a facility survey to assess the availability of tuberculosis infection control guidelines, the adequacy of facilities to prevent transmission of tuberculosis and observations of practices to assess the implementation of tuberculosis infection control guidelines. Four focus group discussions were carried out to highlight HCWs' perceptions on tuberculosis infection control guidelines and barriers to its implementation. RESULTS: The observational study showed that none of the clinics had a tuberculosis infection control plan. No clinic was consistently screening patients for cough. Twelve facilities (60%) consistently provided masks to patients who were coughing. Ventilation in the waiting areas was assessed to be adequate in 60% of the clinics while four clinics (20%) possessed N-95 respirators. Findings from the focus group discussions showed weak managerial support, poor funding, under-staffing, lack of space and not wanting to be seen as stigmatizing against tuberculosis patients as barriers that hindered the implementation of TB infection control measures. CONCLUSION: Tuberculosis infection control measures were not adequately implemented in health facilities in Ikeja, Nigeria. A multi-pronged approach is required to address the identified barriers to the implementation of tuberculosis infection control guidelines.

Exploratory analysis of the visceral disease subgroup in a phase III study of abiraterone acetate in metastatic castration-resistant prostate cancer.

BACKGROUND: Visceral disease, non-nodal soft-tissue metastases predominantly involving the lung and liver, is a negative prognostic factor in patients with metastatic castration-resistant prostate cancer (mCRPC). An exploratory analysis of COU-AA-301 assessed whether abiraterone acetate (AA) improved overall survival (OS) in mCRPC patients with visceral disease progressing post docetaxel. METHODS: In COU-AA-301, post-docetaxel mCRPC patients were randomized 2:1 to AA 1000 mg (n=797) or placebo (n=398) once daily, each with prednisone 5 mg b.i.d. The primary end point was OS; secondary end points included radiographic progression-free survival (rPFS), PSA response rate and objective response rate (ORR). Treatment effects in visceral disease (n=352) and non-visceral disease (n=843) subsets were examined using final data (775 OS events). RESULTS: AA plus prednisone produced similar absolute improvement in median OS in patients with (4.6 months) and without (4.8 months) visceral disease versus prednisone; hazard ratios (HRs) were 0.79 (95% confidence interval (CI): 0.60-1.05; P=0.102) and 0.69 (95% CI: 0.58-0.83; P<0.0001), respectively. Treatment with AA plus prednisone significantly and comparably improved secondary endpoint outcomes versus prednisone in both the subsets: the HRs for rPFS were 0.60 (95% CI: 0.46-0.78; P=0.0002) and 0.68 (95% CI: 0.58-0.80; P<0.0001) in visceral and non-visceral disease subsets, respectively. PSA response rates were 28% versus 7% in the visceral disease subsets and 30% versus 5% in the non-visceral disease subsets (both P<0.0001), and ORRs were 11% versus 0% (P=0.0058) and 19% versus 5% (P=0.0010), respectively. The incidence of grade 3/4 adverse events was similar between the subsets and between the treatment arms in each subset. Adverse events related to CYP17 blockade were increased in the AA arms and were similar in patients with or without visceral disease. CONCLUSIONS: AA plus prednisone provides significant clinical benefit, including improvements in OS and secondary end points, in post-docetaxel mCRPC patients with or without baseline visceral disease. The presence of visceral disease does not preclude clinical benefit from abiraterone.

Health workers sensitization: effects on perceived quality of immunization services among mothers of under five children in Ilorin, North Central Nigeria.

