Biological effects of targeted inactivation of hepatocyte growth factor-like protein in mice

Hepatocyte growth factor-like protein (HGFL) is a liver-derived serum glycoprotein involved in cell proliferation and differentiation, and is proposed to have a fundamental role in embryogenesis, fertility, hematopoiesis, macrophage activation, and tissue repair. To assess the in vivo effects of total loss of HGFL, we generated mice with targeted disruption of the gene resulting in loss of the protein. Disruption of the HGFL gene allowed for normal embryogenesis, and followed a Mendelian pattern of genetic transmission. Mice homozygous for the targeted allele (HGFL-/- mice) are fertile, and grow to adulthood without obvious phenotypic abnormalities in unchallenged animals, except for development of lipid-containing cytoplasmic vacuoles in hepatocytes throughout the liver lobules. These histologic changes are not accompanied by discernible changes in synthetic or excretory hepatic functions. Hematopoiesis appears unaltered, and although macrophage activation is delayed in the absence of HGFL, migration to the peritoneal cavity upon challenge with thioglycollate was similar in HGFL-/- and wild-type mice. Challenged with incision to skin, HGFL-/- mice display normal wound healing. These data demonstrate that HGFL is not essential for embryogenesis, fertility, or wound healing. HGFL-deficient mice will provide a valuable means to assess the role of HGFL in hepatic and systemic responses to inflammatory and infectious stimuli in vivo.

Standard dose Gd-DTPA dynamic MR of renal arteries

Renal MR contrast enhancement depends on the timing of image acquisition. Limited human trials have demonstrated efficacy of renal artery stents on salvage of renal function. This study assessed the ability of dynamic gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) administration to demonstrate renal artery stenosis and renal stent patency compared to conventional angiography as the gold standard. Twenty subjects referred for renal angiography underwent 22 dynamic MR studies, including 7 with renal artery stenting (Palmaz P204 or P201, Johnson & Johnson, Sydney, Australia). All were examined with conventional angiography and after dynamic Gd-DTPA infusion. Coronal MR images of the kidneys were acquired using a GE Signa 1.5-T magnet (General Electric Medical Systems, Milwaukee, WI) (fast spoiled gradient echo [FSPGR]; TE=4.2 msec, TR=68-150 msec, flip angle=75 degrees) 0 to 600 seconds after iv bolus injection of 15 ml of Gd-DTPA during sequential breath-hold acquisitions, 13 to 32 seconds each. All 51 renal arteries (13 stenosed, 38 normal) were detected with dynamic MRI. Severity of renal artery stenosis was classified correctly with an accuracy of 98% (95% confidence interval [CI]: 85-100), yielding 98% specificity and 100% sensitivity. All nine renal stents were visualized with 100% accurate patency documentation. FSPGR MRI with bolus Gd-DTPA administration can provide adequate time and spatial resolution to demonstrate renal artery stenosis.

Hereditary hemochromatosis. Preventing chronic effects of this underdiagnosed disorder

Hereditary hemochromatosis, once thought to be rare, is the most common genetic disorder in the United States. Nonetheless, the condition often goes undetected and untreated until its severe effects have become apparent. What clues can lead you to the diagnosis, and how can you spot them in your patients, before significant morbidity has occurred? In this article, Drs McDonnell and Witte discuss the diagnosis and management of this underrecognized problem as well as the various issues involved in screening. An illustrative case of hemochromatosis is also included.

Targeted overexpression of IGF-I evokes distinct patterns of organ remodeling in smooth muscle cell tissue beds of transgenic mice

