The effect of N-terminal acetylation on Ca(2+)-ATPase inhibition by phospholamban

The peptide Ac-MEKVQYLTRSAIRRASTIEMPQQAR (Ac-PLB(1-25)) representing residues 1-25 of phospholamban (PLB) inhibited the maximal activity of the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum by about 53%, with a Kd value of 5 microM; the equivalent non-acetylated peptide PLB(1-25) had no effect. However, it was found that the non-acetylated peptide increased the effective Kd value for inhibition by Ac-PLB(1-25) consistent with competitive binding to the ATPase, with a Kd value of 8 microM for PLB(1-25). The non-acetylated peptide must therefore be able to bind to the ATPase, but in a conformation that does not lead to inhibition of the ATPase. The identity of the N-terminal residue is important in determining the strength of binding; replacement of the Met residue by Ile led to fourfold weaker binding, again with only binding of the acetylated peptide leading to inhibition of ATPase activity.

Utilization pattern and efficacy of nonsurgical techniques to establish drainage for high biliary obstruction

PURPOSE

To review the frequency and success of percutaneous and endoscopic techniques in the relief of high biliary obstruction.

MATERIALS AND METHODS

A search of the radiologic achieves was performed identifying 70 patients with cholangiographic demonstration of high biliary obstruction defined as proximal to the distal third of the extrahepatic bile duct. Record review determined the frequency and success rates of percutaneous and endoscopic techniques in providing biliary decompression for obstructive jaundice.

RESULTS

Endoscopic retrograde cholangiopancreatography was performed in 35 of 70 patients, providing initial endoscopic biliary decompression (EBD) in six patients (two subsequently required percutaneous intervention). Percutaneous biliary drainage (PBD) was attempted in 60 of 70 patients, providing initial decompression in 55 patients. PBD provided decompression after failed endoscopic biliary drainage in 18 of 26 patients. Endoscopic drainage was never attempted after failed percutaneous drainage. Overall EBD success was 23% and overall PBD success was 95%. The complication rate attributed to EBD was 26%; that attributed to PBD was 25%. For those patients who underwent attempts at both EBD and PBD, the complication rate was 16%.

CONCLUSION

At an institution with well-developed gastrointestinal medical services and interventional radiologic services, PBD was more successful in providing initial biliary decompression than endoscopic techniques for high biliary obstruction.

Metabolic responses during initial days of altitude acclimatization in the eastern Himalayas

The study was carried out on 16 men (aged 20-30 years) to evaluate daily metabolic responses during the early phase of altitude acclimatization at moderate altitudes between 3100 and 4200 m in the Eastern Himalayas. Resting (R) and submaximal exercise (E) oxygen consumption (IVO2) at 100 W at sea level (SL) were 3.25 (SEM 0.15) and 20.31 (SEM 0.77) ml/kg per min respectively. On day 1 at 3110 m both R and E IVO2 decreased (P < 0.001) and subsequently remained constant. At 3445 m these values tended to increase over the 3110 m values but were lower than the SL values. At 4177 m the decline in IVO2 was significantly greater (P < 0.01) than at the preceding altitudes. Pulmonary ventilation (IVE) increased consistently (P < 0.001) with increase in altitude. The arterial oxygen saturation (SaO2) at different altitudes was lower (P < 0.001) than SL values. The cardiac frequency (fC) at R and E was higher (P < 0.001) at altitude; the values at 3110 and 3445 m were significantly lower (P < 0.001) than at 4177 m. Blood pressure (BP) increased (P < 0.001) on the first day at each altitude. The systolic BP tended to decline towards SL values but the diastolic BP remained high (P < 0.001) throughout. The resting blood lactic acid concentration, [la-]bl, showed a decline (P < 0.001) only at 4177 m. The [la-]bl at E was similar at 3110 and 3445 m but was higher (P < 0.01) at 4177 m. These observations suggest that acclimatization to a mid-altitude of 3445 m can be safely avoided where rapid ascent to higher altitude is required.

Taxanes from in vitro cultures of the Himalayan yew Taxus wallichiana

Culture conditions have been standardized for initiation of callus cultures of Himalayan yew (Taxus wallichiana) using young stem and needle explants from mature trees. Cultures were established on a modified Murashige and Skoog's medium supplemented with various levels of auxins (2.4-D, NAA) and cytokinin (kinetin). A medium containing 0.25 mg/l kinetin and 5.0 mg/l 2.4-D was optimal for stem callus growth whereas the presence of 0.25 mg/l kinetin along with 3.0 mg/l NAA in the medium supported optimal needle callus growth. Growth of stem callus was faster than needle callus growth. Supplementation of ascorbic acid (30 mg/l) amongst various anti-phenolic agents tested significantly reduced browning of initiated callus. Two taxanes (2-deacetoxytaxinine 1 and 2'-deacetoxyaustrospicatine) known to occur in stem bark, have also been isolated from undifferentiated tissue of T. wallichiana in equal or higher yields, for the first time.

Age of illness onset and schizophrenic symptomatology during an inpatient washout period

The authors examine the relationship between the age of illness onset and the ability to tolerate a medication-free period in a sample of acutely ill schizophrenic patients. Patients were admitted to an inpatient research unit for the treatment of acute and recurrent psychiatric symptoms. Prior medications were discontinued upon admission to the unit for purposes of clinical research and behavioral assessment uncontaminated by medication side effects. The age of illness onset was significantly and positively correlated with the duration of hospital washout. Furthermore, age of illness onset was significantly correlated with the BPRS total score and the BPRS hostility/suspiciousness factor measured at the end of washout. Our results suggest that early onset schizophrenics deteriorate more rapidly in an acute episode than do their later age of onset counterparts.

Isolation and subcloning of chitinase clone from chickpea genomic library

Chickpea genomic library constructed earlier in phage lambda (EMBL-3) was screened for the presence of chitinase clone using tobacco chitinase cDNA as a probe. Positive clones obtained by primary screening of plaques (2 x 10(6)) were ascertained by secondary and tertiary screening. Presence of chitinase insert in the positive clones obtained, was further confirmed by restricting phage DNA with Sal I and then doing southern with tobacco chitinase. The insert band was eluted out and subcloned in puc 19 plasmid.

