Granulocytes: effector cells or immunomodulators in the immune response to helminth infection?

Granulocytes are effector cells in defence against helminth infections. We review the current evidence for the role of granulocytes in protective immunity against different helminth infections and note that for each parasite species the role of granulocytes as effector cells can vary. Emerging evidence also points to granulocytes as immunomodulatory cells able to produce many cytokines, chemokines and modulatory factors which can bias the immune response in a particular direction. Thus, the role of granulocytes in an immunomodulatory context is discussed including the most recent data that points to an important role for basophils under this guise.

Malaria-specific antibody responses and parasite persistence after infection of mice with Plasmodium chabaudi chabaudi.

While it is known that antibodies are critical for clearance of malaria infections, it is not clear whether adequate antibody responses are maintained and what effect chronic infection has on this response. Here we show that mice with low-grade chronic primary infections of Plasmodium chabaudi or infections very recently eliminated have reduced second infections when compared with the second infection of parasite-free mice. We also show that parasite-specific antibody responses induced by infection of mice with Plasmodium chabaudi contain both short- and long-lived components as well as memory B cells responsible for a faster antibody response during re-infection. Furthermore, parasite-specific antibodies to the C-terminal fragment of merozoite surface protein-1 (MSP-1) undergo avidity maturation. However, antibodies with both low and high avidity persist throughout infection and after re-infection, suggesting repeated rounds of activation and maturation of memory B cells. Neither the avidity profile of the antibody response, nor its maintenance is affected by persisting live parasites. Therefore, differences in parasitemia in re-infection cannot be explained solely by higher levels of antibody or greater affinity maturation of malaria-specific antibodies. These data suggest that there may be an antibody-independent component to the early control of secondary infections in mice that are chronically infected.

Community refinement of glaucoma referrals.

AIM: To describe a Manchester-based glaucoma referral refinement scheme designed to reduce the number of false-positive referrals to the hospital eye service. To report on the first years results of this scheme and its financial costs to the NHS. METHODS: Patients with suspected glaucoma, instead of being referred to their GP and then on to the hospital eye service, were referred to a group of specially trained community optometrists working to an agreed set of referral criteria. Those patients who did not meet the referral criteria were returned to the referring optometrist, while those who met the referral criteria were referred directly to Manchester Royal Eye Hospital. The patient's GP was informed in all cases. RESULTS: The number of suspect glaucoma cases referred to the Manchester Royal Eye Hospital was reduced by 40%. This figure is close to the percentage of false-positive referrals measured at Manchester Royal Eye Hospital prior to the onset of this study. The information accompanying referral has been improved and the scheme produces a small financial cost saving to the NHS of approximately 17 pounds sterling per patient. CONCLUSION: Community refinement of suspect glaucoma offers some important benefits over the current referral pathway.

Utilization and effectiveness of a weight-based heparin nomogram at a large academic medical center.

OBJECTIVE: To determine the utilization rate of a weight-based heparin nomogram and to assess the performance of the nomogram outside of experimental conditions. STUDY DESIGN: Prospective cohort analysis. PATIENTS AND METHODS: A total of 747 consecutive patients treated with intravenous heparin therapy for any indication on an internal medicine service were evaluated for the utilization rate of the weight-based nomogram, the time needed to exceed heparin's therapeutic threshold (activated partial thromboplastin time [aPTT] of > 1.5 times the control value), and the time needed to achieve heparin's therapeutic range (aPTT of 1.5 to 2.4 times the control value). Physicians were encouraged to use the weight-based nomogram by using conventional continuing medical education techniques and by configuring the computerized order entry system to give physicians an equally easy and voluntary choice between choosing the weight-based nomogram or ordering heparin in the traditional fashion. RESULTS: The study program had no effect in increasing the utilization rate of the nomogram; this rate remained the same as before the program was initiated (10%). Less time was needed both to exceed the therapeutic threshold and to achieve a therapeutic range with the weight-based nomogram compared with physician-guided dosing (P < .001 and P = .021, respectively). No difference was demonstrated between the weight-based and physician-guided groups in incidence of bleeding complications or in the proportion of patients with one or more supratherapeutic aPTTs. CONCLUSIONS: The weight-based nomogram led to superior intermediate outcomes compared with physician-guided dosing. However, despite efforts intended to modify physician behavior, the utilization rate remained so low that it was ineffective. Further research into the reasons why physicians chose not to use the weight-based nomogram and further research into methods to translate efficacious therapies into effective patient care are indicated.

