Photoreceptor differentiation of isolated retinal precursor cells includes the capacity for photomechanical responses

Isolated retinal precursor cells, grown without pigment epithelial or glial cells and in the absence of intercellular contacts, develop a complex set of photoreceptor-specific properties, including polarized structural and molecular organization and opsin immunoreactivity. We report here that these isolated embryonic photoreceptors are also capable of responding to light. Sequential photography showed that 50% of the photoreceptors grown in a light cycle elongate when exposed to light and contract in response to darkness. A smaller population (20%) showed the opposite response. Responses of individual cells could be observed during several sequential light cycles and resemble photomechanical movements in vivo [Ali, M. A. (1971) Vision Res. 11, 1225-1288]. The differentiation program expressed by isolated precursor cells, therefore, includes the capacity for highly complex functional activities that require light sensitivity. These observations raise challenging questions regarding the nature of the chromophore and pigments that mediate light-regulated behaviors of cultured photoreceptors.

A finger-stick assay for determination of immunity to hepatitis A: a preliminary report

A simple and reproducible method for determining immunity to hepatitis A has been developed, using whole blood obtained by finger-stick and fixed on small discs. This method permits screening of large populations of candidates prior to active or passive immunization, avoiding the discomfort and difficulty of venipuncture, especially in children. The technique involves a finger-stick with a blood lancet, collection of 20 microliter whole blood on a paper disc which is then dried at room temperature. Perforated discs are incubated with phosphate buffered saline and the eluate is then tested for anti-HAV using the HAVAB assay. Results of anti-HAV assays from finger-stick samples obtained from adults and from children, showed 100% conformance with the homologous venous serum samples obtained at the same time. The lower threshold for detection of anti-HAV by this method is currently below 100 mIU/ml, as compared to 20 mIU/ml by the modified HAVAB method. In conclusion, we have developed a simple and reliable method for determination of immunity to HAV using whole blood obtained by finger-stick and fixed on paper discs. Samples can be collected under field trial conditions, without immediate need for laboratory facilities for separation and storage of serum samples. This sampling method, which is mainly intended for qualitative determination of anti-HAV in HAV immune subjects, especially under field trial conditions, is rapid, economical, efficient and acceptable to populations that are generally apprehensive of conventional venipuncture specimen collection methods.

Single and booster dose responses to an inactivated hepatitis A virus vaccine: comparison with immune serum globulin prophylaxis

Pre- and postexposure prophylaxis against hepatitis A virus (HAV) infection with immune serum globulin (Ig) is only effective for 4-6 months. We compared the safety, tolerability and immunogenicity of a single i.m. injection of Ig with a single and booster dose of an inactivated hepatitis A virus vaccine (iHAV) in adults. Healthy volunteers (18-50 years) received a single Ig i.m. injection (n = 30), or iHAV i.m. (n = 15) at 0 and 24 weeks, or placebo (n = 4) at the same intervals. Anti-HAV seroconversion was measured by radioimmunoassay (RIA) and neutralizing antibodies by an antigen reduction assay. After Ig injection (0.06 ml/kg), anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12 and 0% by week 20. In contrast, after a single 25 ng dose, RIA seropositivity in iHAV vaccinees was 80% by week 2, reaching 100% by week 5 and persisted up to week 24, at which time anti-HAV geometric mean titres (GMT) were two fold higher than those seen at week 1 after Ig. Postbooster anti-HAV titres in iHAV recipients rose within 4 weeks to 73-fold greater than the peak GMT seen one week after Ig, and 400-fold higher than GMT at 12 weeks after Ig. Neutralizing antibody titres after iHAV followed a similar pattern, as observed for anti-HAV. iHAV was well tolerated; placebo and vaccine tolerability were indistinguishable, with no serious adverse experiences observed. In conclusion, active vaccination with a single iHAV dose may eventually replace Ig for pre-exposure prophylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety, tolerability, and immunogenicity of an inactivated hepatitis A vaccine: effects of single and booster injections, and comparison to administration of immune globulin