Molecular mapping and tagging of genes in crop plants

In India, molecular mapping and tagging of agronomically important genes using RFLP and RAPD markers have been carried out in three different crops: rice, mustard and chickpea. In rice, tagging of genes for resistance to gall midge and blast has been accomplished. Molecular mapping of cooking quality traits in rice is in progress. For fingerprinting rice cultivars, suitable probe enzyme combinations have been identified. In mustard, a partial RFLP linkage map has been constructed and one of the yellow seed-coat colour loci has been mapped. Significant associations of RFLP markers with quantitative traits have also been established. Potential use of RAPD markers to identify heterotic groups among mustard accessions has been demonstrated. In chickpea, the occurrence of considerable interspecific DNA polymorphism as revealed by RAPD analysis has facilitated construction of a partial linkage map.

Temporal expression of retinoic acid receptors in hamster fetus during organogenesis and alteration by retinoic acid treatment

Retinoic acid receptors alpha, beta and gamma (RAR alpha, beta, gamma) mRNAs from whole 8- to 15-day-old hamster fetuses were characterized and quantitated by Northern blots and solution hybridization using riboprobes from cloned hamster RAR cDNAs, derived from 12-day fetal hamster library. Two RAR alpha transcripts of approximately 3.1 and approximately 3.5 kb, one transcript of RAR beta approximately 2.8 kb and one transcript of RAR gamma approximately 3.1 kb were observed. The relative abundance levels of these transcripts were RAR gamma > beta > alpha. RAR beta and gamma levels peaked at day 11, increasing approximately 4-fold (beta) and approximately 2.5-fold (gamma) above their initial values at day 8. RAR alpha did not change appreciably and peaked on day 14 at 1.7 x of its lowest level at day 9. Regulation patterns of the three RARs diverged between days 8 and 9 and 13 and 14 postcoitum (p.c.) and coordinately increased between days 9 and 13 and decreased between days 14 and 15 p.c. In 12-day-old conceptuses exposed to all-trans-retinoic acid, RAR alpha did not increase significantly, but RAR beta increased 12-fold at 4 hr and RAR gamma 2-fold at 1 hr after the maternal treatments.

Combined transrectal sonographic and fluoroscopic guidance for deep pelvic abscess drainage

We attempted to determine the feasibility, safety, and success of transrectal catheter drainage of deep pelvic abscesses using a combination of transrectal sonography and fluoroscopic guidance. In this retrospective review of five cases, transrectal catheters were placed within abscess cavities over a 20 month period. Clinical improvement was prompt, catheters were removed within 7 days, and no complications were detected. No patient required further intervention (follow-up 2 to 20 months). Transrectal sonographically guided catheter drainage proved to be safe and effective in our series. This method is a promising alternative to the posterior (sciatic notch) approach when the anterior transabdominal approach is contraindicated.

Prediction of haloperidol steady-state levels in plasma after a single test dose

Because of large interindividual variabilities in the pharmacokinetics of haloperidol (HPDL), empirically adjusting the dose to achieve steady-state levels in plasma (Css) is a time-consuming process. We report a method to individualize dose to achieve a desired Css from an observed drug level 24 hours after a single 15-mg test dose of HPDL. Drug-free schizophrenic and schizo-affective patients were blindly and randomly assigned to achieve a low (< 5 ng/ml), medium (10-18 ng/ml), or high (> 25 ng/ml) Css range of HPDL. On day 1 of the study, each patient received an oral "test" dose of HPDL (15 mg), and blood was drawn 24 hours later to determine drug levels in plasma (C24h). The first 34 patients (group I) were then maintained empirically on 2, 5 to 8, or 10 to 15 mg twice daily of oral HPDL concentrate for 5 days to achieve a low, medium, or high Css range, respectively. For the next 58 patients (group II), the dose of HPDL to achieve the assigned Css range was computed by using C24h in a prediction formula. Application of the C24h correctly predicted the maintenance dose required to achieve the Css in 73.2% of the cases. Further, there was a highly significant correlation (R2 = 0.877, p < 0.0001) between the predicted dose and the actual dose required to achieve the targeted Css range. On the basis of these results, we have formulated a nomogram to help predict the maintenance dose required to achieve low, medium, or high HPDL targeted ranges at various C24h values.

Elevation of CSF somatostatin concentrations in mania

OBJECTIVE

The aim of this study was to compare levels of CSF somatostatin (somatotropin release-inhibiting factor) in drug-free patients with different major psychiatric disorders.

METHOD

CSF somatostatin concentrations were measured in 66 drug-free inpatients with Research Diagnostic Criteria diagnoses of schizophrenia, major depressive disorder, manic disorder, or schizoaffective disorder.

RESULTS

In comparison with both the patients with schizophrenia and the patients with schizoaffective disorder, the manic patients had markedly elevated CSF somatostatin concentrations. The depressed patients had significantly higher levels than the schizophrenic patients.

CONCLUSIONS

Mania is associated with relatively higher CSF somatostatin concentrations.

The hydrophilic domain of phospholamban inhibits the Ca(2+)-ATPase--the importance of the method of assay

The peptide MEKVQYLTRSAIRRASTIEMPQQAR-Cys representing residues 1-25 of phospholamban (PLN) decreases by 40% the maximal state rate of ATP hydrolysis by the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum (SR), measured at saturating concentrations of Ca2+. The pattern of Ca2+ uptake by SR vesicles in the presence of oxalate is complex, with an initial fast phase being followed by a lag phase and a second, slower phase of Ca2+ accumulation. PLN(1-25) reduces the rate of the slower phase of Ca2+ accumulation by 30%. However, if the level of accumulation of Ca2+ is measured after 2 min., the effect of PLN(1-25) is much less marked. It is concluded that PLN(1-25) inhibits the ATPase, but that the effects of this inhibition are not apparent under some assay conditions.

