Myeloid DAP12-associating lectin (MDL)-1 is a cell surface receptor involved in the activation of myeloid cells

Crosslinking of immunoreceptor tyrosine-based activation motif (ITAM)-containing receptor complexes on a variety of cells leads to their activation through the sequential triggering of protein tyrosine kinases. Recently, DAP12 has been identified as an ITAM-bearing signaling molecule that is noncovalently associated with activating isoforms of MHC class I receptors on natural killer cells. In addition to natural killer cells, DAP12 is expressed in peripheral blood monocytes, macrophages, and dendritic cells, suggesting association with other receptors present in these cell types. In the present study, we report the molecular cloning of the myeloid DAP12-associating lectin-1 (MDL-1), a DAP12-associating membrane receptor expressed exclusively in monocytes and macrophages. MDL-1 is a type II transmembrane protein belonging to the C type lectin superfamily and contains a charged residue in the transmembrane region that enables it to pair with DAP12. Crosslinking of MDL-1/DAP12 complexes in J774 mouse macrophage cells resulted in calcium mobilization. These findings suggest that signaling via MDL-1/DAP12 complexes may constitute a significant activation pathway in myeloid cells.

Genomic structure, tissue expression and chromosomal location of the LIM-only gene, SLIM1

Human SLIM1 is a recently described gene of the LIM-only class encoding four and a half tandemly repeated LIM domains. LIM domains are double zinc finger structures which provide an interface for protein/protein interactions and are conserved in a variety of nuclear and cytoplasmic factors important in cell fate determination and cellular regulation. Here we report the structural organization, expression pattern and chromosomal localization of the human SLIM1 gene. SLIM1 was found to contain at least five exons with all four introns disrupting the coding region at a similar position relative to the respective complete LIM domains. Northern blot analysis confirmed strikingly high expression of SLIM1 in skeletal muscle and heart, with much lower expression observed in several other tissues including colon, small intestine and prostate. The SLIM1 gene was assigned to human chromosome Xq26 using fluorescence in situ hybridization.

Studies towards the identification of potent, selective and bioavailable thrombin inhibitors

The application of selection criteria, based on potency and physicochemical parameters, to a candidate library of thrombin inhibitors is described. The utility of the approach is exemplified by the discovery of a potent, selective and bioavailable thrombin inhibitor 62.

Activation of an iron uptake mechanism from transferrin in hepatocytes by small-molecular-weight iron complexes: implications for the pathogenesis of iron-overload disease

The liver is one of the principal sites of iron overload in diseases such as hemochromatosis and beta thalassemia. Hence, much effort has been invested in examining the mechanisms of Fe uptake by hepatocytes. In the present study we have examined the effect of small molecular weight (M(r)) Fe complexes on Fe uptake from iron 59-labeled transferrin (Tf) and 59Fe-labeled citrate by primary cultures of hepatocytes. This was important to assess because Fe-citrate and saturated diferric Tf coexist in the serum of patients with untreated Fe overload. Preincubation of hepatocytes with the low-M(r) Fe complex ferric ammonium citrate (FAC; 25 microg/mL; (Fe) = 4.4 microg/mL) followed by incubation with 59Fe-Tf or 59Fe-citrate ((Fe) = 0.25 to 25 micromol/L) resulted in the marked stimulation of 59Fe uptake. For example, at a physiologically relevant Tf-Fe concentration of 25 micromol/L, there was an 8-fold increase in 59Fe uptake by cells incubated with FAC compared to control cells. In contrast, at Tf-Fe concentrations of 0.25 to 2.5 micromol/L, 59Fe uptake in FAC-treated cells was only 1-fold to 3-fold greater than that in the corresponding controls. These data suggest that the FAC-activated Fe uptake process predominates at physiologically relevant Tf concentrations above the saturation of the Tf receptor (TfR). This is the first study to demonstrate that preincubation of hepatocytes with Iow-M(r)Fe complexes can markedly increase Fe uptake from diferric Tf. In conclusion, these results may help to explain the loading of hepatocytes with Fe that occurs in Fe-overload disease despite marked down-regulation of the TfR.