Smooth muscle cells (SMC) of the vascular wall, bladder, myometrium, and gastrointestinal and respiratory tracts retain the ability to proliferate postnatally, which enables adaptive responses to injury, hormonal, or mechanical stimulation. SMC growth is regulated by a number of mesenchymal growth factors, including insulin-like growth factor I (IGF-I). To explore the function of IGF-I on SMC in vivo, the mouse SMC alpha-actin promoter fragment SMP8 (-1074 bp, 63 bp of 5'UT and 2.5 kb of intron 1) was cloned upstream of rat IGF-I cDNA, and the fusion gene microinjected to fertilized eggs of the FVB-N mouse strain. Mating of hemizygous mice with controls produced about 50% transgenic offspring, with equal sex distribution. Transgenic IGF-I mRNA expression was confined to SMC-containing tissues, with the following hierarchy: bladder > stomach > aorta = uterus > intestine. There was no transgene expression in skeletal muscle, heart, or liver. Radioimmunoassayable IGF-I content was increased by 3.5- to 4-fold in aorta, and by almost 10-fold in bladder of transgenic mice at 5 and 10 wk, with no change in plasma IGF-I levels. Wet weight of bladder, stomach, intestine, uterus, and aorta was selectively increased, with no change in total body or carcass weight of transgenic animals. In situ hybridization showed that transgene expression was exquisitely targeted to the smooth muscle layers of the arteries, veins, bladder, ureter, stomach, intestine, and uterus. Paracrine overproduction of IGF-I resulted in hyperplasia of the muscular layers of these tissues, manifesting in remarkably different phenotypes in the various SMC beds. Whereas the muscular layer of the bladder and stomach exhibited a concentric thickening, the SMC of the intestine and uterus grew in a longitudinal fashion, resulting in a marked lengthening of the small bowel and of the uterine horns. This report describes the first successful targeting of expression of any functional protein capable of modifying the phenotype of SMC in transgenic mice. IGF-I stimulates SMC hyperplasia, leading to distinct patterns of organ remodeling in the different tissue environments.

A submicroscopic deletion in Xq26 associated with familial situs ambiguus

Abnormal left-right-axis formation results in heterotaxy, a multiple-malformation syndrome often characterized by severe heart defects, splenic abnormalities, and gastrointestinal malrotation. Previously we had studied a large family in which a gene for heterotaxy, HTX1, was mapped to a 19-cM region in Xq24-q27.1. Further analysis of this family has revealed two recombinations that place HTX1 between DXS300 and DXS1062, an interval spanning approximately 1.3 Mb in Xq26.2. In order to provide independent confirmation of HTX1 localization, a PCR-based search for submicroscopic deletions in this region was performed in unrelated males with sporadic or familial heterotaxy. A cluster of sequence-tagged sites failed to amplify in an individual who also had a deceased, affected brother. FISH identified the mother as a carrier of the deletion, which arose as a new mutation from the maternal grandfather. The deletion interval spans 600-1,100 kb and lies wholly within the 1.3-Mb region identified by recombination. Discovery of this deletion supports localization of HTX1 to Xq26.2 and reveals the first molecular-genetic abnormality associated with human left-right-asymmetry defects.

Minor structural differences in Boc-CCK-4 derivatives dictate affinity and selectivity for CCK-A and CCK-B receptors

We previously reported novel Boc-CCK-4 (Boc-Trp-Met-Asp-Phe-NH2) derivatives possessing the general structure Boc-Trp-Lys[N epsilon-CO-NH-(R-Ph)]-Asp-Phe-NH2 (Shiosaki et al. J. Med. Chem. 1991, 34, 2837-2842). In contrast to Boc-CCK-4, which is 70-fold selective for the CCK-B receptor, the modified lysine-bearing tetrapeptides were highly potent and selective full agonists at the CCK-A receptor. Further investigation of the structure-activity profile following modification of the substituted phenylurea moiety appended off the lysine revealed that moving certain substituents, e.g. nitro or acetyl, from the 2- or 3-position on the phenyl ring to the 4-position, a relatively minor and subtle structural modification within the tetrapeptide, resulted in loss of CCK-A receptor selectivity and development of a trend toward CCK-B selectivity. These tetrapeptides, e.g. Boc-Trp-Lys[N epsilon-CO-NH-(4-NO2-Ph)]-Asp-Phe-NH2 and Boc-Trp-Lys[N epsilon-CO-NH-(4-Ac-Ph)]-Asp-Phe-NH2, were full agonists relative to CCK-8 in stimulating intracellular calcium mobilization in a cell line that expresses the CCK-B receptor.