Clients' satisfaction with services received is an important dimension of evaluation that is examined only rarely in developing countries. Health care professionals have always acknowledged that satisfying the consumers at some level is essential to providing services of high quality. This is a quasi-experimental study. The study group included 150 mothers bringing their children for immunization at Alanamu Health Centre, Ilorin. The control group included 150 mothers bringing their children for immunization at Okelele Health Centre. Total population of mothers bringing their children for vaccines against tuberculosis/poliomyelitis/hepatitis B (BCG/ OPV/HBV) and against diphterite-pertussis-tetanus (DPT)/OPV/ HBV were recruited sequentially until sample size was attained. Mean waiting time at pre-intervention was 82.7 +/- 32.5 and 90.4 +/- 41.7 minutes for the study and control groups respectively. Post intervention, there was a significant decrease (p < 0.05) in the estimated waiting time in the study group (mean = 48.0 +/- 24.4 minutes) while there was no observed difference in the control p > 0.05 (mean = 88.4 +/- 40.6 minutes). Perceived adequacy of information on services being provided by the health facility was low (58%) in the study group while it was relatively higher in the control group (80%) but there was a significant increase in proportion of those that felt information was adequate only in the study group (p < 0.05) at post intervention. Waiting time in health facilities by clients should be reduced as this may give clients a positive perception of the service they have come to access. Information dissemination to clients should be encouraged among health workers as this would affect clients' knowledge and also quality of health care delivery.

Neutral endopeptidase inhibits prostate cancer tumorigenesis by reducing FGF-2-mediated angiogenesis.

Neutral endopeptidase (NEP) is a cell surface peptidase that catalytically inactivates a variety of physiologically active peptides including basic fibroblast growth factor (FGF-2). We investigated the effect of using lentivirus to overexpress NEP in NEP-deficient DU145 prostate cancer cells. Third-generation lentiviral vectors encoding wild-type NEP (L-NEP), catalytically inactive mutant NEP (L-NEPmu), and green fluorescent protein (L-GFP) were stably introduced into DU145 cells. FGF-2 levels in cell culture supernatants decreased by 80% in L-NEP-infected DU145 cells compared to cells infected with L-NEPmu or L-GFP (P<0.05) while levels of other angiogenic factors were not altered. In vitro tubulogenesis of human vascular endothelial cells induced by conditioned media from DU145 cells infected with L-NEP was significantly reduced compared with that from DU145 cells infected with L-GFP (P<0.05). Tumor xenografts from L-NEP-infected DU145 cells were significantly smaller compared to control cell xenografts and vascularity within these tumors was decreased (P<0.05). Our data suggest that stable expression of NEP in DU145 cells inhibits prostate cancer tumorigenicity by inhibiting angiogenesis, with a probable mechanism being proteolytic inactivation of FGF-2.

Lentiviral vector neutral endopeptidase gene transfer suppresses prostate cancer tumor growth.

Neprilysin (neutral endopeptidase, NEP) is a cell surface peptidase whose expression is lost in approximately 50% of prostate cancers (PC). NEP normally functions to inactivate peptides such as bombesin and endothelin-1, and potentiates the effects of the PTEN tumor suppressor via a direct protein-protein interaction. NEP loss contributes to PC progression. We investigated the therapeutic efficacy of using a lentiviral vector system to restore NEP expression in PC cells. Third-generation lentiviral vectors encoding wild-type NEP (L-NEP) or green fluorescent protein (L-GFP) were introduced into NEP-deficient 22RV1 PC cells. Cells infected with L-NEP or L-GFP at a multiplicity of infection of 10 demonstrated NEP enzyme activity of 1171.2+/-4.9 and 17.2+/-5.3 pmol/microg/min (P<0.0001), respectively. Cell viability, proliferation and invasion were each significantly inhibited in 22RV1 cells expressing NEP compared with control cells infected with L-GFP (P<0.01). Analysis of known downstream effects of NEP showed NEP-expressing cells exhibiting decreased Akt and focal adhesion kinase phosphorylation and increased PTEN protein expression. Finally, injection of L-NEP into established 22RV1 xenograft tumors significantly inhibited tumor growth (P<0.01). These experiments demonstrate that lentiviral NEP gene transfer is a novel targeted strategy for the treatment of NEP-deficient PC.

Neuropeptide-stimulated cell migration in prostate cancer cells is mediated by RhoA kinase signaling and inhibited by neutral endopeptidase.