A natural variant of the cysteine protease virulence factor of group A Streptococcus with an arginine-glycine-aspartic acid (RGD) motif preferentially binds human integrins alphavbeta3 and alphaIIbbeta3

The human pathogenic bacterium group A Streptococcus produces an extracellular cysteine protease [streptococcal pyrogenic exotoxin B (SpeB)] that is a critical virulence factor for invasive disease episodes. Sequence analysis of the speB gene from 200 group A Streptococcus isolates collected worldwide identified three main mature SpeB (mSpeB) variants. One of these variants (mSpeB2) contains an Arg-Gly-Asp (RGD) sequence, a tripeptide motif that is commonly recognized by integrin receptors. mSpeB2 is made by all isolates of the unusually virulent serotype M1 and several other geographically widespread clones that frequently cause invasive infections. Only the mSpeB2 variant bound to transfected cells expressing integrin alphavbeta3 (also known as the vitronectin receptor) or alphaIIbbeta3 (platelet glycoprotein IIb-IIIa), and binding was blocked by a mAb that recognizes the streptococcal protease RGD motif region. In addition, mSpeB2 bound purified platelet integrin alphaIIbbeta3. Defined beta3 mutants that are altered for fibrinogen binding were defective for SpeB binding. Synthetic peptides with the mSpeB2 RGD motif, but not the RSD sequence present in other mSpeB variants, blocked binding of mSpeB2 to transfected cells expressing alphavbeta3 and caused detachment of cultured human umbilical vein endothelial cells. The results (i) identify a Gram-positive virulence factor that directly binds integrins, (ii) identify naturally occurring variants of a documented Gram-positive virulence factor with biomedically relevant differences in their interactions with host cells, and (iii) add to the theme that subtle natural variation in microbial virulence factor structure alters the character of host-pathogen interactions.

Fibroblast growth factor homologous factor 2 (FHF2): gene structure, expression and mapping to the Börjeson-Forssman-Lehmann syndrome region in Xq26 delineated by a duplication breakpoint in a BFLS-like patient

Börjeson-Forssman-Lehmann syndrome (BFLS) is a syndromal X-linked mental retardation, which maps by linkage to the q26 region of the human X chromosome. We have identified a male patient with BFLS-like features and a duplication, 46,Y,dup(X)(q26q28), inherited from his phenotypically normal mother. Fluorescence in situ hybridisation using yeast artificial chromosome clones from Xq26 localised the duplication breakpoint to an approximately 400-kb interval in the Xq26.3 region between DXS155 and DXS294/DXS730. Database searches and analysis of available genomic DNA sequence from the region revealed the presence of the fibroblast growth factor homologous factor gene, FHF2, within the duplication breakpoint interval. The gene structure of FHF2 was determined and two new exons were identified, including a new 5' end exon, 1B. FHF2 is a large gene extending over approximately 200 kb in Xq26.3 and is composed of at least seven exons. It shows tissue-specific alternative splicing and alternative transcription starts. Northern blot hybridisation showed highest expression in brain and skeletal muscle. The FHF2 gene localisation and tissue-specific expression pattern suggest it to be a candidate gene for familial cases of the BFLS syndrome and other syndromal and non-specific forms of X-linked mental retardation mapping to the region.

Structural organization and chromosomal localization of three human galanin receptor genes

Human galanin receptor subtypes GALR1, GALR2, and GALR3 are encoded by separate genes that are located on human chromosomes 18q23, 17q25.3, and 22q13.1, respectively. The exon:intron organization of the gene encoding GALR2 (GALNR2) and GALR3 (GALNR3) is conserved, with exon 1 encoding the NH2-terminus to the end of transmembrane domain 3 and exon 2 encoding the remainder of the receptor, from the second intracellular loop to the COOH-terminus. This conservation of structural organization is indicative of a common evolutionary origin for GALNR2 and GALNR3. The exon:intron organization of the gene encoding GALR1 (GALNR1) is different from that of GALNR2 and GALNR3, with exon 1 encoding the NH2-terminus to the end of transmembrane domain 5, exon 2 encoding the third intracellular loop, and exon 3 encoding the remainder of the receptor, from transmembrane domain 6 to the COOH-terminus. The structural organization of GALNR1 suggests convergent evolution for this gene and represents a structural organization that is unique among genes encoding G-protein-coupled receptors.