A surplus of physicians? The view of internists at a single institution.

BACKGROUND: The sizable increase in the United States physician workforce over the last 25 years has led to a concern by health policy analysts that we are training too few generalist physicians, too many specialists and too many doctors altogether. Nearly all analysts' studies report that the United States currently has an adequate or more than adequate supply of physicians; however, few reports discuss practicing physicians' view of the issues. OBJECTIVE: To determine internists' opinion regarding the current and future physician supply and specialty mix. DESIGN: Analysis of results of a mailed questionnaire. SETTING: Nine hundred bed academic medical center in southern Connecticut. PARTICIPANTS: Three hundred seventy eight internal medicine attendings, fellows and residents. MEASURES: Seventeen questions that covered 4 domains: is there or will there be a surplus of general internists, internal medicine subspecialists or total physicians in Connecticut or the United States; which internal medicine subspecialties have a current surplus; what is the correct primary care/specialty care mix for our physician workforce; and what subspecialties are current internal medicine residents planning to pursue? RESULTS: A total of 378 of 686 (55%) mailed surveys were returned. The majority of physicians reported that there is currently no surplus of physicians (68%) or general internists (90%) in the Unites States, but that there is a surplus of internal medicine subspecialists (68%). The majority of the physicians who responded that there is no current surplus reported that there would not be a surplus in 10 years. Subspecialties most frequently indicated to have a surplus in the United States were cardiology (70%) and gastroenterology (57%). A majority of internal medicine residents (66%) indicated that they planned to pursue subspecialty fellowship; the fellowship most commonly indicated was cardiology (23%). CONCLUSIONS: In contrast to the opinion of most health policy analysts, the majority of internists associated with our institution do not believe that there is or will be a physician surplus in the United States. Reasons for a difference of opinion between practicing internists and health policy analysts are worthy of further study.

Factors influencing the career choices of physicians trained at Yale-New Haven Hospital from 1929 through 1994.

PURPOSE: To examine factors that influenced, positively or negatively, the specialty career choices of physicians trained at Yale-New Haven Hospital (YNHH) from 1929 to 1994. METHOD: The authors sent questionnaires to 4,888 physicians who had trained or were training in YNHH-sponsored residency programs. The physicians rated 36 factors posited to be influenced in career choice on a seven-point Likert scale from very negative to very positive. The authors compared the means of each factor's ratings by decade of medical school graduation. RESULTS: The most positively rated influences were similar in each decade from the 1920s to the 1990s. These influences shared characteristics of intellectual curiosity ("intellectual content of the specialty" and "challenging diagnostic problems"), altruism ("interest in helping people" and "opportunity to make differences in people's lives"), and personal identity ("consistent with personality" and "possess the required skill or ability"). Negative factors, such as "demands on time and effort," "stress in the field," and "malpractice costs," were also consistently rated throughout the decades. CONCLUSION: The reasons that physicians choose certain specialty careers have not changed significantly over the past 65 years despite all the changes that have occurred in medicine. Physicians continue to seek professional opportunities that are viewed as intellectually challenging and of benefit to others.

A web-based risk management and medical-legal curriculum for graduate medical education.

An educational Web site on the topic of risk management and medical-legal issues was designed. The site incorporates a 25-question multiple-choice quiz where resident responses were stored in a database for quantitative analysis. Residents who browsed the educational module scored significantly higher on the quiz (81%) than those who did not (62%). The authors conclude that the Web site and accompanying quiz database offer a practical solution for the uniform delivery of risk management in graduate medical education.