Hepatitis A virus (HAV) infection in adults is often symptomatic and disabling. The present article summarizes our experience with phase 2 studies of an inactivated hepatitis A virus vaccine. Pre- and post-exposure prophylaxis with immune globulin (IG) is only effective for 4-6 months. We compared the safety, tolerability, and immunogenicity of a single i.m. injection of IG with single and booster doses of an inactivated hepatitis A virus vaccine (iHAV) in adults. A total of 75 healthy volunteers (aged 18-50 years) were evaluated in two separate studies. The first included 15 volunteers who received 25 units iHAV i.m. at 0 and 24 weeks. The second, a randomly controlled study, consisted of three groups receiving 25 units iHAV i.m. at 0, 1, and 6 months, or at 0, 2, and 6 months, or 0.06 ml/kg IG i.m. given once. Anti-HAV seroconversion was measured by radioimmunoassay (RIA). After IG injection, anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12, and 0% by week 20. In contrast, after a single 25-unit dose, RIA seropositivity in iHAV vaccines was 73% by week 2, reaching 100% by week 5, and persisted in all up to week 24, at which time anti-HAV geometric mean titers (GMT) were 2-fold higher than those seen at week 1 after IG. Administration of a booster dose given 1 or 2 months after primary immunization did not significantly improve the quantitative anti-HAV response at 6 months as compared to the effect of the primary dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental regulation of adenosine A1 receptors, uptake sites and endogenous adenosine in the chick retina

Although adenosine A1 receptors mediate the inhibition of dopamine-dependent stimulation of adenylate cyclase activity in the developing chick retina, their localization and function are unknown. We have examined the localization of these receptors, and of endogenous adenosine and adenosine uptake sites at several stages of chick retinal development. A1 receptors were already localized predominantly to plexiform regions by embryonic day 12 (E12) with no gross changes at subsequent stages. Adenosine immunoreactivity was absent from retina at E8 but was detected at E12 in the ganglion cell layer, as well as cells in the inner nuclear cell layer and photoreceptors. At more advanced developmental stages the immunoreactivity was greater, but displayed similar localizations. Uptake sites labeled with [3H]nitrobenzylthioinosine (NBI) were detected even earlier using binding and autoradiographic methods. [3H]NBI binding was saturable, and Scatchard analysis demonstrated a single class of sites with a Kd of 0.91 nM and Bmax of 298 fmol/mg protein in E15 retinal membranes. The binding was displaced by unlabeled NBI and dipyridamole. NBI binding sites differentiated earlier than adenosine A1 receptors or endogenous adenosine immunoreactivity, showing a diffuse distribution at E8, but predominating in the plexiform layers of more developed retinas. The results indicate that elements of a putative purinergic system differentiate at specific localizations early in retinal development.

Differentiation of retinal precursor cells born in vitro

It is not known whether the differentiated fate of retinal precursor cells is determined before, during, or after terminal mitosis. Previous studies from this laboratory led to the hypothesis that retinal precursor cells remain plastic after final mitosis and will follow a photoreceptor "default pathway" unless induced to develop as neurons by intraretinal factors. This hypothesis predicts that isolated precursors undergoing terminal mitosis and differentiation in cell culture, in the absence of the retinal microenvironment, should become photoreceptors, regardless of embryonic age. To test this prediction precursor cells were dissociated from 5- to 8-day chick embryo retinas and grown as single cells in vitro. Bromodeoxyuridine (BRDU)- and [3H]thymidine-labeling techniques, coupled with serial photography of precursor development in culture, showed that at all donor ages some of the isolated cells divided one or more times and became postmitotic in vitro. Analysis of cell phenotype by phase-contrast microscopy, sequential photography, autoradiography, and immunocytochemistry showed that the majority of precursors from all donor ages differentiated as photoreceptors. These observations support a prediction derived from the "photoreceptor default" hypothesis.

Estrogen suppresses hepatitis B virus expression in male athymic mice transplanted with HBV transfected Hep G-2 cells

Hormones are known to regulate both viral and cellular genes. It has been shown previously that estrogen has an effect on liver gene transcription and mRNA stability. Sex hormones might have a role in the chronic persistence of hepatitis B virus (HBV) infection. In fact, there is a male preponderance in the incidence of chronic HBV infection, and HBsAg expression was reported to be much higher in male transgenic mice than in the females. We investigated the effect of estrogen on HBV gene expression and regulation in athymic mice bearing 2.2.15 cells, a human hepatoblastoma cell line derived from Hep G-2 transfected with HBV sequences. Both male and female mice were treated with estradiol after tumors could be observed. Episomal DNA was extracted from the tumors and hybridized with 32P-labelled HBV DNA. Southern blot and slot blot analyses demonstrated that male mice had higher expression of HBV DNA. Estrogen treatment suppressed HBV DNA expression in males, but had only a minor effect on females. HBeAg production in male mice was also inhibited by estrogen treatment. HBV RNA extracted from 2.2.15 cells showed 2-3-fold reduction following beta-estradiol treatment. Moreover, inhibition of HBV transcription by estrogen was demonstrated by an RNA pulse-labelling experiment. These data indicate that estrogen inhibits HBV expression in the in vivo model presented in this study. These results might contribute to a better understanding of the effect of sex hormones on the pathogenesis of HBV-induced liver disease.