The discovery of orally available thrombin inhibitors: studies towards the optimisation of CGH1668

The chemical optimisation of CGH1668 1 is described employing an in vivo model of absorption to determine the influence on bioavailability of single point modifications to five key molecular templates. The discovery of an orally bioavailable and selective thrombin inhibitor, 24, highlights the utility of this approach.

Fourth module of Xenopus interphotoreceptor retinoid-binding protein: activity in retinoid transfer between the retinal pigment epithelium and rod photoreceptors

PURPOSE

Interphotoreceptor retinoid-binding protein (IRBP), an extracellular protein believed to support the exchange of retinoids between the neural retina and retinal pigment epithelium (RPE) in the vertebrate eye, exhibits a modular, i.e., repeat, structure. The present study was undertaken to determine whether an individual module of IRBP has activity in retinoid transfer between the RPE and rod photoreceptors.

METHODS

The retinoid transfer activity of a recombinant protein corresponding to the fourth module of Xenopus laevis IRBP (X4IRBP) was examined in two ways. First, X4IRBP was tested for its ability to support the regeneration of porphyropsin in detached/reattached Xenopus retina/RPE-eyecups. Following illumination and removal of native IRBP, Xenopus eyecups supplemented with 42 microM X4IRBP or (as a control) Ringer's solution were incubated in darkness and then analyzed for regenerated porphyropsin. Second, toad (Bufo marinus) RPE-eyecup preparations were used to evaluate X4IRBP's ability to promote the release of 11-cis retinal from the RPE.

RESULTS

The regeneration of porphyropsin in X4IRBP-supplemented Xenopus retina/RPE-eyecups (0.45 +/- 0.04 nmol; mean +/- SEM, n = 11) exceeded that in controls (0.13 +/- 0.02 nmol, n = 11). For promoting the release of 11-cis retinal from the toad RPE, 42 microM X4IRBP was more effective than equimolar bovine serum albumin although considerably less than that of 26 microM native bovine IRBP.

CONCLUSIONS

The results indicate a low but significant activity of IRBP's fourth module in reactions relevant to retinoid exchange.

Fragile sites still breaking

Rare fragile sites on chromosomes are the archetypal dynamic mutations. They involve large expansions of the microsatellite CCG or AT-rich minisatellites. The mutation process is an increase in repeat-unit number from within a normal range, through a premutation range, up to full mutation where the fragile site is expressed. Full mutations can inactivate genes and are regions of genomic instability. Common fragile sites, in particular, might have a role in oncogensis by facilitating gene inactivation through chromosomal deletion or amplification, but this requires further exploration. The mechanisms behind the changes that give rise to the cytogenetic manifestation of chromosomal fragility are now beginning to be understood.

Medical investigations and resulting countermeasures in support of 16-day Space Shuttle missions

Investigations with crew subject participants were flown on over 40 Shuttle missions (STS-32 through STS-73). All Astronauts who flew volunteered to participate in one or more of these studies, resulting in approximately 700 individual performances or data points for the 45 Detailed Supplementary Objectives (DSOs).

Physical activity and minority women: a qualitative study

Few physical activity research studies have been conducted with minority women. The purpose of this study was to explore patterns of physical activity among minority women. Focus groups were conducted with volunteers older than age 40. Each group was led by a trained moderator familiar with the ethnic community targeted. The sessions were audiotaped and professionally transcribed. Constructs were researched and codes were developed. Data were analyzed using NUD*IST qualitative analysis program. While participants did not identify themselves as "exercisers," they indicated they got enough physical activity from caregiving, housekeeping, and workday activities. The most common environmental barriers to becoming more physically active included safety, availability, and cost. Personal barriers included lack of time, health concerns, and lack of motivation. Results indicate the importance of terminology and assessment when conducting physical activity research in these populations. Also, results suggest many barriers are changeable with policies and interventions.

Characterisation of citrate and iron citrate uptake by cultured rat hepatocytes

BACKGROUND/AIMS

The endogenous low molecular weight iron chelator, citrate, is considered to be an important contributor to iron transport and the liver the main site of uptake of iron citrate in subjects suffering from diseases of iron overload. Moreover, the citrate-metabolising enzyme, aconitase, is implicated in the regulation of cellular iron metabolism. This study was undertaken to determine the role of citrate and ferric citrate in the uptake of iron by rat hepatocytes.