Fibrolipomatous hamartoma: MR imaging findings

OBJECTIVE

To analyze the MR imaging features of fibrolipomatous hamartoma (FLH) of nerves.

DESIGN AND PATIENTS

MR imaging studies from six patients (three men and three women) were retrospectively reviewed by three musculoskeletal radiologists. In four patients, a biopsy of the nerve lesion was performed. In two patients, biopsy data were unavailable and the diagnosis was based on the clinical history combined with the MR imaging findings.

RESULTS AND CONCLUSION

MR imaging demonstrated fusiform nerve enlargement that was caused by fatty proliferation and thickening of nerve bundles. Nerve bundles appeared as serpentine tubular structures, hypointense on both T1- and T2-weighted images. The degree of fatty proliferation varied among patients. In addition, significant variation in the distribution of fat along the course of the nerves was noted. In three patients, FLH followed the branching pattern of the nerves, a characteristic pathologic finding. In two patients, intramuscular fat deposition (biceps and tibialis posterior muscles) was present. MR imaging findings of FLH are typical, allowing a confident diagnosis. The variation of fatty proliferation among patients and involved nerves as well as the tendency of the abnormalities to follow the branching pattern of the nerves is well demonstrated with MR imaging. FLH may present as an isolated nerve lesion, may be associated with intramuscular fat deposition, or may occur as a feature of macrodystrophia lipomatosa (MDL).

Immunohistological characteristics of T cell infiltrates in different forms of childhood onset chronic arthritis

OBJECTIVE

To characterize synovial T cell infiltrate, in terms of CD4/CD8 ratio and level of activation of T cells, in juvenile rheumatoid arthritis (JRA) and juvenile spondyloarthropathy(JSpA), to correlate these findings with clinical outcomes of the different forms of disease, and to compare them with findings in adult RA synovium.

METHODS

We studied synovial tissue specimens from 22 individuals with childhood onset of chronic arthritis (12 polyarticular JRA, 5 pauciarticular JRA, 5 JSpA) and 4 with adult RA. Specimens were selected from an initial bank from 40 patients on the basis of significant inflammation on hematoxylin and eosin and CD3 and CD68 monoclonal antibody staining (T cells and macrophages, respectively). Indirect immunohistochemistry was used with monoclonal antibodies to CD3, CD4, CD8, and interleukin 2 receptor alpha to determine CD4/CD8 ratios and the levels of activation within the T cell subsets. The distribution of gamma delta T cells was also studied.

RESULTS

Two patterns of T cell infiltration were seen. The majority of patients had lymphocytic aggregates associated with diffuse infiltrates; a few tissue specimens had diffuse infiltrates without aggregates. The CD4/CD8 ratio was significantly lower in pauciarticular course JRA than polyarticular JRA (p < 0.01) and RA (p < 0.05). Similarly patients with JSpA had a significantly lower CD4/CD8 ratio than patients with polyarticular JRA (P < 0.05). The level of T cell activation (CD3+IL-2R+) was significantly higher in pauciarticular compared with both polyarticular JRA (P < 0.01) and RA (p < 0.05). In general, higher levels of activation of CD8 cells than CD4 cells were seen, particularly in the pauciarticular JRA and JSpA groups. gamma delta T cells were prominent in 2 patients.

CONCLUSION

Demonstrated differences in T cell subset distribution between types of childhood chronic arthritis at a histopathological level may reflect different pathogenic mechanisms.

Regulated expression of complement factor B in the human kidney

We have previously demonstrated regulated expression of C3 in the proximal renal tubular epithelial cells of humans. To test the hypothesis that local alternative pathway complement activation could contribute to the tubulointerstitial component of chronic renal disease, we examined factor B gene expression in human kidneys. 35S riboprobes were generated from a human factor B cDNA. By in situ hybridization, proximal tubular factor B message was seen in 17 kidneys with various nephropathies. The expression was most intense in organs with evidence of interstitial inflammation, and its localization paralleled the inflammation. As was the case with C3 and C4, there was never any evidence of glomerular factor B message, nor was any seen in infiltrating inflammatory cells. In eight normal kidney tissues, factor B expression was either absent or restricted to rare foci of interstitial infiltration. The proximal renal tubular epithelium of humans appears to express the genes for both components of the alternative pathway convertase, C3 and factor B. These locally produced components may be important mediators of the interstitial inflammation that is common to all progressive nephritides.

