Role of monocytes and bacteria in Staphylococcus epidermidis endocarditis

The endocardial vegetation which is formed in the course of bacterial endocarditis (BE) contains tissue factor (TF)-dependent procoagulant activity. Earlier studies showed that monocytes are the main source of TF in the vegetations. The TF activity (TFA) of vegetations isolated from Streptococcus sanguis-infected rabbits depended on the numbers of bacteria as well as monocytes in the vegetation. In this study, we investigated whether for Staphylococcus epidermidis, a frequent pathogen in BE, an effect similar to that found for S. sanguis could be shown. In vitro, S. epidermidis was found to stimulate TFA of fibrin adherent monocytes significantly. This stimulation was maximal at a bacterium-to-monocyte ratio of 7. In vivo, TFA was found to be significantly higher in S. epidermidis-infected than in sterile catheter-induced vegetations. Reduction of vegetational bacterial numbers by teicoplanin treatment lead to a small but significant decrease of TFA. Reduction of monocyte numbers by etoposide did not affect vegetational TFA. Comparison of data for S. epidermidis and S. sanguis revealed that at equivalent bacterial numbers, vegetational TFAs were approximately the same for both microorganisms. Combining the results of the present study with those of a previous study using S. sanguis, we conclude that the main factor determining monocyte-dependent vegetational TFA is the number of vegetation-associated bacteria. The lower TFA found for S. epidermidis-infected than for S. sanguis-infected vegetations can be explained by the significantly lower bacterial numbers in the infected vegetations and consequently a lower stimulation of vegetation-associated monocytes.

Collaborating for international research development in Malawi, Africa

PURPOSE

To describe a collaborative research effort by a U.S. school of nursing, an African school of nursing, and the Malawian Ministry of Health. Providing assistance to women leaders in Malawi to develop and conduct research to improve the health of women and infants in villages is necessary.

SCOPE

This 5-year project, 1990-1995, included organizing a workshop on the research process, developing and testing pilot projects, developing and conducting two full-scale studies, and disseminating findings.

RESULTS

Two full-scale studies, one examining maternal mortality and one examining the effects of teen pregnancy, were completed with important health policy implications for Malawi.

CONCLUSIONS

Successful international collaborative research yields increased knowledge for all participants and important health information. International research requires continuous communication, people skilled in group work, sensitivity to cultural differences, patience, persistence, and commitment.

Mice transgenic for the human CGM6 gene express its product, the granulocyte marker CD66b, exclusively in granulocytes

The nonspecific cross-reacting antigen-95 (NCA-95/CD66b), is a member of the human carcinoembryonic antigen (CEA) family encoded by the CGM6 gene that is exclusively expressed in neutrophils and eosinophils. No murine counter-part is known to exist. We have analyzed a cosmid containing the complete CGM6 gene. The coding sequence is contained within six exons spanning a 16.5 kb region. The main transcriptional start site was mapped to a tight cluster between nucleotides -95 and -101 relative to the translational start site. As with other members of the CEA gene family, no typical TATA or CAAT-box sequences were found in the CGM6 gene. Transgenic mice were established with the cosmid insert. CD66b expression is first seen in the fetal liver on day 12.5 of mouse embryonic development, and it first appears in the bone marrow at day 17.5. Northern blot analysis showed that CD66b transcripts are confined to the bone marrow of adult mice, whereas immunohistochemistry also showed CD66b-positive granulocytes in the spleen, thymus, and lungs. FACScan analyses of bone marrow and spleen cells showed CD66b expression to be exclusive to granulocytes. Thus, all the elements necessary for regulating granulocyte-specific expression are present within this cosmid clone. These mice could provide a model for transplantation and for inflammation studies using CD66b as a granulocyte-specific marker.

Use of ECT for the inpatient treatment of recurrent major depression

OBJECTIVE

The authors' goals were to determine the frequency and distribution of ECT for general hospital inpatients with recurrent major depression and to estimate the effects of prompt ECT on the length and cost of inpatient care.