Constrained peptide analogues of transforming growth factor-alpha residues cysteine 21-32 are mitogenically active. Use of proline mimetics to enhance biological potency

Two proline mimetics, the enantiomers of 2-aza-bicyclo[2,2,1]heptane-3-carboxylic acid, have been incorporated in place of Pro30 into synthetic peptides based on the B-loop beta-sheet sequence of human transforming growth factor-alpha (TGF-alpha) (residues Cys21-Cys32). The peptides were further modified by inclusion of an N-terminal phenylalanine and constrained by formation of an intramolecular disulfide bond. While no mitogenic response was observed in the parental NR6 cell line, the peptides stimulated DNA synthesis in NR6/HER cells (NR6 fibroblasts transfected with the human epidermal growth factor receptor). Induction of DNA synthesis was dose dependent, with EC50 values in the range 130-330 microM; in the presence of low doses of TGF-alpha, the mitogenic effect of the peptides was additive, up to the plateau response achieved by maximal doses of TGF-alpha alone. These effects are consistent with the peptides acting via the same mechanism as TGF-alpha. Analysis of the structure of the peptides by NMR indicated that the presence of the mimetics significantly increased the propensity of the peptidyl-proline bond to adopt the cis conformation. These data confirm the role of the beta-sheet in receptor activation, and emphasize the importance of presentation of peptides in an appropriate conformation for recognition.

A study of immunoglobulins and complements (C3 & C4) in alopecia areata

Estimation of serum Immunoglobulins (IgG, IgM and IgA) and complements (C3 and C4) was carried out in 100 cases of alopecia areata as per method described by Mancini (1965).[1] Clinically patients were divided in two groups, alopecia areata circumscribed (group I) and severe alopecia areata (group II). Significant decrease in levels of one or more Immunoglobulins were observed in most of the patients. However, Serum complements (C3 and C4) were within range of normal control values.

Histochemical localization of retinoic acid receptors in the developing hamster fetus

Retinoids have pleiotropic effects on animal development. The eventual targets of retinoids are retinoic acid receptors (RARs). Therefore, developmental expression patterns of RARs are important in elucidating the mechanisms of normal functions of retinoids and retinoid-induced teratogenesis. We developed monospecific polyclonal antibodies against hRAR alpha, hRAR beta, and mRAR gamma, to study the developmental expression of RARs in hamster fetus. There was high sequence homology across the species for each subtype of RARs and antibodies raised against human or mouse RARs reacted with hamster RARs. In addition, hamster cDNA of RARs, which can generate the whole length antisense RNA probe using a suitable vector, were also isolated from a 12-day-old hamster fetal library. Monospecific antibodies and antisense RNA probes were used to localize proteins and transcripts of RARs in the developing hamster fetus from day 8 to day 14. There was a widespread distribution of RAR proteins and transcripts in the developing fetus. Expression was abundant in neuroepithelium, branchial arch, cardiac linings, and primordial bone and cartilage tissues. Overlapping expression and redundancy of various RARs may be one of the safeguard mechanisms in retinoid homeostasis.

Pharmacokinetics of the antiviral agent 3-deazaneplanocin A

The pharmacokinetics of 3-deazaneplanocin A (c3Nep), a competitive inhibitor of S-adenosyl-L-homocysteine (AdoHcy) hydrolase and novel antiviral agent, was investigated in female BALB/c mice. Animals were given a single intravenous dose of [3H]-c3Nep (0.1 mg/kg; 10 microCi), and blood and selected tissues were collected at various intervals thereafter for up to 72 h. The plasma concentration versus time data for c3Nep was best approximated by a two-compartment open model with first order elimination. The elimination half-life was 12.8 min, the area-under curve (AUC) was 3.38 micrograms.min.ml-1. The distribution of c3Nep into tissues was not extensive. Following 30, 120 min, and 24 h after dosing, the kidneys and the liver contained the highest amount of drug, but this amount did not exceed 1 microgram/g tissue. At these time periods, the majority of activity in the tissues represented labeled derivatives of c3Nep indicating that this compound was converted to stable metabolites. The presence of labeled conversion products in the blood confirmed that this drug is metabolized in vivo. The fact that c3Nep bound to plasma proteins in vitro may explain this drug's limited tissue distribution. The half-life and tissue distribution of c3Nep were different from those of carbocyclic 3-deazaadenosine, a related adenosine nucleoside antiviral drug and AdoHcy hydrolase inhibitor.

Angiokeratoma corporis diffusum

A case of angiokeratoma corporis diffusum having some classical features with dilatation of retinal vessels, but without urinary signs of renal involvement, is reported.

Localization of retinoic acid receptors in anterior-human embryo

Retinoic acid receptors (RARs) are nuclear transcription factors that are activated by all-trans-retinoic acid or 9-cis-retinoic acid and are found in all tissues but predominantly in developing fetus, dividing tumor cells, and adult skin. Three forms of these receptors, alpha, beta, and gamma, have been described. In this paper we report the presence of RAR alpha and beta determined by hybridization with anti-sense messenger RNA, and histochemical localization of the three forms of RARs using monospecific polyclonal antibodies in various tissues of early human embryos. In a 54-day-old embryo, RAR alpha was expressed primarily in the liver and the brain, with somewhat lesser expression in the intestine. RAR beta was the highest in the brain, followed by a restricted expression in the intestine and the liver. Other organs, i.e., adrenal, kidney, and testis, did not show measurable amounts of RAR beta. The immunohistochemical localization in anterior sections of a 43-day-old embryo indicated that RAR alpha was present in the neuroepithelial cells and in cells lining the primitive pharyngeal sac, dorsal aorta, and pericardium. RAR beta was somewhat less prevalent in same tissues, whereas the expression of RAR gamma was the lowest of the three RARs in any tissues examined. Results indicated that RAR alpha and beta appear at early stages of human embryonic development and their expression is restricted to certain types of tissues.

Platelet serotonin-2A receptors: a potential biological marker for suicidal behavior

OBJECTIVE

Abnormalities in the serotonergic system have been implicated in suicidal behavior. Higher numbers of serotonin-2 (5-HT2) receptors have been reported in the post-mortem brain of suicide victims. In order to further examine the role of 5-HT2A receptors in suicidal behavior, the authors studied 5-HT2A receptors in platelets of suicidal and nonsuicidal patients as well as normal comparison subjects.

METHOD

5-HT2A receptor levels were determined by using [125I]LSD as a radioligand in platelets obtained from hospitalized psychiatric patients (N = 131) and nonhospitalized normal comparison subjects (N = 40) during a drug-free baseline period. Patients were diagnosed according to DSM-III-R criteria, and suicidal behavior was identified by using the Hamilton Depression Rating Scale.

RESULTS

The mean maximum number of binding sites (Bmax) of platelet 5-HT2A receptors for all suicidal patients was significantly higher than for nonsuicidal patients or normal comparison subjects. This significant difference remained when subgroups of suicidal patients with depression, schizophrenia, schizoaffective disorder, or bipolar illness were compared to the other two subject groups. The higher number of platelet 5-HT2A receptors in suicidal patients was independent of diagnosis. While there was no significant difference in Bmax between patients with serious suicidal ideation and those who made suicidal attempts, both groups had significantly higher Bmax than normal comparison subjects.