[Results after coronary bypass operation]

OBJECTIVE

To determine the influence of various risk factors on 30-day postoperative mortality rate of aortocoronary bypass operation at different centres.

PATIENTS AND METHODS

Data on 227 patients (179 men, mean age 63 [40-87] years; 48 women, mean age 68 [44-81] years), 219 first operations, 8 second operations) were retrospectively analysed. In all patients the indications for aortocoronary bypass surgery had been established in the last 3 months of 1993. The operations had been performed at six cardiac centres in Germany (five in Hessen [H1-H5]) and in three hospitals elsewhere in Europe outside of Germany (E1-E3).

RESULTS

The operative mortality was relatively high (5.3%), 152 patients (67%) presenting with one or more risk factors accounting for an increased perioperative mortality. The mortality rate was significantly higher for: clearly impaired left ventricular function (ejection fraction < 40%): 20 vs 3% with an ejection fraction > or = 40% (P < 0.001); emergency operation: 16.6 vs 2.7% for elective operation (P < 0.001); advanced age (> or = 70 years): 10.9 vs 3.1% for younger patients (P < 0.025); and unstable angina: 9.2 vs 2.9% with stable angina (P < 0.05). Most of the bypasses were done with the internal mammary artery (63.9%, usually combined with venous bypasses (exclusive use of venous bypasses in 35.2%), but the proportion of arterial bypasses differed greatly between centres (96% in H3, 19% in H4).

CONCLUSIONS

(1) Aortocoronary bypass operations are done on many patients with important risk factors, resulting in a relatively high 30-day postoperative mortality rate. (2) The proportion of internal mammary artery bypasses markedly differs between centres in Hessen.

Turnover and distribution of intravenously administered mannose-terminated human acid beta-glucosidase in murine and human tissues

Gaucher disease type 1, the most prevalent lysosomal storage disease, is caused by the defective activity of the lysosomal enzyme, acid beta-glucosidase, or glucocerebrosidase. Infusion of purified acid beta-glucosidase containing alpha-mannosyl-terminated oligosaccharides (alglucerase) is efficacious in reversing hematologic, hepatic, splenic, and bony disease manifestations. The murine tissue distribution and turnover of bolus injections of alglucerase was evaluated by enzymatic activity, quantitative cross-reacting immunologic material analyses, and immunofluorescence studies. Enzyme activity measurements detected distribution to liver, spleen, thymus, kidney, and bone marrow mononuclear cells, but not to lungs and brain. In kidney and thymus, the enzyme was transiently present. In liver and spleen, enzyme activity peaked at about 20 min postinjection followed by a biphasic decrease with t1/2 approximately 40-60 min and approximately 12-14 h. In bone marrow maximal enzyme activity was at 40-60 min with a disappearance t1/2 approximately 60 min. Quantitative cross-reacting immunologic material studies of liver and spleen showed delivery of enzyme with decreased catalytic rate constants whose degradation included denaturation and proteolytic components. By immunofluorescence the human enzyme was distributed primarily to reticuloendothelial cells of the liver and spleen. In autopsy material from a Gaucher disease type 2 patient treated with enzyme, immunohistochemical and activity studies showed distributions similar to those in mice. These studies indicate a complex delivery and intracellular degradation of acid beta-glucosidase with lower intrinsic activity than the administered therapeutic agent.