Accurate determination of the time of cell birth using a sequential labeling technique with [3H]-thymidine and bromodeoxyuridine ("window labeling")

During tissue embryogenesis, precursor cells divide actively and eventually withdraw from the mitotic cycle before differentiation. Accurate information about the time of terminal mitosis ("birthdate") of precursors is of vital importance for studying relationships between cell proliferation and differentiation. Methods presently available for birthdate determination, based on "pulse" or "cumulative" labeling with either tritiated thymidine (3HT) or bromodeoxyuridine (BrDU) incorporated into DNA during the mitotic cycle, allow only the approximate timing of terminal mitosis. To overcome this limitation, we have developed a "window labeling" technique based on the sequential administration of 3HT and BrDU. Chick retinal precursor cell cultures were first exposed to 3HT and, after a specified time interval, also to BrDU. After 6 days the cultures were fixed and processed for BrDU immunocytochemistry and 3HT autoradiography. Three populations of cells could be easily identified: (a) unlabeled cells, representing post-mitotic cells before label exposure; (b) BrDU-labeled cells [either 3HT (+)/BrDU (+) or 3HT (-)/BrDU (+)], representing those that continue dividing after the addition of BrDU; and (c) "window-labeled" cells, 3HT (+)/BrDU (-), which are those undergoing their last round of DNA synthesis during the interval between 3HT and BrDU administration. Control experiments demonstrated that this method allows birthdate determinations with a resolution of hours or minutes and is essentially free of deleterious effects on precursor cell survival and differentiation.

A visual pigment from chicken that resembles rhodopsin: amino acid sequence, gene structure, and functional expression

The amino acid sequence of a rhodopsin-like visual pigment from chickens has been determined by isolating and sequencing its gene. The predicted sequence is between 70% and 80% identical to bovine, human, and chicken rhodopsins and between 40% and 50% identical to human blue, green, and red cone pigments, the chicken red cone pigment, and cavefish long-wave cone pigments. The encoded pigment, produced by transfection of cDNA into cultured cells, absorbs maximally at 495 nm as determined from photobleaching difference spectra and reacts at 20 degrees C with 50 mM hydroxylamine with a half-time of 16 min. These properties, together with a high pI predicted from the amino acid sequence, suggest that this cloned gene encodes the chicken green pigment previously identified by biochemical and spectroscopic studies. This sequence defines a new branch of the visual pigment gene family.

Manifestations of pediatric AIDS: proposed mechanisms of transmission

Pediatric Acquired Immunodeficiency Syndrome (AIDS) is expected to increase by greater than 75% by 1993. Most of these infants will become infected with the Human Immunodeficiency Virus (HIV) through the mother. It is unclear exactly how the virus is passed from mother to child. The nature of HIV infection is described in this paper, and several mechanisms relevant to its transfer are proposed.

Childhood through the eyes of child psychiatrists and paediatricians

Attitudes to childhood in general and towards one's own childhood in particular are compared in a survey of 152 Australian and New Zealand child psychiatric and paediatric trainees. Results confirm the findings of Enzer et al that paediatricians view childhood more positively than do child psychiatrists. Although there is a significant difference between the two groups on measures of their perceptions of the parenting they received with child psychiatrists rating their own parents as less caring than do paediatricians, there is no relationship between attitudes to childhood and perceptions of the parenting they received. Implications of these findings are examined, both in terms of motivation for choosing one or other specialty and for the working relationship between the two professions.

Burns are different: the child psychiatrist on the pediatric burns ward

This article is written from the dual perspective of a child psychiatrist, consultant to a burn unit, who also happens to have suffered burns to his hands and face as the result of a car accident in 1976. One of its central themes is that burns are different from other surgical conditions. The role of the child psychiatrist as a consultant to a pediatric burn unit is explored and illustrated with clinical vignettes.