CONCLUSIONS

The observed higher number of platelet 5-HT2A receptors in suicidal patients is independent of diagnosis and appears to be associated with both the brain and the platelets of suicidal patients. These results thus suggest the potential usefulness of platelet 5-HT2A receptors as a biological marker for identifying suicide-prone patients.

Cerebrospinal fluid levels of phenylacetic acid in mental illness: behavioral associations and response to neuroleptic treatment

Cerebrospinal fluid levels of phenylacetic acid (CSF PAA) were obtained from normal controls and from drug-free psychiatric inpatients (schizophrenia, major depression, mania, and schizoaffective disorder). Post-treatment CSF PAA levels were obtained from 16 patients after 4 weeks of neuroleptic treatment. Phenylacetic acid levels were higher in women and were significantly correlated with age. There were no differences in CSF PAA levels between the various diagnostic groups and no difference between the paranoid and the nonparanoid subtypes of schizophrenia. CSF PAA was significantly correlated with several measures of psychopathology, especially the Brief Psychiatric Rating Scale hostility/suspiciousness factor. Neuroleptic treatment did not result in significant PAA changes. These findings are discussed in light of the amphetamine-like role ascribed to phenylethylamine, the precursor of PAA.

Modulation of the receptor binding affinity of amphiregulin by modification of its carboxyl terminal tail

Amphiregulin (AR), a heparin-binding, epidermal growth factor (EGF) receptor ligand has homology with EGF but exhibits a lower affinity for the EGF receptor than EGF. As the mature form of AR is truncated at the C terminus and lacks a conserved leucine residue known to be essential for high affinity binding of EGF to the EGF receptor, wild-type AR (AR1-84), a C-terminally extended AR construct incorporating six residues from the predicted coding sequence of AR (AR1-90) and a similarly extended construct with a Met86 to Leu substitution (AR1-90(leu86)) were expressed as recombinant proteins in yeast, purified by heparin affinity and C18 reverse phase chromatography and their relative biological activities determined. The growth factors were tested in mitogenesis and EGF receptor autophosphorylation assays and their relative order of potencies was found to be leu86 > met86 > wt. The AR1-90(leu86) construct was found to be 50- to 100-fold more active than wild type AR1-84 consistent with previously reported studies of the role of the equivalent C-terminal leucine in EGF or TGF alpha. Significantly, the C-terminally extended form of AR, AR1-90, which utilized six residues from the predicted coding sequence, was 10-times more active than wild type AR1-84. This difference in activity of the C-terminally extended form of AR may be of biological significance since differential proteolytic processing of the AR precursor in vivo could result in production of multiple forms of the growth factor with differing affinities for the EGF receptor and hence differing biological potencies.

A study of peripheral T-Lymphocytes in alopecia areata

Estimation of peripheral T-lymphocytes (active and total) was carried out in 100 cases of alopecia areata as per method described by Boyam (1977) and West et al (1978). Clinically patients were divided in two groups, alopecia areata circumscribed (group I) and severe alopecia areata (group II). Thirty healthy subjects served as controls. Decrease in percentage of both active and total E-RFC was observed in 70% cases. The decrease was more significant in group II.

Transcriptional activation of a model reporter system by retinoids and retinoic acid receptor isoforms

Retinoic acid (RA) and its congeners mediate their biologic effects after binding to nuclear transcription factors called retinoic acid receptors. Biological effects and binding affinities to various receptors vary widely. Activation of transcription ability for selected retinoids was investigated using a standardized model system. CV-1 cells were cotransfected with a retinoic acid responsive reporter plasmid and expression vectors for retinoic acid receptors (RARs, alpha, beta or gamma) and/or retinoic X receptor (RXR alpha), and were treated with a retinoid (all-trans-RA, 13-cis-RA, Ro 12-4894, SRI 5898-21, or Ro 13-7410). Gene transcription for all retinoids tested was activated in a dose-dependent manner. All-trans-RA was the most potent activator of RAR alpha while SRI 5898-21 was the least active. RAR alpha and RAR beta showed similar levels of activation with all the retinoids tested, Ro 12-4894 and Ro 13-7410 induced little transcription in the presence of RAR gamma. Cotransfection of RXR alpha with the RARs changed the ability of the retinoids to activate transcription. Transcriptional activation in cells cotransfected with RXR and RAR beta or RAR gamma was lower than in cells cotransfected with RAR beta alone or RAR gamma alone. Such models with specific responsive elements may be useful for evaluating the relative activity of various retinoids in vitro, however, complex interactions are likely depending on the choice of the reporter construct and other transcription factors available in the cell.

Acneform eruptions and antitubercular drugs

Out of total 774 cases under antitubercular therapy only 11 cases (1.42%) developed acneform eruptions. Individual drugs found to cause these eruptions were Isoniazid (0.53%), Rifampicin (1.48%) and Ethambutol (0.63%).

Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors alpha (hRAR alpha), hRAR beta, and mouse RAR gamma (mRAR gamma) were expressed heterologously in Escherichia coli as a recombinant glutathione S-transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all-trans-retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST-hRAR alpha, 1.4 nM for GST-hRAR beta, and 3.3 nM for GST-mRAR gamma, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All-trans-RA and 4-oxo-all-trans-RA have high affinity with all three receptors (DC50 = 0.8-55 nM). The 13-cis RA binds to hRAR alpha with low affinity, but not to other RARs evaluated here. All-trans-N-ethylretinamide, all-trans-retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRAR alpha and mRAR gamma receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRAR beta binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.

Cerebrospinal fluid somatostatin concentrations in schizophrenia and schizoaffective disorder: the effects of antipsychotic treatment

The authors examined the effects of antipsychotic treatment on cerebrospinal fluid somatostatin like immunoreactivity (CSF SLI) in 14 schizophrenic and 3 schizoaffective patients. There was a modest but significant increase in CSF SLI in 13 out of the 14 schizophrenic patients. In addition, there was a significant positive correlation between duration of treatment and post-treatment CSF SLI concentrations. No differential response was noted in patients also treated with the anticholinergic benztropine.