ABT-431: the diacetyl prodrug of A-86929, a potent and selective dopamine D1 receptor agonist: in vitro characterization and effects in animal models of Parkinson's disease

(-)-Trans 9,10-hydroxy-2-propyl-4,5,5a,6,7,11b-hexahydro-3-thia-5- azacyclopent-1-ena[c]phenanthrene hydrochloride (A-86929) is a potent and selective full agonist at the dopamine (DA) D1-like receptor. Judging by its binding affinities to the D1 and D2 classes of receptors, the compound is approximately 20-fold D1 receptor-selective, whereas relative potencies based on functional in vitro assays indicate that A-86929 is greater than 400-fold D1-selective. A-86929 has moderate to weak (Ki > 1 microM) affinity at other monoaminergic and peptidergic receptors, at ion channels and at monoamine uptake sites. The catechol of A-86929 was bis-acetylated to produce the prodrug, (-)-trans 9,10-acetoxy-2-propyl-4,5,5a,6,7,11-b-hexahydro-3-thia- 5-azacyclopent-1-ena[c]phenanthrene hydrochloride (ABT-431), which is more chemically stable yet is rapidly converted to the parent compound with a half-life of less than 1 min in plasma. Both A-86929 and ABT-431 produced contralateral rotation in rats bearing unilateral 6-hydroxydopamine lesions, with ED50 values of 0.24 mumol/kg s.c. and 0.54 mumol/kg s.c., respectively. A-86929 and ABT-431 improved behavioral disability scores and increased locomotor activity in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned marmoset model of Parkinson's disease in a dose-dependent manner (the minimum effective dose was 0.10 mumol/kg s.c.). When administered three times daily for 30 consecutive days to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned marmosets, A-86929 significantly improved disability scores throughout the duration of the study. Current Parkinson's disease therapy includes L-dopa, which stimulates both classes of DA receptors by virtue of its conversion to DA in vivo, and direct-acting D2-selective agonists. Stimulation of the D2 receptor, which is associated with all current DA agonist-based therapies, may contribute to their dose-limiting side effects. An agent such as A-86929 (or its prodrug ABT-431), which selectively stimulates the D1 receptor, may represent a novel mechanism for Parkinson's disease therapy with the potential for an improved side-effect profile and, consequently, improved patient compliance.

Functional dichotomy of neutral and acidic sphingomyelinases in tumor necrosis factor signaling

Ceramide produced by sphingomyelinases (SMases) has been recognized as an important second messenger in growth factor receptor signaling. Tumor necrosis factor (TNF), through binding to the 55 kDa TNF receptor (TNF-R55), rapidly activates two distinct types of SMase, a membrane-associated neutral (N-)SMase, and an endosomal acidic (A)-SMase. N-SMase and A-SMase are activated independently by different cytoplasmic domains of TNF-R55. Each type of SMase specifically couples to select pathways of TNF signaling. Ceramide generated by N-SMase directs the activation of proline-directed serine/threonine protein kinase(s) and phospholipase A2. In contrast, A-SMase triggers the activation of NF-kappa B. No apparent crosstalk was detected between N-SMase and A-SMase pathways, indicating that ceramide action depends on the topology of its production. These results suggest that N-SMase and A-SMase control important yet dissociable and nonoverlapping pathways of TNF receptor signal transduction.

Expression of the neural intermediate filament proteins peripherin and neurofilament-66/alpha-internexin in neuroblastoma

BACKGROUND

Peripherin and neurofilament (NF)-66/alpha-internexin are recently characterized, neuron-specific intermediate filament proteins that are expressed in the developing peripheral nervous system. Peripherin, in particular, is highly enriched in neuronal derivatives of the neural crest. We speculated that these intermediate filament proteins would be expressed in neuroblastoma (NB), a neural crest-derived tumor with many neuronal features.

EXPERIMENTAL DESIGN

By use of antibodies specific to peripherin and NF-66/alpha-internexin, we detected these proteins on Western blots of NB tissue extracts and in paraffin sections of NBs.

RESULTS

Western blotting indicated that NB tumor extracts contained immunoreactive proteins that co-migrated with rat peripherin and human NF-66/alpha-internexin from normal tissues, thus establishing the specificity of the antibodies for these proteins in tumors. The antibody specific for peripherin labeled all NBs, including immature NBs, composite ganglioneuroblastomas and ganglioneuromas. In contrast, the NF-66/alpha-internexin antibody labeled only 50% of NBs, and only weakly labeled most ganglioneuroblastomas and ganglioneuromas. Neither antibody labeled other small blue cell tumors such as lymphomas, rhabdomyosarcomas, Wilms' tumors, and Ewing sarcomas.