Beta-amyloid peptides initiate the complement cascade without producing a comparable effect on the terminal pathway in vitro.

Activation of the classical complement cascade by beta-amyloid peptides has been hypothesized to underlie the neurodegeneration observed in Alzheimer's diseased brains. In this study, various lots of synthetic beta-amyloid peptides, A beta(1-40), A beta(1-42), and A beta(25-35), were tested for their ability to activate both early complement cascade events and formation of the membrane attack complex through terminal pathway activation. Unlike recent reports which did not assess activation of complement terminal pathway, we found that concentrations of beta-amyloid which activated early cascade events, to an extent comparable to aggregated IgG, failed to elicit formation of comparable levels of membrane attack complex.

The presence of the complement cascade does not lead to neuronal cell death in primary hippocampal cultures.

To investigate the consequences of complement activation on neuronal viability, the effects of serum treatment on neuron-rich and mixed neuronal/glial cultures were evaluated. The neurotoxicity observed following treatment with either human or rat serum was variable and did not appear to be mediated through a complement-mediated mechanism. Serum lots lacking CH50 activity induced neurotoxicity, and heat treatment of toxic lots of either human or rat sera did not abolish toxicity. In cases where serum treatment did not induce cell death, treatment with PIPLC to remove endogenous membrane-bound complement inhibitors prior to serum exposure, did not result in cell death.

Regulation of the release of interleukin-6 from human astrocytoma cells.

Recent evidence suggests that the level of interleukin-6 (IL-6) is elevated in Alzheimer's disease (AD) brains. IL-6 is produced by reactive glial cells and could potentially affect neuronal survival. Understanding the biochemical mechanism that regulates the production and release of IL-6 by astrocytic cells may help to identify potential targets for therapeutic intervention in AD. In the present study, glial fibrillary acidic protein-positive human U373MG astrocytoma cells were used as a model of reactive astrocytes. Production of IL-6 in response to drug treatment was monitored with an ELISA assay. Histamine (1-100 microM), substance P (SP; 1-100 nM), and human interleukin-1 beta (IL-1 beta; 1-30 pM) stimulated the release of IL-6 in a time- and concentration-dependent manner, with EC50 values of 4.5 microM, 8 nM, and 4.5 pM, respectively. The respective effects of histamine, SP, and IL-1 beta were effectively blocked by the histamine H1, SP, and IL-1 receptor antagonists, supporting a receptor-mediated event for these agents. Both histamine and SP enhanced the formation of inositol phosphates and increase intracellular calcium levels, suggesting that the phosphatidylinositol bisphosphate/protein kinase C pathway may be involved in the IL-6 release process. Indeed, phorbol 12-myristate 13-acetate, a protein kinase C activator, also evoked IL-6 release from the U373MG cells. On the other hand, IL-1 beta, which produces a much more robust release of IL-6 than histamine or SP, has no effect on inositol phosphate formation or intracellular calcium levels.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP is not involved in interleukin-1-induced interleukin-6 release from human astrocytoma cells.

We have previously shown that activation of the phosphatidyl-inositol/phospholipase C pathway could induce interleukin 6 (IL-6) release from U373MG human astrocytomes cells. We also found that, although interleukin 1 beta (IL-1 beta) did not activate phosphatidy-linositol turnover, it induced, a robust release of IL-6. In the present study, we examined the role of adenylate cyclase/cyclic 3',5'-adenosine monophosphate (cAMP) pathway in IL-6 release. Agents which mimicked (dibutyryl cAMP) or stimulated (isoproterenol and forskolin) cAMP formation were found to induce IL-6 release and their effects could be potentiated by 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor. On the other hand, in spite of its robust action on IL-6 release, IL-1 beta did not stimulate cAMP formation. Other possible signal transduction mechanisms involved in IL-1 beta-induced IL-6 release are discussed.

(S)-3-methyl-5-(1-methyl-2-pyrrolidinyl) isoxazole (ABT 418): a novel cholinergic ligand with cognition-enhancing and anxiolytic activities: I. In vitro characterization.