Toxicosis in sheep following ingestion of natural gas condensate

Thirty of 200 ewes died or were euthanatized during a 21-day period following a 1-day accidental exposure to natural gas condensate, a complex mixture of hydrocarbons obtained during collection of natural gas from wells. Despite access to potable well water, the poisoned ewes willingly consumed toxic doses of condensate that contaminated surface water. Eight animals died without premonitory signs; the remainder became ill over the course of a few days to 3 weeks. The principal cause of mortality was aspiration pneumonia, but myocardial degeneration and necrosis, renal tubular damage, gastritis, enteritis, and meningeal edema and hyperemia were also observed. Gas chromatographic analysis identified chemical traces of the hydrocarbons in the tissues, and "fingerprinting," the process of matching chromatographic tracings, provided forensic proof of the contamination source. Atomic absorption spectroscopy and cholinesterase analyses were performed to eliminate the possibility of toxicosis by heavy metal contaminants or other constituents. This appears to be the first reported incidence of natural gas condensate toxicity involving sheep or other ruminants. Although the available literature presents a suggestive pattern of clinical signs and pathologic lesions of petroleum product poisoning, diagnostic investigations should employ detailed analytic examination because each source of petroleum hydrocarbons contains unique sets of components that may produce different toxic effects.

Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice

A monoclonal antibody (designated SF25), which recognizes a protein antigen expressed on a large number of human colon carcinomas, was used for drug targeting. Daunomycin-antibody conjugates were prepared by two previously described procedures. In one, the drug was bound to the antibody through a spacer of small molecular mass (cis-aconitic acid), while in the other a dextran bridge served as the link between drug and antibody. High substitution rates of drug to antibody were obtained using the latter binding procedure. Both conjugates were tested in vitro against two human colon carcinoma cell lines, LS180 and KM-12. The efficacy of a daunomycin-dextran-SF25 antibody conjugate was tested against colon carcinoma LS180 tumors transplanted at different sites into athymic mice. The specific conjugate was significantly more inhibitory to a subcutaneous tumor growth than its components or their mixture. SF25 antibody alone showed antitumoral effects against all three forms of transplanted tumor tested, namely, local, metastatic or intrahepatic, whereas daunomycin, on its own, was effective only against the subcutaneous tumor. Binding of daunomycin to dextran partially improved its inhibitory activity against the metastatic tumor. The conjugate, daunomycin-dextran-SF25 antibody reduced the number of metastatic foci, increased the survival rate and delayed death. Yet against lymph node metastases it was not significantly better than a mixture of both constituents. However, results obtained with an intrahepatic tumor, a model that mimics the natural progression of the disease, resembled those described with the subcutaneous tumor. Daunomycin-dextran-SF25 antibody was significantly more effective than all components separately and than a mixture of drug and antibody, provided a highly drug-substituted conjugate was used.

Proteoglycan synthesis in cultures of murine retinal neurons and photoreceptors

1. In recent years, a number of histochemical and immunocytochemical studies have suggested that proteoglycans, particularly those in the interphotoreceptor matrix, exhibit altered distributions in several murine models for retinal degenerations. We are using a cell culture system to characterize the proteoglycans synthesized by neurons and photoreceptors derived from mouse retina, with the long-term goal of analyzing their role in retinal degenerations. 2. In this study we describe initial studies using cells derived from the retinas of normal mice. Cultures of retinal neurons and photoreceptors, which were free of glial, epithelia, or endothelial cells, were labeled with 3H-glucosamine and 35SO4. Proteoglycans isolated from the medium and cell layer were analyzed on the basis of charge, relative hydrodynamic size, and glycosaminoglycan content. 3. The studies indicate that the cultures actively synthesize proteoglycans. The medium contained predominantly chondroitin sulfate/dermatan sulfate, while the cell layer had a higher proportion of heparan sulfate, indicating a differential distribution between the two compartments.

Support services for pediatric trainees. A survey of training program directors

We conducted a survey of pediatric training program directors (75% response rate) regarding program support services for house staff, directors' attitudes about stress in training, and program plans to ameliorate such stress. Support services included explicit measures to alleviate stress, policies that may minimize stress, evaluation of house staff performance, feedback regarding career concerns, and benefits (eg, medical insurance and child care). Most programs offered services to reduce stress from training, but few offered preventive services. Support policies were reported to be inadequate, especially in the areas of coverage for leaves of absence. Maternity leave represented most leaves of absences, as 10% of the female house staff and 11% of the male house staff members became parents. Program directors' terms were short, and only 30% perceived these roles to be their primary roles. Male directors believed that female house officers had a harder time adjusting to their programs. We suggest changes and present a simple way for program directors to evaluate their support services.