METHOD

Data from the 1993 Healthcare Cost and Utilization Project were analyzed to determine the rate of ECT use for adult inpatients with a principal discharge diagnosis of major depression, recurrent. Associations between prompt initial use of ECT (in the first 5 hospital days) and length and cost of inpatient care were examined before and after control for sociodemographic, diagnostic, and hospital organizational characteristics.

RESULTS

An estimated 9.4% of general hospital adult inpatients with a principal diagnosis of recurrent major depression received ECT in the survey year. A majority (59.2%) of these received their initial ECT session within the first 5 days after hospital admission. In univariate analyses, the likelihood of receiving ECT was greater for older patients, whites, privately insured individuals, and patients who lived in more affluent areas. Patients who received ECT tended to have relatively long and costly admissions. After control for several demographic, diagnostic, and hospital organizational characteristics, prompt ECT (as compared with delayed ECT or none) was associated with significantly shorter and less costly inpatient care.

CONCLUSIONS

The longer stays and higher treatment costs associated with ECT may be a consequence of patient selection. When patient selection is taken into account, prompt administration of ECT is associated with shorter and less costly hospital stays. Nonetheless, economically disadvantaged patients are relatively unlikely to receive this treatment.

cea5, a structurally divergent member of the murine carcinoembryonic antigen gene family, is exclusively expressed during early placental development in trophoblast giant cells

The carcinoembryonic antigen (CEA) gene family encodes a large family of glycoproteins. Some are probably involved in the homeostasis/development of epithelial cells and granulocyte activation, while others e.g. the pregnancy-specific glycoproteins, are expressed in the placenta and are essential for a positive outcome of pregnancy. In this paper, we have characterized cea5, a member of the murine CEA gene family. RNase protection and in situ hybridization analyses revealed that Cea5 mRNA is exclusively synthesized in primary and secondary trophoblast giant cells of the placenta only during early stages of development. Full-length Cea5 cDNA was obtained by a reverse transcription-polymerase chain reaction using day 10.5 post-coitum placental RNA. The 1.6-kilobase pair (kb) Cea5 mRNA encodes a secreted glycoprotein with a predicted size of 30 kDa. It is composed of a leader peptide (L), one immunoglobulin (Ig) variable or N, and one Ig constant-like or A domain. This domain organization is unique within the human and murine CEA families. Two overlapping cosmid clones covering 54 kb of the cea5 gene locus were mapped. cea5 consists of three exons (L, N, A/3'-untranslated region exon) located within a 4-kb region. rnCGM2, the rat cea5 counterpart, exhibits the same restricted expression pattern. This together with their exceptional conservation within the rat and murine CEA families and their absence from the human CEA family suggests that cea5 and rnCGM2 are of functional importance for rodent placental development.

The spatial genetic structure of cytoplasmic (cpDNA) and nuclear (allozyme) markers within and among populations of the gynodioecious Thymus vulgaris (Labiatae) in southern France

Recent advances in molecular biology have allowed the development of techniques to contrast spatial differentiation in nuclear and cytoplasmic genes and thus provide important data on relative levels of gene flow by pollen and seed in higher plants. In this paper, we compare the spatial structure of nuclear (allozymes) and cytoplasmic (cpDNA) genes among populations of the gynodioecious Thymus vulgaris in southern France. Based on a combination of three restriction enzymes (CfoI, EcoRV, and PstI), eight chlorotypes (combination of three restriction enzyme patterns revealed by Southern hybridization of Beta vulgaris cpDNA) were identified in the 13 studied populations. One chlorotype was particularly abundant and was detected in nearly all populations. Only one chlorotype was specific to a single population. Up to four different chlorotypes were observed in some populations. An FST of 0.238 (P < 0.002) for cpDNA haplotypes indicates spatial structure of cytoplasmic genes among the studied populations. Similar patterns were found within a single young population (CAB) structured in patches and surrounded by a continuous cover of T. vulgaris where the FST is 0.546 (P < 0.002). No significant correlation between sex and chlorotype nor between cpDNA diversity and female frequency was detected. Allozyme markers showed markedly less spatial structure (FST = 0.021 among populations and 0.019 in the CAB population, P < 0.001). This difference between cpDNA and nuclear allozyme markers suggests that pollen dispersal is more important than seed dispersal both among and within populations.