A diversity of nicotinic acetylcholine receptor (nAChR) subtypes has been identified in mammalian brain using recombinant DNA technology. Alterations in the activity of these acetylcholinegated ion channels have been implicated in a number of central nervous system disorders including Alzheimer's disease (AD). The potential therapeutic usefulness of (-)-nicotine [(S)-3-(1-methyl-2-pyrrolidinyl) pyridine], the prototypic agonist at nAChRs, is severely limited by side effects that are the result of activation of both cholinergic and noncholinergic pathways in the central and peripheral nervous systems. This study sought to determine the in vitro selectivity of (S)-3-methyl-5-(1methyl-2-pyrrolidinyl)isoxazole (ABT 418), a novel analog of (-)-nicotine in which the pyridine ring was replaced with an isoxazole bioisotere, to activate nAChRs. ABT 418 was a potent inhibitor of [3H]-cytisine binding to nAChR in rat brain (Ki = 3 nM) but was inactive (Ki > 10,000 nM) in 37 other receptor/neurotransmitter-uptake/enzyme/transduction system binding assays, including those for alpha-bungarotoxin, muscarinic and 5-hydroxytryptamine3 receptors. In PC12 cells, patch-clamp studies indicated that ABT 418 was an agonist with an EC50 value of 209 microM, a potency to activate cholinergic channel currents some 4-fold less than that of (-)-nicotine (52 microM). Channel current responses elicited by ABT 418 were prevented by the cholinergic channel blocker, mecamylamine. ABT 418 was also approximately 10-fold less potent (EC50 value = 380 nM) than (-)-nicotine (40 nM) in increasing [3H]-dopamine release from rat striatal slices, an effect that was blocked by the nAChR antagonist, dihydro-beta-erythroidine (10 microM).2+ In contrast, ABT 418 appeared equipotent with (-)-nicotine in enhancing 86Rb+ flux from mouse thalamic synaptosomes. ABT 418 demonstrated an in vitro pharmacological profile of cholinergic channel activation that was robust at some nAChR, but not others. The reasons for this are unclear. However, a nAChR subtype selectivity may account for the in vitro potency differences of ABT 418 on various neurotransmitter systems, and the substantial separation between the cognitive enhancement/anxiolytic benefits, and the reduced central nervous system side-effect liabilities seen in vivo. ABT 418 represents the first neuronal nAChR ligand that differentiates the toxicities/liabilities and other negative aspects normally associated with liabilities and other negative aspects normally associated with (-)-nicotine from the potential pharmacological benefits of selective cholinergic channel activation.

The academic physician-investigator: a crisis not to be ignored.

The academic physician-investigator faces many challenges. Obtaining funding to support research is the greatest impediment. The National Institutes of Health, the single largest source of grants for the academic physician-investigator, approved only 14.2% of new investigator grant applications in 1990, compared with 40% in 1965 and 1975. Physicians submitted 25% of all applications, and they have priority scores similar to those applications submitted by investigators with PhD degrees. The 14.2% funding rate for new investigator-initiated grants is considerably less than the 56% success rate of amended renewal investigator-initiated grants. These trends in funding can be discouraging to the new physician-investigator. In addition, more emphasis is placed on clinical practice to generate money to support the new academic physician. These two facts, reduced probability of obtaining a grant and the perceived need to see more patients for salary support, may jeopardize retention of young faculty members. Moreover, training to prepare physicians for academic careers has been poor, with no attention given to the projected needs of the academic centers or the nation. This article describes the dilemma facing young physician-investigators and provides recommendations for improvement to the leaders of American medicine.

Needle exchange decreases the prevalence of HIV-1 proviral DNA in returned syringes in New Haven, Connecticut.