The neuropeptides bombesin and endothelin-1 stimulate prostate cancer (PC) cell migration and invasion (J Clin Invest, 2000; 106: 1399-1407). The intracellular signaling pathways that direct this cell movement are not well delineated. The monomeric GTPase RhoA is required for migration in several cell types including neutrophils, monocytes and fibroblasts. We demonstrate that bombesin-stimulated PC cell migration occurs via the heterotrimeric G-protein-coupled receptors (G-protein) G alpha 13 subunit leading to activation of RhoA, and Rho-associated coiled-coil forming protein kinase (ROCK). Using siRNA to suppress expression of the three known G-protein alpha-subunit-associated RhoA guanine nucleotide exchange factors (GEFs), we also show that two of these RhoA GEFs, PDZ-RhoGEF and leukemia-associated RhoGEF (LARG), link bombesin receptors to RhoA in a non-redundant manner in PC cells. We next show that focal adhesion kinase, which activates PDZ-RhoGEF and LARG, is required for bombesin-stimulated RhoA activation. Neutral endopeptidase (NEP) is expressed on normal prostate epithelium whereas loss of NEP expression contributes to PC progression. We also demonstrate that NEP inhibits neuropeptide activation of RhoA. Together, these results establish a contiguous signaling pathway from the bombesin receptor to ROCK in PC cells, and they implicate NEP as a major regulator of neuropeptide-stimulated RhoA in these cells. This work also identifies members of this signaling pathway as potential targets for rational pharmacologic manipulation of neuropeptide-stimulated migration of PC cells.

Activation of p300 histone acetyltransferase activity and acetylation of the androgen receptor by bombesin in prostate cancer cells.

Androgen receptor signaling in prostate cancer cells is augmented by the androgen receptor (AR) coactivator p300, which transactivates and acetylates the AR in the presence of dihydrotestosterone (DHT). As prostate cancer (PC) cells progress to androgen independence, AR signaling remains intact, indicating that other factors stimulate AR activities in the absence of androgen. We previously reported that neuropeptide growth factors could transactivate the AR in the presence of very low concentrations of DHT. Here, we examine the involvement of p300 in neuropeptide activation of AR signaling. Transfection of increasing concentrations of p300 in the presence of bombesin into PC-3 cells resulted in a linear increase in AR transactivation, suggesting that p300 acts as a coactivator in neuropeptide-mediated AR transactivation. P300 is endowed with histone acetyltransferase (HAT) activity. Therefore, we examine the effect of bombesin on p300 HAT activity. At 4 h after the addition of bombesin, p300 HAT activity increased 2.0-fold (P<0.01). Incubation with neutral endopeptidase, which degrades bombesin, or bombesin receptor antagonists blocked bombesin-induced p300 HAT activity. To explore the potential signaling pathways involved in bombesin-induced p300 HAT activity, we examined Src and PKCdelta pathways that mediate bombesin signaling. Inhibitors of Src kinase activity or Src kinase siRNA blocked bombesin-induced p300 HAT activity, whereas PKCdelta inhibitors or PKCdelta siRNA significantly increased bombesin-induced p300 HAT activity suggesting that Src kinase and PKCdelta kinase are involved in the regulation of p300 HAT activity. As AR is acetylated in the presence of 100 nM DHT, we next examined whether bombesin-induced p300 HAT activity would result in enhanced AR acetylation. Bombesin-induced AR acetylation at the same motif KLKK observed in DHT-induced acetylation. Elimination of p300 using p300 siRNA reduced AR acetylation, demonstrating that AR acetylation was mediated by p300. AR acetylation results in AR transactivation and the expression of the AR-regulated gene prostate-specific antigen (PSA). Therefore, we examined bombesin-induced AR transactivation and PSA expression in the presence and absence of p300 siRNA and found inhibition of p300 expression reduced bombesin-induced AR transactivation and PSA expression. Together these results demonstrate that bombesin, via Src and PKCdelta signaling pathways, activates p300 HAT activity which leads to enhanced acetylation of AR resulting in increased expression of AR-regulated genes.

Perception and attitude to epilepsy among teachers in primary, secondary and tertiary educational institutions in middle belt Nigeria.