Evaluation of two live, cold-passaged, temperature-sensitive respiratory syncytial virus vaccines in chimpanzees and in human adults, infants, and children

Two live-attenuated, cold-passaged (cp), temperature-sensitive (ts) candidate vaccines, designated cpts530/1009 and cpts248/955, were attenuated, genetically stable, and immunogenic in chimpanzees and were highly attenuated for human adults. In respiratory syncytial virus (RSV)-seropositive children, cpts530/1009 was more restricted in replication than cpts248/955. In seronegative children, 10(4) pfu of cpts248/955 was insufficiently attenuated, and a high titer of vaccine virus was shed (mean peak titer, 10(4.4) pfu/mL), whereas 10(4) pfu of cpts530/1009 was relatively attenuated and restricted in replication (mean peak titer, 10(2.0) pfu/mL). At a dose of 10(5) pfu, cpts530/1009 was immunogenic in seronegative children (geometric mean titer of RSV neutralizing antibodies, 1:724). Transmission of either vaccine to seronegative placebo recipients occurred at a frequency of 20%-25%. Of importance, vaccine viruses recovered from chimpanzees and humans were ts. In contrast to previous studies, this study indicates that live attenuated RSV vaccines that are immunogenic and phenotypically stable can be developed. Additional studies are being conducted to identify a live RSV vaccine that is slightly more attenuated and less transmissible than cpts530/1009.

Delayed ulcer recurrence after gastric resection: a new postgastrectomy syndrome?

Recurrent ulceration following gastrectomy for peptic ulcer disease typically occurs within the first several years postoperatively. Since 1990, we have managed 20 patients who had undergone previous gastrectomy for peptic ulcer and developed ulcer recurrence more than 10 years postoperatively. Mean age at recurrence was 64 years, and the average time from original surgery to recurrent ulceration was 21 years (range, 10-36 years). All patients had undergone vagotomy and antrectomy (17 patients) or subtotal gastrectomy (3 patients). Presenting symptoms included gastric outlet obstruction (70%) and bezoar formation (60%). Endoscopic findings in this group of patients included a stenotic gastric outlet (70%) and marginal ulcerations (80%). Thirteen of 15 patients tested (87%) were Helicobacter pylori positive. Reoperation included partial resection of the gastric pouch and exploration for persistent vagus nerve. Twelve patients underwent Roux-en-Y reconstruction, whereas eight patients had Bilroth II reconstruction. Three of the latter group also had Braun enteroenterostomy performed. Good to excellent clinical results were obtained in 80 per cent of patients. The four patients with poor outcomes shared the following characteristics: 1) H. pylori-positive status, 2) presence of a preoperative bezoar, 3) Roux-en-Y reconstruction. Our current approach is to avoid Roux-en-Y construction in favor of Braun enteroenterostomy. Further prospective analysis of long-term postgastrectomy patients is needed to determine whether this clinical picture represents a new postgastrectomy syndrome.

D2 dopamine receptor gene (DRD2) Taq1 A polymorphism: reduced dopamine D2 receptor binding in the human striatum associated with the A1 allele

The relationship between a dopamine D2 receptor genetic polymorphism at the Taq1 A locus and the level of D2 receptor binding was investigated in normal, middle aged to elderly subjects with no psychiatric or neurological disorders. D2 receptor binding was measured by autoradiography in the caudate, putamen and nucleus accumbens, using the specific D2 receptor ligand [3H]-raclopride. In a sample of 44 individuals, only one was homozygous for the A1 allele, 25 were homozygous for A2 and 18 were heterozygotes. The presence of one or two A1 alleles was associated with reduced D2 receptor binding in all areas of the striatum, reaching statistical significance in the ventral caudate and putamen (p = 0.01 and p = 0.044, respectively). This reduction was more marked in males than females, particularly in the putamen. A genetic predisposition to lower D2 receptor expression may increase susceptibility to neuroleptic medication or clinical symptoms that are associated with diseases involving dopaminergic pathology.