A study of extra-auditory effects of noise

Paper mill workers (106) exposed to noise ranging from 80 to 96 dBA were assessed for alteration in clinical status. Neurobehavioral functions were examined with the help of a questionnaire. The study did not reveal any changes attributable to noise in subjects exposed to 86-90 dBA and > 90 DBA noise in course of their occupations.

CSF and plasma MHPG, and CSF MHPG index: pretreatment levels in diagnostic groups and response to somatic treatments

The authors report a significant positive correlation between levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) in cerebrospinal fluid (CSF) and plasma in drug-free affective disorder patients (major depression, mania, and schizoaffective disorder), but not in schizophrenia. Recent kinetic studies on the relationship between plasma and CSF MHPG discourage the interpretation of independent CSF MHPG levels without correction for the diffusion of MHPG across the blood-brain barrier. The authors therefore examine pretreatment CSF and plasma MHPG levels, and the CSF MHPG index (CSF MHPG corrected for by using simultaneously obtained plasma MHPG according to the method of Kopin et al. [1983]). No significant differences were found in these pretreatment MHPG measures among the four diagnostic groups. Changes in these MHPG indices, and their correlations with behavioral rating scores, are also examined with respect to response to the four major somatic therapies (neuroleptics, lithium, antidepressants, and electroconvulsive therapy).

Effects of aflatoxin B1 and T-2 toxin on the granulocyte-macrophage progenitor cells in mouse bone marrow cultures

Myelotoxic effects of aflatoxin B1 (AFB1) and T-2 toxin on the proliferation of the granulocyte-macrophage progenitor cells to granulocyte, macrophage and granulocyte-macrophage (GM) colonies were investigated in male CD-1 mice by a semisolid in vitro culture technique. Mice received 0, 0.03, 0.145 and 0.7 mg/kg or 0, 0.1, 0.5, and 2.5 mg/kg body weight of AFB1 and T-2 toxin, respectively, for 2 weeks on alternate days. Granulocyte, macrophage, and GM-colonies were suppressed in the group that received the highest dose of AFB1 (0.7 mg/kg body weight). Treatment with T-2 toxin activated granulocyte colonies at 0.5 mg/kg and macrophage colonies at 0.1 and 2.5 mg/kg but suppressed GM-colonies at 0.5 and 2.5 mg/kg body weight. Bone marrow cells from normal CD-1 mice were cultured with different concentrations of AFB1 (1-50 microM) or T-2 toxin (1-10 nM) in vitro. Significant activation of granulocyte colonies with 1 microM AFB1 and suppression of all three types of colonies with the highest concentration of AFB1 (50 microM) were observed. The suppression of granulocyte and GM-colonies associated with T-2 toxin was concentration-dependent. The greatest suppression occurred in macrophage colonies with three highest concentrations of T-2 toxin (3, 6, and 10 nM). Results suggest that AFB1 is myelotoxic both in vivo and in vitro, whereas T-2 toxin is more toxic in vitro.

Homovanillic acid in the cerebrospinal fluid: patterns of response after four weeks of neuroleptic treatment

Lumbar cerebrospinal fluid (CSF) homovanillic acid (HVA) concentrations were measured before and after 4 weeks of neuroleptic treatment in schizophrenic (n = 15) and schizoaffective (n = 4) patients. Neuroleptic treatment induced a nonsignificant (17%) increase in CSF HVA group mean levels. For the total group, no correlations were found between pretreatment CSF HVA and clinical measures, or between changes in HVA and clinical response. An alternative interpretation was attempted by defining "tolerant" and "nontolerant" subgroups. A "tolerant" response was defined as a reduction in posttreatment HVA values below pretreatment levels, whereas a "nontolerant" response was characterized by posttreatment values above pretreatment levels. When thus defined, nontolerant patients had a significantly inferior clinical response to neuroleptics, in contrast to their tolerant counterparts. Further, although there was no difference in pretreatment CSF HVA values between these two groups, pretreatment clinical profiles did differ significantly. Also, in a retrospective analysis, nontolerant patients were found to have a significantly earlier age of illness onset, a greater number of prior psychiatric hospitalizations, and more time spent in psychiatric hospitals.

Pharmacokinetics of the antiviral agent carbocyclic 3-deazaadenosine

The pharmacokinetics of carbocyclic 3-deazaadenosine (Cc3Ado), a competitive inhibitor of S-adenosyl-L-homocysteine hydrolase and novel antiviral agent, was investigated in female BALB/c mice. Mice were dosed either orally or intravenously with a single dose of 10 mg/kg (10 microCi [3H]Cc3Ado), and blood and tissue samples were taken at selected intervals for 24 hr. The plasma concentration vs. time data for Cc3Ado was best described by a two-compartment open model with first-order elimination. The apparent half-life was 23 and 38 min, for intravenously and orally administered Cc3Ado, respectively. Depending on route, tissue concentrations of Cc3Ado reached their maximum by 120 min, and concentrations of Cc3Ado were greatest in the liver, followed by the kidney, spleen, and stomach. By 24 hr, all tissues contained a similar amount of Cc3Ado. In the plasma, one major labeled metabolite was detected, which increased in concentration over time until about 45 min after dosing. None of the plasma Cc3Ado was protein bound, as assessed by in vitro protein binding analysis. Oral Cc3Ado was about 20% bioavailable. Data from this first investigation of the pharmacokinetics of Cc3Ado indicate that this antiviral agent is rapidly distributed and eliminated from the plasma and that distribution to tissues is widespread and rapid.

Platelet serotonin-2 receptors in schizophrenia: effects of illness and neuroleptic treatment

To examine the role of serotonin2 (5-hydroxytryptamine2, 5-HT2) receptors in schizophrenia, we determined the binding indices of 5-HT2 receptors using 125I-lysergic acid diethylamide (LSD) as the radioligand in platelets obtained from 40 normal control subjects and 42 drug-free schizophrenic patients. We also examined the effect of neuroleptic drug treatment on the binding parameters (Bmax and Kd) of 5-HT2 receptors in platelets of schizophrenic patients. We observed that the Bmax of 125I-LSD binding in platelets of schizophrenic patients was significantly higher than in platelets of normal subjects. There was no significant difference, however, between the Kd of 125I-LSD binding in platelets of schizophrenic patients and normal control subjects. Furthermore, we found no correlation between Brief Psychiatric Rating Scale scores and either Bmax or Kd of 125I-LSD binding at the end of the drug washout period. We also observed that neither treatment with haloperidol nor treatment with thiothixine caused significant changes in Bmax and Kd of 125I-LSD binding in platelets of schizophrenic patients. However, both fluphenazine and trifluoperazine did significantly increase the Bmax of 125I-LSD binding without any significant change in the Kd values in platelets of schizophrenic patients. Our results thus suggest that platelet 5-HT2 receptors are increased in schizophrenia and that chronic treatment with fluphenazine and trifluoperazine, but not haloperidol or thiothixine, further increases the 5-HT2 receptor binding sites in platelets of schizophrenic patients.