METHODS

Cultured rat hepatocytes were incubated (37 degrees C, 15 min) with 100 microM [14C]-citrate in the presence or absence of 1.0 microM 55Fe. Membrane-bound and intracellular radiolabel were separated by incubation with the general protease, Pronase.

RESULTS

Our results suggest that ferric citrate uptake is mediated by a specific citrate binding site which exhibits a higher affinity for citrate in the presence of iron than in its absence. Citrate was internalised by hepatocytes, with at least 70% being oxidised to CO2 within 15 min. Citrate uptake was pH-dependent, did not require the presence of sodium and increased with increasing iron concentration. Metabolic energy, anion channels, the Na+, K+-ATPase and vesicle acidification do not appear to play a role in uptake of ferric citrate, but functional sulphydryl groups may be involved.

CONCLUSIONS

The data suggest either that ferric citrate complexes with higher molar ratios of iron to citrate relative to the incubation medium are bound preferentially to the membrane, or that once citrate has delivered its iron to the membrane, the complex dissociates and the components are internalised separately.

Learners' experience of continuing medical education events: a qualitative study of GP principals in Dorset

BACKGROUND

General practitioners' (GPs') attendance at continuing medical education (CME) events has increased since the introduction of the Post Graduate Educational Allowance (PGEA) in 1990. However, few studies have examined doctors' perceptions about their continuing education, and explored their views in depth.

AIM

To investigate general practitioners' experience of CME events, what personal impact they had, and how the GPs perceived the influence of CME in their professional practice and patient care.

METHOD

A qualitative study, with in-depth semi-structured interviews, of a purposive sample of 25 general practitioners in Dorset was conducted. Content analysis was used to identify major themes from the transcripts.

RESULTS

GPs perceived CME events as beneficial. Confidence levels rose, and the events provided a break from practice that refreshed and relaxed, thus indirectly benefiting patients. The opportunities provided by formal events for informal learning and exchange of ideas, with both peers in general practice and consultant colleagues, were highly valued. The relevance of the subject to general practice, and the appropriateness of the educational format, were considered of paramount importance. Few responders identified major changes in their practice as a result of formal CME events, and information was seldom disseminated among practice colleagues.

CONCLUSION

The results of this study challenge GP educators to provide CME that is relevant, to recognize the value of peer contact, and to facilitate the incorporation of new information into practice.

Prenatal failure to visualize kidneys: a spectrum of disease

OBJECTIVES

To better understand the outcomes and management of patients when there is a failure to visualize kidneys on prenatal ultrasound.

METHODS

Nine thousand five hundred twelve prenatal ultrasound studies performed on 4900 patients were reviewed retrospectively for the findings of a failure to visualize kidneys. The prenatal ultrasounds, pregnancy outcomes, and postmortem studies were reviewed for each of the 10 patients identified.

RESULTS

Nine of 10 patients experienced fetal death in the index pregnancy: 7 had therapeutic abortions, 1 had an intrauterine fetal demise, and 1 gave birth to a stillborn infant. One patient gave birth to a live infant with Bartter's syndrome and grossly normal kidneys, as diagnosed by ultrasound. Developmental renal anomalies were identified in only 4 of 10 cases, and only 2 patients had true bilateral renal agenesis. There was 1 case each of bilateral renal medullary cystic dysplasia and bilateral renal hypoplasia. Three cases had no renal anomalies and included 1 case each of Turner's syndrome, chronic abruption, and a cord accident. In 2 cases, postmortem examinations were not performed because of family wishes.

CONCLUSIONS

Prenatal failure to visualize kidneys represents a spectrum of clinical problems not all of which are fatal. Close consultation with an experienced ultrasonographer is essential to provide informed counseling to expectant parents. Pathologic examination should be recommended when there is fetal demise and a suspicion of genitourinary anomalies. Screening of family members of the index patient and genetic counseling may be indicated.