Developmentally regulated expression of pfs16, a marker for sexual differentiation of the human malaria parasite Plasmodium falciparum

Sexual differentiation is essential for the transmission of Plasmodium to mosquitoes and therefore, for the spread of malaria. The molecular mechanisms underlying sexual differentiation are poorly understood but may be elucidated by a detailed study of the regulation of expression of sexual stage specific genes. In the present work we describe the differential expression of the gene encoding the sexual stage specific protein, Pfs16. We have conducted a comparative analysis of pfs16 promoter activity, RNA levels and the rate of de novo protein synthesis during development of Plasmodium falciparum. Furthermore, we have determined the pattern of expression of pfs16 transcripts at the single cell level by in situ hybridisation. We show that the expression of pfs16 is induced immediately following the invasion of a red blood cell in sexually committed ring stage parasites and continues throughout gametocytogenesis and in macrogametes. The expression of pfs16 is regulated at the level of transcription initiation and modulated by a post-transcriptional process. These results demonstrate that the expression of the pfs16 gene is the earliest event in the sexual differentiation process of P. falciparum described to date.

Radiation-induced chromatid breaks and DNA repair in blood lymphocytes of patients with dysplastic nevi and/or cutaneous melanoma

Each chromatid contains a single continuous molecule of double-stranded DNA, so chromatid breaks represent unrepaired DNA double-strand breaks. Frequencies of chromatid breaks after G2 phase x-irradiation were determined in phytohemagglutinin-stimulated blood lymphocytes from normal subjects and from four categories of patients with dysplastic nevi with or without cutaneous melanoma or with melanoma alone. Some cells were treated with an inhibitor of DNA repair replication to determine enzymatic incision activity at damaged sites after exposure to x-rays, UVC, or fluorescent light. Whereas one of 16 normal controls had deficient DNA repair, all 17 patients from families with hereditary dysplastic nevi with or without melanoma (category I) had a deficiency in repair of radiation-induced DNA damage, manifested as an abnormally high frequency of chromatid breaks after x-irradiation or a reduced capacity to incise the damaged sites after UV exposure. Four of 11 patients with sporadic dysplastic nevi alone (category II) and eight of 12 with sporadic dysplastic nevi and melanoma (category III) showed deficient DNA repair after x-irradiation. One of two patients with sporadic melanoma and no dysplastic nevi (category IV) was also deficient in repair of x-ray-induced damage. Deficient DNA repair thus appears to be associated with hereditary dysplastic nevi with or without melanoma. It also characterizes some patients with sporadic dysplastic nevi or melanoma.

Memories for the Marchioness

We examined the accounts of 27 survivors of the Marchioness ferry sinking, using cross-validation of accounts to search for instances of motivated forgetting. In order to identify objective items that could be validated, we focused the analysis on subjects' statements of whom they were with at various stages of the disaster. We compared these findings with an informal recall of a non-traumatic event after an interval of a few days. The main finding was that recall was reasonably good for both traumatic and non-traumatic events. Specifically, in the Marchioness sample, among those 86 statements that could have been confirmed in the accounts of other informants, 74 were in fact confirmed. Of the remaining 12 unconfirmed statements, only one involved a contradiction. We conclude that for a disaster of this kind, and with this particular sample of individuals, motivated forgetting was extremely rare.