Prevalence of HBsAg carriers in native and immigrant pregnant female populations in Israel and passive/active vaccination against HBV of newborns at risk

Israel has no official prevention policy at present against perinatal and horizontal transmission of hepatitis B virus (HBV) infection in newborns and children at risk. The present study was designed to assess the prevalence of HBV carrier state in a population of 11,123 pregnant women at term. Among this population (mean age 29.7 +/- 5.9), 98 women (0.88%) were found to be asymptomatic HBsAg+ carriers, and 97% of these carriers were anti-HBe+. Evidence for HBV replication, as determined by serum HBV-DNA, was established in 6.6% of the HBsAg+/anti-HBe+ population. The HBsAg carrier rate was strongly influenced by religion, continent, and country of birth of the carrier mothers. The highest relative carrier rate was found among women of Moslem origin (4.3%), as compared to Jewish women (0.67%). Most carrier women were born in Israel (56.1%) to mothers who had emigrated from regions with intermediate or high endemicity of HBV, such as North Africa or the Middle East. In these groups, the HBsAg carrier rate ranged between 1.2 and 3.0%. Ninety-three percent of newborns receiving passive/active vaccination against HBV developed protective levels of anti-HBs. Finally, evidence for horizontal transmission of HBV was found in 19.3% of 83 non-vaccinated children in families of HBsAg carriers. The present study therefore establishes HBsAg prevalence rates in specific risk groups of women at term and confirms the need for an official policy on immunization against HBV in Israel. Since over 50% of women at term belong to the defined risk groups, universal active vaccination of the entire newborn population each year is suggested as the most rational and needed policy in Israel.

Dose-related immunogenicity of Haemophilus influenzae type b capsular polysaccharide-Neisseria meningitidis outer membrane protein conjugate vaccine

We studied the immunologic responsiveness to Haemophilus influenzae type b capsular polysaccharide-Neisseria meningitidis group b outer membrane protein conjugate vaccine (PRP-NOMP) in children 2 to 42 months of age with vaccine dosages containing 7.5, 15, or 30 micrograms of PRP. Overall, PRP-NOMP was highly immunogenic. Geometric mean titers of anti-PRP antibody increased from 0.09 to 3.3 mg/L and 6.6 mg/L following each dose of vaccine, respectively, in the 2- to 18-month age group. Similarly, anti-PRP antibody geometric mean titers increased from 0.12 to 5.9 mg/L in the older than 18-month age group. However, we noted an apparent inverse relationship between vaccine dosages and immune responses following two doses of PRP-NOMP in 2- to 18-month-old children. Anti-PRP antibody geometric mean titers were 12.0, 6.9, and 3.5 mg/L, respectively, after the second dose of vaccine containing 7.5, 15, or 30 micrograms of PRP. Additional studies are needed to understand the mechanisms responsible for this inverse relationship and also to determine the optimal dosage of PRP-NOMP for young children.

Analysis of adenosine immunoreactivity, uptake, and release in purified cultures of developing chick embryo retinal neurons and photoreceptors

We have investigated the presence of endogenous adenosine and of mechanisms for adenosine uptake and release in chick embryo retinal neurons and photoreceptors grown in purified cultures in the absence of glial cells. Simultaneous autoradiographic and immunocytochemical analysis showed that endogenous adenosine and the uptake mechanism for this nucleoside colocalize in practically all the photoreceptors, but only in approximately 20% of the neurons. Approximately 25% of the neurons showed either immunocytochemical labeling or autoradiographic labeling, while greater than 50% of the neurons were unlabeled with both techniques. [3H]Adenosine uptake was saturable and could be inhibited by nitrobenzylthioinosine and dipyridamole and by pretreatment of the [3H]adenosine with adenosine deaminase. Although these observations indicate that the uptake is specific for adenosine, only 35% of accumulated radioactivity was associated with adenosine, with the remaining 65% representing inosine, hypoxanthine, and nucleotides plus uric acid. Adenosine as well as several of its metabolites were released by the cells under basal as well as K(+)-stimulated conditions. Potassium-enhanced release was blocked by 10 mM CoCl2 or in Ca2(+)-free, Mg2(+)-rich solutions. The results indicate that retinal cells that synthesize, store, and release adenosine differentiate early during embryogenesis and are therefore consistent with a hypothetical role for adenosine in retinal development.