Molecular characterization, pharmacological properties and chromosomal localization of the human GALR2 galanin receptor

The neuropeptide galanin mediates a diverse spectrum of biological activities by interacting with specific G protein-coupled receptors. We have used homology genomic library screening and polymerase chain reaction (PCR) techniques to isolate both genomic and cDNA clones encoding the human homolog of the recently cloned rat GALR2 galanin receptor. By fluorescence in situ hybridization, the gene encoding human GALR2 (GALNR2) has been localized to chromosome 17q25.3. The two coding exons of the human GALNR2 gene, interrupted by an intron positioned at the end of transmembrane domain III, encode a 387 amino acid G protein-coupled receptor with 87% overall amino acid identity with rat GALR2. In HEK-293 cells stably expressing human GALR2, binding of [125I]porcine galanin is saturable and can be displaced by galanin, amino-terminal galanin fragments and chimeric galanin peptides but not by carboxy-terminal galanin fragments. In HEK-293 cells, human GALR2 couples both to Galphaq/11 to stimulate phospholipase C and increase intracellular calcium levels and to Galphai/o to inhibit forskolin-stimulated intracellular cAMP accumulation. A wide tissue distribution is observed by reverse transcriptase (RT)-PCR analysis, with human GALR2 mRNA being detected in many areas of the human central nervous system as well as in peripheral tissues.

Abnormalities of nasal potential difference measurement in Liddle's syndrome

In Liddle's syndrome, a rare inherited form of hypertension, epithelial sodium channel mutations appear to cause high blood pressure by increasing sodium reabsorption through sodium channels in the renal distal tubule. This increase in channel activity has not been confirmed previously by in vivo measurement. We have made transnasal potential difference measurements (effective in detection of increased sodium channel activity in cystic fibrosis) in three brothers with genetically proven Liddle's syndrome, their unaffected sister, and 40 normotensive controls. Maximum potential difference after 2 wk off treatment in the affected brothers was -30.4+/-1.2 mV (values mean+/-SD, lumen-negative with respect to submucosa) and was significantly more lumen-negative than that of the control group (-18.6+/-6.8 mV, P = 0.0228) or the unaffected sister (-18.25 mV, P < 0.01). The change in potential difference after topical application of 10(-)4 M amiloride was greater in the Liddle's patients, 14.0+/-2.1 mV, than in controls (7.9+/-3.9 mV, P = 0.0126) or the unaffected sister (5.5 mV, P < 0.05). This is the first in vivo demonstration of increased sodium channel activity in Liddle's syndrome. If these results are confirmed in other kindreds with this condition, then nasal potential difference measurements could provide a simple clinical test for Liddle's syndrome.

Peritumoral CD1a-positive dendritic cells are associated with improved survival in patients with tongue carcinoma

OBJECTIVES

To determine if survival and recurrence rates for patients with squamous cell carcinoma of the tongue correlate with the degree of dendritic cell (DC) infiltration of the primary tumor or adjacent tongue tissue and if there is an association between tumor or nodal stage and DC infiltration.

DESIGN

Hospital and office medical records were reviewed to obtain 5-year follow-up data. Original pathology specimens were recut and stained for the cell surface markers S100 and CD 1a. The number of DCs present in the specimens was quantified microscopically and compared statistically with patient outcome and staging.

SETTING

A university hospital.

PATIENTS

All patients who underwent resection of primary squamous cell carcinoma of the tongue from January 1, 1987, through December 31, 1990, for whom 5-year follow-up data and original pathology specimens were available (N=43).

MAIN OUTCOME MEASURES

Time to recurrence, death, or both.

RESULTS

Patients who had greater numbers of CD1a-positive DCs adjacent to tumor had improved survival (P=.02) and decreased recurrence rates (P=.06). The other subpopulations of DCs examined were not associated with survival or recurrence. In addition, the number of CD 1a-positive DCs in peritumoral epithelium decreased as the tumor stage increased (P=.01) and if nodal metastases were present (P=.05).

CONCLUSIONS

Dendritic cells are antigen-presenting cells that are thought to play a major role in the antitumor immune response. The CD1a surface antigen has been shown to mediate T-cell interactions. The association between CD1a-positive peritumoral DCs and patient outcome suggests an important function for this cell population.

Construction of a high-resolution physical and transcription map of chromosome 16q24.3: a region of frequent loss of heterozygosity in sporadic breast cancer

A breast cancer tumor suppressor gene has been localized to chromosome 16q24.3 by loss of heterozygosity (LOH) studies of breast tumor DNA. To identify candidate genes for this suppressor function, we have constructed a detailed physical map extending approximately 940 kb from the telomere of the long arm of chromosome 16 that encompasses the minimum LOH interval. This contig consists of a minimum overlapping set of 35 cosmids and a single PAC clone that were aligned by restriction enzyme site mapping. Cosmids were initially identified by screening filters with markers localized to the region by physical mapping using mouse/human somatic cell hybrids, and subsequently cosmid ends were used to complete the contig. A total of seven known genes, including PRSM1, PISSLRE, and the recently cloned Fanconi anemia A (FAA) gene, and potential transcripts from exon-trapping experiments have been located to this contig. A minimum of 14 new transcripts have been identified based on homology of trapped exons with database sequences. This contig and expressed sequence map will form the basis for the identification of the breast cancer tumor suppressor gene in this region.