Regulation of an hepatic low-M(r) membrane-associated protein-tyrosine phosphatase

Protein-tyrosine phosphatases (PTPases), active against autophosphorylated insulin and epidermal growth factor (EGF) receptors in rat liver, are predominantly membrane associated. Fasting of rats for 48 h decreased hepatic particulate PTPase activity by 15.0-26.9%. This reduction in particulate PTPase activity was due to a rather specific decrease in activity of > 85% of a single species of PTPase, termed PTPase I. Disappearance of PTPase I activity from the particulate fraction was not accounted for by its translocation to the cytosol. PTPase I displayed the highest activity against autophosphorylated insulin and EGF receptors, relative to activity against a 32P-labelled peptide substrate, of three PTPases resolved from the liver particulate fraction. The M(r) value of PTPase I, as determined by gel filtration on a Superose 12 column was approx. 42,000, indicating that PTPase I belongs to the low-M(r) class of PTPases. An antibody raised against PTPase 1B, the prototype of this class of PTPases, did not react with PTPase I in Western blots. The potential importance of the novel change in activity of PTPase I in the regulation of insulin-receptor signal transduction is discussed.

Cooperativity during multiple phosphorylations catalyzed by rhodopsin kinase: supporting evidence using synthetic phosphopeptides

Rhodopsin kinase is a key component in the shutdown of visual transduction. The phosphorylation of rhodopsin's C-terminus was evaluated using synthetic peptides derived from the last 12 amino acids (337-348) as substrates and their phosphorylated counterparts as inhibitors. It was found that synthetic peptides were phosphorylated at the serine residue corresponding to Ser-343 in the primary sequence of bovine rhodopsin. The phosphopeptides were prepared by incorporating into the peptide chain a trityl-protected serine derivative at the site destined to contain the phosphoryl group. The trityl group was selectively released with 20% (v/v) dichloroacetic acid; the free hydroxyl group was then phosphitylated with di-tert-butyl N,N-diethylphosphoramidite, and the resulting phosphite derivative was oxidized with m-chloroperoxybenzoic acid. The phosphopeptides were found to have a greater affinity for the kinase compared with their nonphosphorylated counterparts; for the peptides corresponding to residues 337-348 of rhodopsin the affinity increased in the order VSKTETSQVAPA < VSKTETS[PO3H2]QVAPA < VS[PO3H2]KTETS[PO3H2]QVAPA. The results are interpreted to support the cooperativity hypotheses proposed previously [Wilden, U., & Kühn, H. (1982) Biochemistry 21, 3014-3022; Aton, B. R., Litman, B. J., & Jackson, M. L. (1984) Biochemistry 23, 1737-1741].

Modification of the retinoic acid signaling pathway by the catalytic subunit of protein kinase-A

Retinoic acid receptors (RARs) are ligand-activated nuclear transcription factors that belong to the steroid-thyroid hormone receptor superfamily. We have used the transient transfection of a retinoic acid-responsive reporter plasmid (RARECAT) to investigate the potential interactions between the retinoic acid (RA) and cAMP signaling pathways. Cotransfections of expression plasmids for the catalytic (C) subunits of cAMP-dependent protein kinase with RARECAT showed ligand-independent activation in both CV-1 and HeLa cells and a further 2-fold increase in RARECAT activity in the presence of RA. In CV-1 cells, cotransfections of the expression plasmids for RAR and the C-subunits produced increases in RARECAT activity (12- and 8-fold in the absence of ligand and 21- and 15-fold in the presence of RA for the C alpha- and C beta-isoforms, respectively). Cotransfections of both the C beta-subunit and RAR expression plasmids in HeLa cells produced 22- and 114-fold increases in RARECAT activity in the absence and presence of RA, respectively. These results provide evidence to suggest that the RA and cAMP signaling pathways are coupled, and signaling cross-talk may occur through the direct phosphorylation of RARs by the C-subunit as indicated by in vitro phosphorylation of the receptor.

Immunotoxicity of mycotoxins

The immune system is primarily responsible for defense against invading organisms. The effects of several mycotoxins on the immune responses have been investigated; however, most data concern laboratory animals. In some instances, farm animals and cells derived from livestock species have been employed to evaluate the immunotoxicity of mycotoxins. Immune responses are highly variable, and cost considerations usually preclude the use of dairy cattle as experimental models. Immunosuppression caused by aflatoxin B1 has been demonstrated in various livestock species (e.g., turkeys, chickens, and pigs) and also in laboratory animals (mice, guinea pigs, and rabbits). The response of bovine lymphocytes to aflatoxin in vitro is similar to that of other laboratory animals. Trichothecenes are potent immunosuppressive agents that directly affect immune cells and also modify immune responses as a consequence of tissue damage elsewhere. Sheep and calves treated with fusarium T-2 toxin develop leukopenia and decreased functioning of peripheral lymphocytes. Immunosuppressive effects of ochratoxin A, rubratoxin B, and patulin have been reported. Citrinin produced lymphopenia but stimulated responses against antigens. Antibodies against mycotoxins conjugated to proteins have been produced and are useful for analytical purposes.

Monoamine oxidase and cortisol response in depression and schizophrenia

The relationship between hypothalamic-pituitary-adrenal (HPA) axis function and platelet monoamine oxidase (MAO) activity was examined in drug-free depressed (n = 32) and schizophrenic (n = 36) inpatients. HPA function was measured by determining plasma cortisol levels at 8:30 a.m. and 11 p.m. before, and 8:30 a.m., 4 p.m., and 11 p.m. after administration of 1 mg of dexamethasone (DEX). There was a significant correlation between platelet MAO activity and all post-DEX cortisol levels (8:30 a.m., 4 a.m., and 11 p.m.) in depressed patients, and MAO activity and pre-DEX cortisol levels (11 p.m.) in schizophrenic patients. MAO activity was significantly higher in depressed DST nonsuppressors than in suppressors, and there were more DST nonsuppressors in high-MAO groups as compared with low-MAO groups. Our results thus suggest a strong relationship between platelet MAO activity and HPA function in depressed patients. These biochemical markers are potentially useful in the identification of biochemically and clinically homogeneous subgroups of depressed patients.