Highly specific monoclonal antibody demonstrates that pregnancy-specific glycoprotein (PSG) is limited to syncytiotrophoblast in human early and term placenta

Pregnancy specific glycoproteins (PSG) in humans constitute a family of 11 closely related glycoproteins (PSG1-8, PSG11-13) of unknown function(s), which are produced in large amounts by the placenta. As a step toward understanding the biology of PSG, specific monoclonal antibodies (mAbs) against PSG were developed and used to investigate the ultrastructural localization of PSG in the early and term placenta and in first trimester decidua. One mAb, BAP-3, was found to react with all six individually expressed PSGs representing five alternatively spliced forms, but not with any of the seven expressed members of the carcinoembryonic antigen (CEA) subfamily. The BAP-3 epitope is located in the PSG B2 domain. Using the BAP-3 mAb, PSGs were found to be expressed exclusively by the syncytiotrophoblast of first trimester and term villi. The intensity of the staining was much higher in early than in term placenta. All three main cellular compartments involved in the biosynthesis pathway of secreted proteins, i.e. rough endoplasmic reticulum, the Golgi complex and secretory vesicles, were stained for PSG. A second PSG-reactive mAb, BAP-1, also stained the apical plasma membrane of some glandular epithelial cells in first trimester decidua in addition to syncytiotrophoblast. This staining was most likely due to cross-reactivity with biliary glycoprotein (BGP).

Inhaled nitric oxide in the management of cardiopulmonary disorders in infants and children

The administration of NO has become an important and effective therapy in the clinical management of pulmonary hypertension associated with cardiopulmonary disorders in infants and children. It is likely to become a routine therapy in the treatment of PPHN, although dosing and timing strategies, early indicators of treatment failure, and long-term outcomes are not completely understood. The use of NO has also been beneficial in the evaluation and management of pulmonary hypertension associated with congenital heart disease. The role of NO in the management of pediatric ARDS holds promise, although further clinical trials are needed. Additional research should also be directed toward the use of NO in preterm infants and those born with CDH. Future endeavors may also include the use of NO in the evaluation and management of asthma.

Genetic construction and characterization of an anti-monkey CD3 single-chain immunotoxin with a truncated diphtheria toxin

We have previously developed a chemically conjugated anti-rhesus monkey CD3 immunotoxin FN18-CRM9 that can deplete in vivo T cells and induce long term tolerance of mismatched renal allograft in rhesus monkeys. This immunotoxin is a monkey analogue of anti-human CD3 immunotoxin UCHT1-CRM9. In this study, we cloned the light and heavy chain variable regions of anti-monkey CD3 monoclonal antibody FN18 and constructed a single-chain Fv (sFv) by linking variable light and variable heavy regions with a (Gly4Ser)3 linker. The single-chain immunotoxin DT390-FN18sFv was constructed by ligating the sFv to the carboxyl terminus of DT390, a truncated form of diphtheria toxin. The DT390-FN18sFv fusion protein was expressed in Escherichia coli and purified with Ni-RTA affinity and anion exchange columns. Similar to the chemically conjugated immunotoxin FN18-CRM9, DT390-FN18sFv can also specifically inhibit protein synthesis in primary monkey T cells in a dose-dependent manner. DT390-FN18sFv at 10(-7) mol/L or FN18-CRM9 at 10(-8) mol/L is sufficient to reduce protein synthesis of monkey primary T cells to less than 5% of the control. The 50% inhibition dosage (IC50) of FN18-CRM9 is 1 x 10(-10) mol/L, while the IC50 of DT390-FN18sFv is 1 x 10(-8) mol/ L, reflecting the lowered affinity of monovalent Fab' FN18 to its parental divalent antibody. The availability of functional FN18sFv will provide the basis for the construction of divalent anti-CD3 immunotoxins for preclinical studies on the induction of tolerance in organ transplantation and experimental autoimmune diseases.

The DSM-IV Outline for Cultural Formulation: a critical demonstration with American Indian children

OBJECTIVE

The publication of DSM-IV is notable for the improved coverage of cultural issues in the diagnosis of mental disorders. In particular, Appendix I of DSM-IV includes an "Outline for Cultural Formulation" (Outline) which assists the clinician in evaluating the impact of an individual's cultural context on diagnosis and treatment. However, the capacity of the Outline to facilitate the development of comprehensive cultural formulations for children and adolescents has not been established. In this article the use of the Outline with American Indian children is reviewed critically.