Public health response for the 1996 Olympic Games

Extensive planning and preparation by public health agencies were required for the provision of public health services during the 1996 Centennial Olympic Games, which brought together more than 10000 athletes from 197 countries and more than 2 million visitors. Public health activities included the development and use of an augmented surveillance system to monitor health conditions and detect disease outbreaks; creation and implementation of 6 environmental health regulations; establishment of a central Public Health Command Center and response teams to coordinate response to public health emergencies; planning for potential mass casualties and the provision of emergency medical services; implementation of strategies for the prevention of heat-related illness; and distribution of health promotion and disease prevention information. Public health agencies should take the lead in organizing and implementing a system for preventing and managing public health issues at future large-scale public events such as the Olympics.

Localization of human cadherin genes to chromosome regions exhibiting cancer-related loss of heterozygosity

This report presents the chromosomal localization of cadherin genes. Cadherins are cellular adhesion molecules. Since disturbance of intracellular adhesion is important for invasion and metastasis of tumor cells, cadherins are considered prime candidates for tumor suppressor genes. A variety of solid tumors show loss of heterozygosity of the long arm of chromosome 16, which is indicative of the potential location of tumor suppressor genes. Refined and new localizations of six cadherin genes (CDH3, 5, 8, 11, 13, and 15) to the long arm of chromosome 16 are shown. CDH15 was localized to 16q24.3, in a region that exhibits loss of heterozygosity in a number of sporadic breast cancer tumors. Previous localization of CDH13 (H-cadherin) to 16q24 suggested this gene as a tumor suppressor candidate in the 16q24.3 loss of heterozygosity region; however, refined mapping presented in this report localizes CDH13 proximal to this region. A human EST homologous to the chicken cadherin-7 was partially sequenced and found to represent a new human cadherin. This cadherin mapped to chromosome 18q22-q23, a region that exhibits loss of heterozygosity in head and neck squamous cell carcinomas. CDH16 was localized to 8q22.1, a region exhibiting loss of heterozygosity in adult acute myeloid leukemia.

FRA10B structure reveals common elements in repeat expansion and chromosomal fragile site genesis

A common mechanism for chromosomal fragile site genesis is not yet apparent. Folate-sensitive fragile sites are expanded p(CCG)n repeats that arise from longer normal alleles. Distamycin A or bromodeoxyuridine-inducible fragile site FRA16B is an expanded AT-rich approximately 33 bp repeat; however, the relationship between normal and fragile site alleles is not known. Here, we report that bromodeoxyuridine-inducible, distamycin A-insensitive fragile site FRA10B is composed of expanded approximately 42 bp repeats. Differences in repeat motif length or composition between different FRA10B families indicate multiple independent expansion events. Some FRA10B alleles comprise a mixture of different expanded repeat motifs. FRA10B fragile site and long normal alleles share flanking polymorphisms. Somatic and intergenerational FRA10B repeat instability analogous to that found in expanded trinucleotide repeats supports dynamic mutation as a common mechanism for repeat expansion.

Ferric citrate uptake by cultured rat hepatocytes is inhibited in the presence of transferrin