Immunological and neurobiochemical alterations induced by repeated oral exposure of phenol in mice

Phenol, a major metabolite of benzene, is a potentially immunotoxic and neurotoxic substance of environmental significance. Male CD-1 mice were continuously exposed to 0, 4.7, 19.5, and 95.2 mg phenol/l in drinking water for 4 weeks. Various immune functions were evaluated and levels of selected neurotransmitters and metabolites measured in discrete brain regions. The doses of phenol did not produce any overt clinical signs of toxicity; peripheral red blood cell counts and hematocrits decreased. A dose of 95.2 mg/l suppressed the stimulation of cultured splenic lymphocytes by lipopolysaccharide, pokeweed mitogen, and phytohemagglutinin and the response in mixed lymphocyte cultures. The two high doses suppressed antibody production response to the T cell-dependent antigen (sheep erythrocytes), as determined by plaque-forming cells, and serum antibody levels. Mice treated with phenol had lower levels of neurotransmitters in several brain regions. In the hypothalamus, a major norepinephrine-containing compartment, the concentrations of norepinephrine significantly decreased by 29 and 40% in groups dosed with 19.5 and 95.2 mg/l, while dopamine concentrations decreased in the corpus striatum by 21, 26, and 35% at 4.7, 19.5 and 95.2 mg/l, respectively. Phenol also decreased 5-hydroxytryptamine in the hypothalamus, medulla oblongata, midbrain and corpus striatum. Levels of monoamine metabolites decreased in the hypothalamus (5-hydroxyindoleacetic acid), midbrain (vanillylmandelic acid), corpus striatum (vanillylmandelic acid and dihydroxyphenylacetic acid), cortex (vanillylmandelic acid), and cerebellum (dihydroxyphenylacetic acid).

Acute lower gastrointestinal hemorrhage: treatment by superselective embolization with polyvinyl alcohol particles

OBJECTIVE

The major risk of transcatheter embolotherapy for acute hemorrhage in the lower gastrointestinal tract is irreversible intestinal ischemia. The authors studied the efficacy and safety of superselective transcatheter embolization with polyvinyl alcohol particles in arresting acute hemorrhage in the lower gastrointestinal tract.

SUBJECTS AND METHODS

All patients with clinical or scintigraphic evidence of acute hemorrhage in the lower gastrointestinal tract were considered for superselective embolization. The nine patients with angiograms that showed active hemorrhage in the lower gastrointestinal tract underwent the procedure. Superselective embolization was done through a 3-French catheter and was accomplished by using 100- to 590-microns polyvinyl alcohol particles. The segments of the intestinal tracts involved in the embolizations were examined for the presence of ischemia by endoscopy (n = 7) or histologic evaluation of a surgical specimen (n = 2) 2-44 days (mean, 11 days) after embolization or by clinical evaluation (n = 1).

RESULTS

The lesions treated by this method were located in the colon (n = 8) and jejunum (n = 1). Immediate hemostasis was achieved in every case. Three patients had recurrent lower gastrointestinal hemorrhage 1-24 days (mean, 9 days) after initial embolization. Two of these patients had surgery, while one had a successful second embolization. Two asymptomatic patients were found endoscopically to have small areas of ischemia involving only the mucosa. Only one patient was shown to have severe mucosal ischemia; this involved the colon in a distribution that suggested it was not caused by the embolization.

CONCLUSION

Ten superselective embolization procedures that used polyvinyl alcohol particles successfully controlled hemorrhage in the lower gastrointestinal tract in nine patients. In no case was intestinal infarction induced by the procedure, and only two endoscopically proved cases of asymptomatic mucosal ischemia occurred.

Definition of surface-exposed and trans-membranous regions of the (Ca(2+)-Mg2+)-ATPase of sarcoplasmic reticulum using anti-peptide antibodies

Peptides have been synthesized representing parts of the transduction, phosphorylation, nucleotide-binding and hinge domains of the (Ca(2+)-Mg2+)-ATPase of skeletal muscle sarcoplasmic reticulum (SR), and corresponding to segments of all of the postulated short inter-membranous loops of the (Ca(2+)-Mg2+)-ATPase (residues 77-88, 277-287, 780-791, 808-818, 915-924 and 949-958). A number of antibodies raised to these peptides have been shown to bind to the ATPase, defining surface-exposed regions. Many of these are concentrated in the phosphorylation and nucleotide-binding domains, suggesting that these domains could be exposed on the top surface of the ATPase. The cytoplasmic location of the loop containing residues 808-818 was confirmed by the finding that proteinase K treatment of intact SR vesicles enhanced the binding of antibodies against this segment. These findings support the 10-alpha-helix model of the ATPase. These results also suggest that only inter-membranous loops larger than about 20 residues are likely to be detected by immunological methods in transmembranous proteins. Binding of anti-peptide antibodies to proteolytic fragments of the ATPase has been used to define the domain structure of the enzyme. Some of the anti-peptide antibodies have been characterized by studying their binding to sets of hexameric peptides synthesized on plastic pegs. A wide pattern of responses is observed, with a restricted range of epitopes being recognized by each anti-peptide antibody.