CONCLUSIONS

The specificity of the peripherin labeling of NB and the ability of the peripherin antibody to label the entire spectrum of NBs, including ganglioneuroblastomas and ganglioneuromas, indicate that this intermediate filament protein has potential as a diagnostic marker for these related neural crest neoplasms.

Involvement of episomal hpv31 in a laryngeal carcinoma - persistent episomal maintenance of hpv DNA after passage through nude-mice

We describe the involvement of HPV31 in a laryngeal carcinoma, a highly unusual anatomic site for this HPV subtype. In situ hybridization with a type-specific HPV probe identified infected tumor cells. Diagnostic Southern blot analysis confirmed that the HPV was type 31, and also revealed that the HPV DNA was episomal. The tumor was passaged in nude mice, and analysis of HPV DNA in the passaged tumor revealed that the viral DNA had persisted and that it had remained episomal. The status of p53 in the tumor was examined by Southern blots and by PCR analysis of a closely linked, highly polymorphic dinucleotide repeat region. There was no apparent allele loss or loss of heterozygosity at p53 or at the locus of another putative tumor suppressor gene at 17p distal to p53. To assess the integrity of the p53 gene in more detail, exons 4 through 11 were amplified by PCR, and the amplified DNA was directly sequenced. No mutations in p53 were observed, suggesting that other mechanisms such as sequestration of p53 by the E6 or E7 products may have contributed to the malignancy.

Ossification of the Achilles tendon: imaging abnormalities in 12 patients

Ossification of the Achilles tendon is a rare clinical entity that is characterized by the presence of an ossific mass contained within the fibrocartilaginous substance of the tendon. Because the radiographic features of this condition have not been documented entirely and the magnetic resonance (MR) imaging findings have not been determined, a review of 16 affected tendons in 12 patients was performed in an attempt to characterize the imaging abnormalities associated with this process. MR imaging was performed in three Achilles tendons which demonstrated thickening of the tendons at the level of the ossifications and a lack of intratendinous signal abnormalities compatible with acute tendinitis. Signal intensity similar to that of bone marrow was present in the ossifications.

The relationship of human papillomaviruses to anorectal neoplasia

This review begins with an overview of the anatomy of the anal canal, which is followed by a discussion of human papillomavirus (HPV) infections in the anogenital tract. The organization of the HPV genome and the function of the encoded proteins is discussed in relation to the oncogenic potential of these viruses. Particularly stressed are interactions with known tumor suppressor genes. Then the interaction of HPV with the host cells and some growth factors is reviewed. An important consideration is the synergy between this virus and other known carcinogenic factors. These include smoking, immunologic status, and other factors. Finally, the pathologic features of anal warts and malignant lesions are summarized with respect to their histologic findings and expression of viral subtypes.

Cholecystokinin antagonists: (R)-tryptophan-based hybrid antagonists of high affinity and selectivity for CCK-A receptors

The intriguing structural similarities of glutamic acid based cholecystokinin (CCK) antagonists (A-64718 and A-65186) and the benzodiazepine CCK antagonist MK-329 (L-364,718) have been reported. Efforts to include the weak CCK antagonist benzotript into this construct utilizing a similar approach have resulted in a novel series of benzotript-based hybrid antagonists N alpha-(3'-quinolylcarbonyl)-(R)-tryptophan di-n-pentylamide (9, A-67396), N alpha-(4',8'-dihydroxy-2'-quinolylcarbonyl)-(R)-tryptophan di-n-pentylamide (23, A-70276), and N alpha-(3'-quinolylcarbonyl)-(R)-5'-hydroxytryptophan di-n-pentylamide (36, A-71134) which possess respectively binding affinities of 23, 21, and 11 nM for the pancreatic CCK-A receptor and which inhibit CCK8-induced amylase secretion. Compound 9 possesses a selectivity of greater than 500-fold for the pancreatic CCK-A receptor over the CCK-B receptor.