Compared with the disability associated with repeated seizures or side-effects of antiepileptic medications, the social stigma associated with epilepsy is often a major handicap to people living with this condition. This study therefore looked at the knowledge, attitude and perception of teachers who see a lot of epileptics, relates on daily bases and have a high influence on students with epilepsy.Self-administered questionnaires were used to obtain information from 460 randomly selected teachers in primary, secondary and tertiary educational institutions in Kwara State-middle belt of Nigeria. The response rate was 75%. Almost all of the teachers had heard about epilepsy, but their awareness does not equate with the acceptance and understanding of epilepsy. About 30.5% believed that it could be contracted through the saliva of an epileptic, 27.7% thought it was synonymous with possession with evil spirit, while 10% misunderstood epilepsy for insanity. Close to one-fifth of the teachers were of the opinion that epileptic students have a below average mental capacity compared with other students and so cannot attainment the highest possible education. Negative attitude and bias towards epilepsy is still deeply ingrained among teachers in Nigeria. Apart from formal education, teachers need to have health education courses on common disease conditions such as epilepsy that are prevalent in school age. This might help to reduce prejudice and increase the acceptance of epileptic individuals into the classroom.

Permanent hypoparathyroidism developing post-thyroidectomy.

A case of permanent hypocalcaemia following a subtotal thyroidectomy for a simple multinodular goiter in a 35 year -- old married teacher is presented. This further confirms the need for utmost precaution during thyroid surgery to prevent the damage or inadvertent removal of the parathyroid glands and its consequential complications. It also throws more light on the problem faced in the management of hypocalcaemia vis a vis patient compliance and availability of proper medications in this environment.

Arrestin/clathrin interaction. Localization of the clathrin binding domain of nonvisual arrestins to the carboxy terminus.

We have recently demonstrated that the nonvisual arrestins, beta-arrestin and arrestin3, interact with high affinity and stoichiometrically with clathrin, and we postulated that this interaction mediates internalization of G protein-coupled receptors (Goodman, O. B., Jr., Krupnick, J. G., Santini, F., Gurevich, V. V., Penn, R. B., Gagnon, A. W., Keen, J. H., and Benovic, J. L. (1996) Nature 383, 447-450). In this study, we localized the clathrin binding domain of arrestin3 using a variety of approaches. Truncation mutagenesis demonstrated that the COOH-terminal half of arrestin3 is required for clathrin interaction. Assessment of the clathrin binding properties of various glutathione S-transferase-arrestin3 fusion proteins indicated that the predominant clathrin binding domain is contained within residues 367-385. Alanine scanning mutagenesis further localized this domain to residues 371-379, and site-directed mutagenesis demonstrated the critical importance of both hydrophobic (Leu-373, Ile-374, and Phe-376) and acidic (Glu-375 and Glu-377) residues in the arrestin3/clathrin interaction. These results are complementary to the observation that hydrophobic and basic residues in clathrin are critical for its interaction with nonvisual arrestins (Goodman, O. B. , Jr., Krupnick, J. G., Gurevich, V. V., Benovic, J. L., and Keen, J. H. (1997) J. Biol. Chem. 272, 15017-15022). Lastly, an arrestin3 mutant in which Leu-373, Ile-374, and Phe-376 were mutated to Ala was significantly defective in its ability to promote beta2-adrenergic receptor internalization in COS-1 cells when compared with wild-type arrestin3. Taken together, these results implicate a discrete region of arrestin3 in high affinity binding to clathrin, an interaction critical for agonist-promoted internalization of the beta2-adrenergic receptor.

Arrestin/clathrin interaction. Localization of the arrestin binding locus to the clathrin terminal domain.

Previously we demonstrated that nonvisual arrestins exhibit a high affinity interaction with clathrin, consistent with an adaptor function in the internalization of G protein-coupled receptors (Goodman, O. B., Jr., Krupnick, J. G., Santini, F., Gurevich, V. V., Penn, R. B., Gagnon, A. W., Keen, J. H., and Benovic, J. L. (1996) Nature 383, 447-450). In this report we show that a short sequence of highly conserved residues within the globular clathrin terminal domain is responsible for arrestin binding. Limited proteolysis of clathrin cages results in the release of terminal domains and concomitant abrogation of arrestin binding. The nonvisual arrestins, beta-arrestin and arrestin3, but not visual arrestin, bind specifically to a glutathione S-transferase-clathrin terminal domain fusion protein. Deletion analysis and alanine scanning mutagenesis localize the binding site to residues 89-100 of the clathrin heavy chain and indicate that residues 1-100 can function as an independent arrestin binding domain. Site-directed mutagenesis identifies an invariant glutamine (Glu-89) and two highly conserved lysines (Lys-96 and Lys-98) as residues critical for arrestin binding, complementing hydrophobic and acidic residues in arrestin3 which have been implicated in clathrin binding (Krupnick, J. G., Goodman, O. B., Jr., Keen, J. H., and Benovic, J. L. (1997) J. Biol. Chem. 272, 15011-15016). Despite exhibiting high affinity clathrin binding, arrestins do not induce coat assembly. The terminal domain is oriented toward the plasma membrane in coated pits, and its binding of both arrestins and AP-2 suggests that this domain is the anchor responsible for adaptor-receptor recruitment to the coated pit.