Effects of N-ethyl,N-nitrosourea on monoamine concentrations and metabolizing enzymes in mouse brain regions

N-ethyl,N-nitrosourea is a well known alkylating agent and produces central nervous system-specific tumors in several laboratory animal species. In the present study, young male CD-1 mice were treated by i.p. injections of 0, 2, 8, or 32 mg/kg body weight N-ethyl,N-nitrosourea, twice a week for 3 weeks. Endogenous levels of brain monoamine neurotransmitters and their selected metabolites; norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), vanillylmandelic acid (VMA), dihydroxyphenyl acetic acid (dopac), homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and dihydroxyphenylalanine (dopa) were measured using HPLC with electrochemical detection. N-ethyl,N-nitrosourea treatment caused an increase of NE and 5-HT in the hypothalamus and striatum. Increased levels of 5-HIAA were noticed in the same brain regions. Elevated levels of NE were also observed in the cerebral cortex, medulla oblongata and the cerebellum. The major metabolite of NE, VMA, was decreased in several brain regions to non-detectable levels. Histopathological examination of brain tissue did not reveal any pathologic lesions. The increases in brain amines were associated with increased activity of tryptophan hydroxylase in the hypothalamus and corpus striatum. Dopa-decarboxylase was elevated in the cerebral cortex at a low dose of N-ethyl,N-nitrosourea only, whereas the monoamine oxidase activity was unaltered. Results indicated that N-ethyl,N-nitrosourea exposure may cause an elevation of steady state levels of various biogenic amines in brain areas and these changes to some extent are consistent with the altered activity of metabolizing enzymes.

Adjuvant activity of all-trans-retinoic acid in C57Bl/6 mice

The effects of all-trans-retinoic acid were investigated on the immune responses in C57Bl/6 mice after daily oral administration for one week. In selected experiments the immunosuppressive chemicals, cyclophosphamide and cyclosporin A were used in conjunction with retinoic acid. Retinoic acid stimulated the production of antibodies against sheep red blood cells and DNP-Ficoll; however, retinoic acid did not reverse the depression caused by immunosuppressive chemicals. In non-immunized animals retinoic acid stimulated the production of IL-1 but not of IL-2. The mitogenic responses of splenocytes against concanavalin A, phytohemagglutinin and pokeweed mitogen were depressed after the retinoic acid treatment; those against lipopolysaccharide were not influenced. Treatment with retinoic acid did not alter the mixed leukocyte responses but increased the activity of NK cells. Results indicate that retinoic acid may act as an adjuvant via activating macrophages, however, retinoic acid cannot reverse the immunosuppression induced by potent chemicals.

Structure-affinity relationships of retinoids with embryonic cellular retinoic acid-binding protein

Separation and quantitation of cellular retinoic acid-binding protein (CRABP) in embryonic and fetal hamster tissues was accomplished with high-performance size-exclusion chromatography. Binding affinity of 26 retinoids was established by in vitro displacement of high specific activity all-trans-[3H2]retinoic acid from fetal CRABP. The CRABP concentration in presomite-to-early somite (Day 8) hamster embryos was 1.9 pmol/mg cytosolic protein and increased to 7.5 pmol/mg protein in Day 13 fetuses; CRABP concentrations subsequently declined as gestation progressed. CRABP was located primarily in fetal brain and skin (5.8 +/- 0.3 and 2.2 +/- 0.1 pmol/mg protein, respectively), whereas only trace concentrations were found in fetal liver, placenta, and maternal uterus. Retinoids that could displace all-trans-retinoic acid from CRABP had a free acid at the polar terminus (or were carboxylate esters that were readily hydrolyzed to the corresponding free acid) and had a hydrophobic ring at the distal position. The ligand specificity of the CRABP studied here suggests that this protein was analogous to the CRABP I isoform. The in vitro binding affinities of teratogenic retinoids that competed for embryonic CRABP failed to correlate directly with relative teratogenic potency. In some instances, the latter observation can be related to extensive in vivo biotransformation of retinoids to multiple teratogenic metabolites and to retinoid persistence in the embryo. Three analogs containing a free carboxy terminus, SRI 5898-21, SRI 7323-78, and SRI 6153-40, were identified with high teratogenic potency but failed to bind fetal hamster CRABP. The structure-activity and binding data of the analogs studied here indicate that many, if not most, teratogenic retinoids (or their acidic metabolites) bind with embryonic/fetal CRABP, but the present data question the role for CRABP in their teratogenic mechanism of action.

Behavioral and biochemical effects of methylphenidate in schizophrenic and nonschizophrenic patients

The authors examined the specific behavioral and biochemical effects of intravenous methylphenidate in a sample of schizophrenic and nonschizophrenic patients. Twenty drug-free patients participated in a double-blind, placebo randomized study of methylphenidate, with multiple samples of plasma homovanillic acid (HVA) and serum growth hormone (GH) obtained during the infusion procedure. Methylphenidate caused a significant increase in positive symptoms that was relatively specific to the schizophrenic patients and was evident even in those with otherwise dormant symptomatology. When behavioral response was correlated with the biochemical responses (i.e., changes in plasma HVA and GH), there was a significant positive relationship between the increase in the BPRS-positive symptoms as well as the hostility/suspiciousness factor, and the increase in GH. These results suggest that the expression of psychotic symptoms may be associated with increased dopaminergic postsynaptic sensitivity, although the nonspecific nature of methylphenidate's actions discourages a stronger interpretation of the results.

Resistance of C57Bl/6 mice to immunosuppressive effects of aflatoxin B1 and relationship with neuroendocrine mechanisms

Aflatoxin B1 (AFB1) a secondary metabolite of Aspergillus flavus and A. parasiticus, is known for its carcinogenicity and immunosuppressive effects. We previously reported on the immunosuppressive effects of AFB1 in Swiss and CD-1 mice. This study concerned the involvement of the hypothalamus-pituitary-adrenal gland axis in the immunosuppressive effects of AFB1 in C57Bl/6 mice. Animals were treated orally with 30, 150 or 750 micrograms/kg AFB1 daily for four weeks. Splenic lymphocytes were assayed to investigate their phenotyping using flow cytometry, proliferative response against mitogens and allogeneic lymphocytes, cytolytic cell activity, and IL-2 production. Antibody-mediated immunocompetence was checked using sheep red blood cell (SRBC)-challenged animals by plaque-forming cell assay and enzyme-linked immunosorbent assay. The dose of AFB1 for the immunosuppressive effects on blastogenic response, IL-2 production, and primary antibody production of splenic cells was much higher than previous studies involving other mice strains. AFB1 decreased the amount of circulating anti-SRBC antibody, and the helper-T cell and B cell populations in phenotyping splenic lymphocytes. There were no significant changes in natural killer cell activity, mixed lymphocyte response, hypothalamic biogenic amine concentrations, and corticotropin releasing factor, and of adrenocorticotropic hormone and corticosterone in plasma. Results were confirmed using adrenalectomized mice. The hypothalamic-pituitary-adrenal axis does not appear to have a major role in AFB1-induced immunotoxicity.