Distinct requirements for activation at CCK-A and CCK-B/gastrin receptors: studies with a C-terminal hydrazide analogue of cholecystokinin tetrapeptide (30-33)

We describe here the properties of tert-butyloxycarbonyl-Trp-Leu-Asp-Phe-NHNH2 (A-57696), a C-terminal hydrazide analogue of tert-butyloxycarbonyl-CCK4 (Boc-Trp-Met-Asp-Phe-NH2), at four cholecystokinin (CCK) receptor-bearing tissues, the guinea pig pancreas and gall bladder (Type A), guinea pig cortex (Type B), and NCI-H345 cells, a human small cell lung cancer cell line that expresses CCK-B/gastrin receptors. Using 125I-Bolton-Hunter-cholecystokinin octapeptide (26-33) (125I-Bolton-Hunter-CCK8) as the radioligand, A-57696 was found to be selective for cortical CCK-B receptors (IC50 = 25 nM), compared with pancreatic CCK-A receptors (IC50 = 15 microM). A-57696 behaved as a competitive antagonist in reversing CCK8-stimulated pancreatic amylase secretion and phosphoinositide breakdown. By Schild analysis, its Kd was determined to be 4.7 and 6.8 microM in amylase and phosphoinositide assays, respectively. A-57696 (100 microM) did not elicit gall bladder contraction, and it inhibited contractions induced by CCK8. The Kd of A-57696 at gall bladder CCK-A receptors was 19 microM. In contrast, A-57696 behaved as a partial agonist (80% of maximal CCK8 response) in stimulating calcium mobilization at CCK-B/gastrin receptors on NCI-H345 cells. A-57696 and CCK8 inhibited each other in calcium mobilization experiments utilizing the fluorescent dye Indo-1. Stimulatory actions of CCK8 and A-57696 were reversed by the CCK-B-selective (R)-L-365,260 (100 nM), whereas at the same concentration, the CCK-A-selective (S)-L-365,260 was ineffective. Binding studies using 125I-Bolton-Hunter-CCK8 and 125I-gastrin indicated that binding sites labeled by these two ligands displayed similar affinities for CCK8, desulfated CCK8, gastrin, A-57696, and both enantiomers of L-365,260. A-57696 represents a new class of CCK-A peptide antagonist at guinea pig pancreas a new class of CCK-A peptide antagonist at guinea pig pancreas and gall bladder. Its contrasting functional activities at guinea pig CCK-A and CCK-B/gastrin receptors in a human tumor cell demonstrate that, in addition to the previously described differences in binding specificity for selective agonists and antagonists, CCK-A receptors and CCK-B/gastrin receptors have different requirements for activation.

Evidence for a complex regulatory array in the first intron of the human adenosine deaminase gene

Adenosine deaminase (ADA) is expressed ubiquitously by diverse mammalian cells and tissues but at levels that vary according to tissue and species. In humans, the thymus exhibits levels of the enzyme up to 100-fold higher than most other tissues. Using transgenic mice, we identified human ADA gene regulatory domains. Up to 3.7 kb of 5'-flanking and first exon DNA from the human ADA gene failed to promote the expression of a chloramphenicol acetyl transferase (CAT) reporter gene in an efficient, reproducible, or tissue-appropriate manner in transgenic mice. However, when 12.8 kb of DNA from the first intron of the human ADA gene was placed 3' of CAT-coding and -processing sequences, transgenic mice reproducibly expressed CAT activity in most tissues, with profoundly high levels in the thymus. DNase I hypersensitivity studies demonstrated that among transgenic mouse tissues, human thymus, and a variety of human cell lines, a region of the intron 4-10 kb downstream of the first exon exhibited an array of hypersensitive sites that varied according to tissue and cell type. Deletion of this region from the gene construction eliminated high-level expression in transgenic mice. In transfection-transient expression assays, the 12.8-kb intron fragment exhibited enhancer activity in several cell types. A 1.3-kb fragment encompassing two of the hypersensitive sites exhibited some of these activities. The results of these studies suggest that the diverse pattern of human ADA gene expression is determined, in part, by a cluster of cis-regulatory elements contained within its large first intron.