METHOD

Based on the Outline, cultural case formulations for four American Indian children were developed and their comprehensiveness was assessed.

RESULTS

Applied to the case material, the Outline provided a clear template for the development of cultural formulations. Nonetheless, several gaps in the material required by the Outline were identified, particularly in the areas concerning cultural identity and cultural elements of the therapeutic relationship.

CONCLUSIONS

Clinicians working with children should recognize the strengths as well as the limitations of the Outline and expand their cultural descriptions accordingly. Several additions to the text of the Outline that will facilitate the development of comprehensive cultural formulations specific to children and adolescents are proposed.

Functional consequences of the somatopause and its treatment

The decline in the function of the growth hormone-releasing hormone, growth hormone, insulin-like growth factor (GHRH-GH-IGF) axis has been termed the somatopause. Many of the catabolic sequelae seen in normal aging has been attributed to this decrease in circulating GH and IGF-I. In order to provide hormone replacement therapy for the somatopause, elderly subjects have been treated with GH, IGF-I, or both hormones together. Whereas numerous beneficial effects on body composition, strength, and quality of life have been reported in some studies, other studies have reported only marginal functional improvements. Moreover, it is clear that both hormones can cause significant morbidity.

Human tenascin-C: identification of a novel type III repeat in oral cancer and of novel splice variants in normal, malignant and reactive oral mucosae

Tenascin-C is a mosaic, linear glycoprotein that is up-regulated during many normal and pathological processes involving either cell migration or tissue morphogenesis, such as invasion of malignant cells and wound healing. Human tenascin-C contains 8 consecutive type III fibronectin (TNCfn) domains that are involved in alternative splicing and potentially generate a large number of isoforms that code for tenascin-C proteins with subtly different functions. Human tenascin-C splice variants were investigated by RT-PCR in a range of normal and pathological oral mucosal tissues. A novel, 9th human TNCfn domain involved in alternative splicing was identified. It shares 70% nucleic acid and 55% protein sequence homology with chicken TNCfn-ad2. As in avians, this novel repeat was located between TNCfn-B and TNCfn-ad1 and accordingly was designated human TNCfn-ad2. Human TNCfn-ad2 was detected in only 2 of 10 oral cancers. However, TNCfn-ad2 was absent from 40 normal, reactive, pre-malignant and other oral mucosal specimens investigated. Previous studies have described 8 splice variant transcripts for human tenascin-C. By systematic investigation we identified further novel splice variants for human tenascin-C. Furthermore, our results indicate that many potential splice variants probably do not exist in the tissues investigated. Thus, we have demonstrated that human tenascin-C transcripts generate a complex but selected repertoire of different alternative splice products.

Central nervous system monoamine neurotransmitter turnover in primary and obesity-related human hypertension

Recent experiments in laboratory animals have challenged the conventional view that the dominant effect of CNS noradrenergic neurons in cardiovascular control is sympathetic nervous inhibition and blood pressure reduction, describing instead sympathetic activation. We have tested whether such a stimulant effect on sympathetic outflow is also evident in human hypertension. CNS norepinephrine turnover was estimated from the combined overflow of norepinephrine, MHPG and DHPG into the internal jugular veins. Cerebral blood flow scans allowed differentiation between cortical and subcortical jugular venous drainage. In patients with pure autonomic failure, jugular overflow of norepinephrine and metabolites was not reduced, indicating brain neurons and not cerebrovascular sympathetics was the source. In healthy men, CNS norepinephrine turnover and muscle sympathetic nerve activity were directly related (p < 0.02). Administration of the ganglion blocker, trimethaphan, caused a compensatory five-fold increase in jugular overflow of MHPG. Conversely, intravenous clonidine reduced CNS norepinephrine turnover by approximately 50%, this possibly representing a mechanism of drug action. In cardiac failure patients, sympathetic nervous activation was associated with a trebling of CNS norepinephrine turnover (p < 0.01). In untreated patients with essential hypertension, the sympathetic activation present was associated with 250% higher CNS norepinephrine turnover (p < 0.01), but in subcortical brain regions only. A close and direct relation exists between brain norepinephrine turnover and human sympathetic nervous activity. CNS release of norepinephrine, presumably in the forebrain where noradrenergic neurons are sympathoexcitatory and pressor, mediates increased sympathetic nerve firing in patients with essential hypertension.