Mapping of the molecular determinants involved in the interaction between eps15 and AP-2.

eps15, a substrate for the epidermal growth factor receptor and other receptor tyrosine kinases, possesses a discrete domain structure with protein-binding properties. It interacts with a number of cellular proteins through an evolutionarily conserved protein-binding domain, the eps15 homology domain, located in its NH2-terminal region. In addition, a proline-rich region, located in the COOH-terminal portion of eps15, can bind to the Src homology 3 domain of the crk proto-oncogene product in vitro. Recently, coimmunoprecipitation between eps15 and AP-2, a major component of coated pits, was reported. Here, we characterize the molecular determinants of the eps15/AP-2 interaction. The AP-2 binding region of eps15 is localized in its COOH-terminal region and spans approximately 80 amino acids. At least three molecular determinants, located at residues 650-660, 680-690, and 720-730, are involved in the binding. AP-2 binds to eps15 through its alpha subunit (alpha-adaptin); in particular, the COOH-terminal region of alpha-adaptin, the so-called alpha-ear, contains the eps15 binding region.

Beta-arrestin acts as a clathrin adaptor in endocytosis of the beta2-adrenergic receptor.

The ability of a system to regulate its responsiveness in the presence of a continuous stimulus, often termed desensitization, has been extensively characterized for the beta2-adrenergic receptor (beta2AR). beta2AR signalling is rapidly attenuated through receptor phosphorylation and subsequent binding of the protein beta-arrestin. Ultimately the receptor undergoes internalization, and although the molecular mechanism is unclear, receptor phosphorylation and beta-arrestin binding have been implicated in this processs. Here we report that beta-arrestin and arrestin-3, but not visual arrestin, promote beta2AR internalization and bind with high affinity directly and stoichiometrically to clathrin, the major structural protein of coated pits. Moreover, beta-arrestin/arrestin chimaeras that are defective in either beta2AR or clathrin binding show a reduced ability to promote beta2AR endocytosis. Immunofluorescence microscopy of intact cells indicates an agonist-dependent colocalization of the beta2AR and beta-arrestin with clathrin. These results show that beta-arrestin functions as an adaptor in the receptor-mediated endocytosis pathway, and suggest a general mechanism for regulating the trafficking of G-protein-coupled receptors.

The alpha chain of the AP-2 adaptor is a clathrin binding subunit.

We have utilized a rabbit reticulocyte lysate coupled transcription-translation system to express the large subunits of the clathrin associated protein-2 (AP-2) complex so that their individual functions may be studied separately. Appropriate folding of each subunit into N-terminal core and C-terminal appendage domains was confirmed by limited proteolysis. Translated beta 2 subunit bound to both assembled clathrin cages and immobilized clathrin trimers, confirming and extending earlier studies with preparations obtained by chemical denaturation-renaturation. Translated alpha a exhibited rapid, reversible and specific binding to clathrin cages. As with native AP-2, proteolysis of alpha a bound to clathrin cages released the appendages, while cores were retained. Further digestion revealed a approximately 29-kDa alpha a clathrin-binding fragment that remained tightly cage-associated. Translated alpha a also bound to immobilized clathrin trimers, although with greater sensitivity to increasing pH than the translated beta 2 subunit. Clathrin binding by both the alpha and beta subunits is consistent with a bivalent cross-linking model for lattice assembly (Keen, J. H. (1987) Cell Biol. 105, 1989). It also raises the possibility that the alpha-clathrin interaction may have other consequences, such as modulation of lattice stability or shape, or other alpha functions.