PURPOSE: To report on the deployment of the syringe tracking and testing system in the New Haven needle exchange program, which is the first federally funded evaluation of a needle exchange program conducted in the United States. PATIENTS AND METHODS: A legal needle exchange for intravenous drug users began in New Haven, Connecticut, in November 1990. All syringes distributed by the program received unique tracking codes. Syringes were tracked and HIV-1 proviral DNA prevalence in returned syringes was assessed using polymerase chain reaction and Southern blotting. RESULTS: At the outset of the program, the prevalence of HIV-1 proviral DNA in syringes exceeded two thirds. Prevalence decreased rapidly to less than 45% during the first 3 months of the program and remained at this level for the following 10 months. During the periods of decreasing prevalence and subsequent steady state, no changes in the demographics of program participants or in the drug use habits of newly enrolling clients that could account for the decrease in HIV-1 prevalence in needles were detected. In addition, the program referred almost 20% of its clients to drug treatment programs. CONCLUSION: The needle exchange program in New Haven has decreased the percentage of syringes testing positive for HIV-1 proviral DNA among needle exchange clients while simultaneously serving as an entry point for drug treatment.

Synthesis and in vitro characterization of novel amino terminally modified oxotremorine derivatives for brain muscarinic receptors.

A series of novel 2-substituted acetylenic pyrrolidines and piperidines related to oxotremorine (1) were prepared and evaluated in vitro as muscarinic cholinergic agents at brain M1 and M2 receptors. One analogue, 3-(2-oxo-1-pyrrolidinyl)-1-[2(R)-pyrrolidinyl]-1-propyne hydrogen oxalate (6a), was found to be a partial agonist producing a PI hydrolysis response at cortical M1 receptors approximately 3-fold larger than that produced by 1. The intrinsic activity profile of 6a at brain muscarinic receptors is similar to those of azetidine oxo analogue 2 and dimethylamino oxo analogue. All three compounds are partial M1 agonists and full M2 agonists; however, the profile of 6a in binding studies is significantly different. While 2 and 3 exhibit large M2 selectivities ranging between 8-fold to several hundred-fold, the binding profile of 6a shows almost no subtype selectivity.

Dissociation between muscarinic receptor-mediated inhibition of adenylate cyclase and autoreceptor inhibition of [3H] acetylcholine release in rat hippocampus.

Activation of muscarinic cholinergic receptors (mAChRs) in the central nervous system reduces the catalytic activity of membrane-bound adenylate cyclase and attenuates depolarization-dependent release of acetylcholine (ACh). Inasmuch as reports have indicated that these mAChR-mediated responses exhibit pharmacological profiles similar to the M2 subclass of mAChR, the present studies were undertaken to ascertain whether attenuation of presynaptic adenylate cyclase activity [and concurrent reduction of intraneuronal cyclic AMP (cAMP) levels] underlies mAChR-mediated autoinhibition of electrically evoked ACh release. In [3H]choline-prelabeled rat hippocampal slices, the mAChR agonists oxotremorine (EC50 = 15 microM) and carbachol (EC50 = 80 microM) caused atropine-reversible inhibition of [3H]ACh release up to a maximum of 80% reduction. The rank order of potency for antagonist reversal of this inhibitory action (N-methylatropine = atropine greater than scopolamine much greater than pirenzepine) was generally consistent with an M2 mAChR-mediated response although pirenzepine was ineffective up to 1 mM. Under these assay conditions, forskolin (1-10 microM) and 8-bromo-cAMP (30-300 microM) enhanced electrically evoked [3H]ACh release maximally by 50 to 60%; however, neither agent significantly reversed mAChR agonist-induced inhibition of [3H]ACh release. Additional studies were undertaken to determine the consequences of chemically uncoupling mAChR from their G protein-adenylate cyclase effector system in this tissue. Whereas brief pretreatment with the sulfhydryl alkylating agent N-ethylmaleimide (30 microM) or pertussis toxin (1 microgram/ml) markedly attenuated carbachol inhibition of adenylate cyclase activity in hippocampal tissue, there was no concurrent reduction of carbachol-inhibited [3H] ACh release.(ABSTRACT TRUNCATED AT 250 WORDS)