6-phospho-alpha-D-glucosidase from Fusobacterium mortiferum: cloning, expression, and assignment to family 4 of the glycosylhydrolases

The Fusobacterium mortiferum malH gene, encoding 6-phospho-alpha-glucosidase (maltose 6-phosphate hydrolase; EC 3.2.1.122), has been isolated, characterized, and expressed in Escherichia coli. The relative molecular weight of the polypeptide encoded by malH (441 residues; Mr of 49,718) was in agreement with the estimated value (approximately 49,000) obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the enzyme purified from F. mortiferum. The N-terminal sequence of the MalH protein obtained by Edman degradation corresponded to the first 32 amino acids deduced from the malH sequence. The enzyme produced by the strain carrying the cloned malH gene cleaved [U-14C]maltose 6-phosphate to glucose 6-phosphate (Glc6P) and glucose. The substrate analogs p-nitrophenyl-alpha-D-glucopyranoside 6-phosphate (pNP alphaGlc6P) and 4-methylumbelliferyl-alpha-D-glucopyranoside 6-phosphate (4MU alphaGlc6P) were hydrolyzed to yield Glc6P and the yellow p-nitrophenolate and fluorescent 4-methylumbelliferyl aglycons, respectively. The 6-phospho-alpha-glucosidase expressed in E. coli (like the enzyme purified from F. mortiferum) required Fe2+, Mn2+, Co2+, or Ni2+ for activity and was inhibited in air. Synthesis of maltose 6-phosphate hydrolase from the cloned malH gene in E. coli was modulated by addition of various sugars to the growth medium. Computer-based analyses of MalH and its homologs revealed that the phospho-alpha-glucosidase from F. mortiferum belongs to the seven-member family 4 of the glycosylhydrolase superfamily. The cloned 2.2-kb Sau3AI DNA fragment from F. mortiferum contained a second partial open reading frame of 83 residues (designated malB) that was located immediately upstream of malH. The high degree of sequence identity of MalB with IIB(Glc)-like proteins of the phosphoenol pyruvate dependent:sugar phosphotransferase system suggests participation of MalB in translocation of maltose and related alpha-glucosides in F. mortiferum.

Neurturin responsiveness requires a GPI-linked receptor and the Ret receptor tyrosine kinase

Neurturin (NTN) is a recently identified homologue of glial-cell-line-derived neurotrophic factor (GDNF). Both factors promote the survival of a variety of neurons, and GDNF is required for the development of the enteric nervous system and kidney. GDNF signals through a receptor complex consisting of the receptor tyrosine kinase Ret and a glycosyl-phosphatidylinositol (GPI)-linked receptor termed GDNFR-alpha. Here we report the cloning of a new GPI-linked receptor termed NTNR-alpha that is homologous with GDNFR-alpha and is widely expressed in the nervous system and other tissues. By using microinjection to introduce expression plasmids into neurons, we show that coexpression of NTNR-alpha with Ret confers a survival response to neurturin but not GDNF, and that coexpression of GDNFR-alpha with Ret confers a survival response to GDNF but not neurturin. Our findings indicate that GDNF and neurturin promote neuronal survival by signalling through similar multicomponent receptors that consist of a common receptor tyrosine kinase and a member of a GPI-linked family of receptors that determines ligand specificity.