Diseases associated with iron overload occur worldwide. In subjects suffering from these conditions, transferrin is likely to be fully saturated and excess plasma iron must be complexed to other molecules. Consequently, the liver, which is the major site of iron storage, will be presented with iron in both transferrin-bound and non-transferrin-bound forms and these forms may compete for uptake by hepatocytes. The endogenous low-molecular-mass iron chelator, citrate, is considered to be a major contributing molecule to non-transferrin iron transport. This study was conducted to investigate the effects of transferrin on the uptake of citrate and iron citrate by hepatocytes in culture. Rat hepatocytes were incubated with 100 microM [14C]citrate and 1.0 microM 55Fe in the presence or absence of various forms of transferrin. Binding and internalisation of both citrate and iron were inhibited in a dose-dependent manner with increasing concentration of diferric transferrin, with iron uptake decreasing to less than 5% of control values. Apotransferrin was markedly more effective in blocking citrate and iron uptake, reaching the same levels of inhibition at a 15-fold lower concentration of protein. The binding of citrate to the cell membrane was not affected significantly by changing the iron saturation of transferrin but internalisation decreased with decreasing saturation. In contrast, both the binding and internalisation of iron decreased with decreasing saturation. Incubations carried out using 55Fe-labelled citrate in the presence of 59Fe-labelled diferric transferrin indicated that citrate-mediated iron binding by the cells decreased with increasing diferric transferrin concentrations but the citrate iron was not replaced by iron from transferrin during the 15-min incubation period. Instead, total iron uptake decreased. These data suggest that citrate-mediated iron uptake by hepatocytes shares at least one common pathway with transferrin-mediated iron uptake.

Characterisation of non-transferrin-bound iron (ferric citrate) uptake by rat hepatocytes in culture

Under conditions of iron overload plasma transferrin can be fully saturated and the plasma can transport non-transferrin-bound Fe which is rapidly cleared by the liver. Much of this Fe is complexed by citrate. The aim of the present work was to characterise the mechanisms by which Fe-citrate is taken up by hepatocytes using a rat hepatocyte cell culture model. The cells, after one day in culture, were incubated with 59Fe-labelled Fe-citrate for varying time periods, then washed and Fe uptake to the membrane and intracellular compartments of the cell was determined by radioactivity measurements. Maximal rates of internalisation of Fe occurred at a Fe:citrate molar ratio of 1:100 or greater, a pH of approximately 7.4 and an extracellular Ca2+ concentration of 1.0 mM. Fe uptake showed Michaelis-Menten kinetics and was a temperature-dependent process. The K(m) and Vmax for Fe internalisation by the cells at 37 degrees C were approximately 7 microM and 2 nmol/mg DNA/min (25 x 10(6) atoms/cell/min), respectively; and the Arrhenius activation energy was 35 kJ/mol. The transition metals, Zn2+, Co2+ and Ni2+, inhibited Fe uptake when used at 10 and 100 times the concentration of Fe. The rate of Fe internalisation from Fe-citrate was found to be approximately 20 times as great as that from Fe-transferrin with Fe concentrations of 1 and 2.5 microM for both forms of Fe. The rate of Fe uptake by iron-loaded hepatocytes obtained from rats which had been fed carbonyl Fe was not significantly different from that by normal hepatocytes. These experiments show that rat hepatocytes in primary culture have a high capacity to take up non-transferrin-bound Fe in the form of Fe-citrate and that uptake occurs by facilitated diffusion. The iron transport process does not appear to be regulated by cellular Fe levels.

Evaluation of a primary care counselling service in Dorset

BACKGROUND

Research into the effectiveness of counselling in primary care is rare. This study attempts to provide a thorough evaluation of the effects of a new counselling service introduced throughout Dorset.

AIM

To evaluate the impact of counselling on client symptomatology, self-esteem, and quality of life. The effect of counselling on drug prescribing, referrals to other mental health professionals, and client and general practitioner (GP) satisfaction were also assessed.

METHOD

All new clients referred for counselling were asked to complete and return questionnaires before and after counselling. A total of 385 clients took part in the study. The first and second assessments were compared statistically. Clients were ascribed a psychiatric diagnosis using a simplified version of DSM-IIIR (Diagnostic and Statistical Manual of the American Psychiatric Association). GPs' views of the service were determined using a specially designed questionnaire. Drug data were obtained from the Prescription Pricing Authority and referral statistics from Dorset HealthCare National Health Service (NHS) Trust.

RESULTS

The number of psychiatric symptoms and their severity were significantly reduced by counselling. There were no significant differences in the prescription of anxiolytic/hypnotic and anti-depressant medication between matched practices with and without counsellors. The presence of a counsellor did not affect the rate of referral to other mental health professionals. Clients and GPs valued the service highly.

CONCLUSIONS

The Psychology Managed Counselling Service is an effective method of running a counselling service and is well received by both clients and GPs. Counselled clients improved significantly on several measures.