Absence of bleeding on probing. An indicator of periodontal stability

Following active periodontal therapy, 41 patients were incorporated in a maintenance program for 2 1/2 years with recall intervals varying between 2-6 months. At the beginning of each maintenance visit, the periodontal tissues were evaluated using "bleeding on probing" (BOP). Reinstrumentation was only performed at sites which bled on probing. However, supragingival plaque and calculus was always removed. Pocket probing depths and probing attachment levels were recorded after active treatment and at the conclusion of the study. Progression of periodontal disease was defined by an observed loss of probing attachment of greater than or equal to 2 mm. The reliability of the BOP test as a predictor was evaluated by calculating sensitivity, specificity, accuracy, and positive and negative predictive values. While only a 29% sensitivity was calculated for frequent bleeding, the specificity was 88%. The fact that the positive predictive value for disease progression was only 6% and the negative predictive value was 98% renders continuous absence of BOP a reliable predictor for the maintenance of periodontal health.

[The dose-response relationship and time course of the neuromuscular blockade by alcuronium]

Although alcuronium has been in clinical use for almost 40 years, there is still considerable controversy in the literature regarding its neuromuscular blocking potency, the time course of the drug action and the side effects. The aim of this study was to investigate the dose-response relationship of alcuronium and to compare the time course of its neuromuscular effects with vecuronium following intubation doses of both compounds. METHODS. The study was carried out in two parts. In the first part 60 patients and in the second part 30 consenting ASA class I or II patients 20-60 years of age were included. The patients were undergoing elective gynecological or intra-abdominal operations. In the first part the patients received six different doses of alcuronium (60, 90, 120, 150, 180 or 210 micrograms/kg) in order to establish its dose-response relationship. Each dose was administered to ten patients. In the second part patients received either 300 micrograms/kg alcuronium (n = 15) or 100 micrograms/kg vecuronium (n = 15), and the time course of these two compounds (onset time, duration 25%, duration 75% and the recovery index) were compared. To test the reversibility, ten patients in each group received 30 micrograms/kg neostigmine at 25% recovery of T1. The neuromuscular effects of alcuronium and vecuronium were quantitated by EMG using the DATEX relaxograph. RESULTS. The log-logit analysis of the dose response data revealed an ED50 of 111 micrograms/kg and an ED95 of 250 micrograms/kg, which is in reasonable agreement with the measured effects following 120 micrograms/kg and 210 micrograms/kg alcuronium, resulting in 52 +/- 21% and 96 +/- 4% T1 depression, respectively. The onset time, duration 25%, duration 75% and spontaneous recovery index following 300 micrograms/kg alcuronium (5.0 +/- 3.4 min, 62 +/- 25 min, 119 +/- 38 min and 58 +/- 34 min) appeared to be significantly longer (P less than 0.05) than those observed after 100 micrograms/kg vecuronium (3.2 +/- 1.2 min, 33 +/- 7 min, 49 +/- 9 min and 18 +/- 7 min), respectively. The most striking finding of this study is the enormous individual variations observed in both neuromuscular potency and the time course of action of alcuronium. Following 150 micrograms/kg (routinely employed in daily clinical practice), the magnitude of T1 depression ranged between 19% and 100%. The same vast individual variations were observed in the time course of action following 300 micrograms/kg of alcuronium. The onset time, duration 25%, duration 75% and spontaneous recovery index ranged between 1.3 and 14 min, 22 and 110 min, 93 and 186 min and 32 and 116 min, respectively. CONCLUSIONS. The ED50 and ED95 values for alcuronium found in this study are in the same order of magnitude as 106.8 micrograms/kg and 135 micrograms/kg for ED50 and with 280 micrograms/kg for ED95, respectively, as reported by others. The long duration with slow recovery and the wide individual variation in the neuromuscular effects observed in our study have been reported earlier. Based on the above observations and because of the availability of better alternatives with fewer side effects, we conclude that alcuronium should be added to the list of obsolete neuromuscular blocking agents, together with gallamine and d-tubocurarine.