Principles of proportional recovery after stroke generalize to neglect and aphasia.

BACKGROUND AND PURPOSE: Motor recovery after stroke can be characterized into two different patterns. A majority of patients recover about 70% of initial impairment, whereas some patients with severe initial deficits show little or no improvement. Here, we investigated whether recovery from visuospatial neglect and aphasia is also separated into two different groups and whether similar proportions of recovery can be expected for the two cognitive functions. METHODS: We assessed 35 patients with neglect and 14 patients with aphasia at 3 weeks and 3 months after stroke using standardized tests. Recovery patterns were classified with hierarchical clustering and the proportion of recovery was estimated from initial impairment using a linear regression analysis. RESULTS: Patients were reliably clustered into two different groups. For patients in the first cluster (n = 40), recovery followed a linear model where improvement was proportional to initial impairment and achieved 71% of maximal possible recovery for both cognitive deficits. Patients in the second cluster (n = 9) exhibited poor recovery (<25% of initial impairment). CONCLUSIONS: Our findings indicate that improvement from neglect or aphasia after stroke shows the same dichotomy and proportionality as observed in motor recovery. This is suggestive of common underlying principles of plasticity, which apply to motor and cognitive functions.

Cognitive-behavioural group therapy improves a psychophysiological marker of stress in caregivers of patients with Alzheimer's disease.

BACKGROUND: Family caregivers of patients with dementia frequently experience psychological stress, depression and disturbed psychophysiological activity, with increased levels of diurnal cortisol secretion. OBJECTIVES: To compare the effects of a cognitive-behavioural group therapy (CBT) to a psychoeducation group programme (EDUC) on cortisol secretion in caregivers of patients with moderate Alzheimer's disease (AD). METHOD: Caregivers of AD outpatients were semi-randomly allocated to one of two intervention programmes (CBT or EDUC) consisting of eight weekly sessions. Twenty-six participants completed the study. Before and after intervention, salivary cortisol was collected at four different times of the day. Effects of the interventions were evaluated with self-report psychological scales and questionnaires related to functional abilities and neuropsychiatric symptoms of the AD relative. RESULTS: Only in the CBT group did salivary cortisol levels significantly decrease after intervention, with a large effect size and high achieved power. Both groups reported a reduction of neuropsychiatric symptoms of their AD relative after intervention. CONCLUSION: Psychoeducation for caregivers may contribute to a reduction of neuropsychiatric symptoms of AD patients while CBT additionally attenuates psychophysiological responses to stressful situations in caregivers, by reducing diurnal cortisol levels. This may lead to a positive impact in the general health of the caregiver, eventually resulting in better care of the AD patient.

Frequency of Abnormally Low Neuropsychological Scores in Post-COVID-19 Syndrome: the Geneva COVID-COG Cohort.

OBJECTIVE: Several studies have reported poor long-term neuropsychological performances in patients following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but none has yet considered the effect of administering multiple intercorrelated neuropsychological tests and assessed the frequency of cognitive deficits in a normative population. Our aim was therefore to assess the presence of cumulative neuropsychological deficits in an actual post-coronavirus disease of 2019 (COVID-19) comparison group versus one simulated using Monte-Carlo methods. METHOD: Validated neuropsychological Monte-Carlo simulation methods were applied to scores from a battery of neuropsychological tests (memory, executive, attentional, perceptual, logical reasoning, language, and ideomotor praxis) administered to 121 patients who had had mild, moderate, or severe COVID-19 (mean age: 56.70 years; 32% women), 222 ± 43 days post-infection. The cumulative percentages of the three severity subgroups were compared with the results of a false discovery rate-corrected probability analysis based on normative data. RESULTS: The cumulative percentages of deficits in memory and executive functions among the severe and moderate patients were significantly higher than those estimated for the normative population. Moderate patients also had significantly more deficits in perception and logical reasoning. In contrast, the mild group did not have significantly more cumulative deficits. CONCLUSIONS: Moderate and severe forms of COVID-19 cause greater long-term neuropsychological deficits than those that would be found in a normative population, reinforcing the hypothesis of long-term effects of SARS-CoV-2 on cognitive function, independent of the severity of the initial infection.

Spontaneous confabulators fail to suppress currently irrelevant memory traces.

Human actions require integration of past experiences, ongoing percepts and future concepts. To adapt behavior to reality, the brain must identify mental representations of current relevance. Occasional amnesic subjects act according to invented stories ('spontaneous confabulations'), disregarding present reality. We used repeated runs of a continuous recognition task to measure the ability to distinguish currently relevant from previously encountered but currently irrelevant information. Spontaneous confabulators detected target items as accurately as nonconfabulating amnesics, but increasingly failed to suppress false-positive responses, confusing presentation in previous runs with presentation in the current run. Lesions involved the anterior limbic system: medial orbitofrontal cortex, basal forebrain, amygdala and perirhinal cortex or medial hypothalamus. We suggest that the anterior limbic system represents 'now' in human thinking by suppressing currently irrelevant mental associations.

Recovery from spontaneous confabulations parallels recovery of temporal confusion in memory.

BACKGROUND: In previous studies, the authors found that patients with spontaneous confabulation differ from those with nonconfabulating amnesia by 1) temporal context confusion (TCC) in memory based on an inability to suppress intrusions of currently irrelevant memory traces into ongoing thinking; and 2) lesions involving the orbitofrontal cortex, basal forebrain, or amygdala and perirhinal cortex. OBJECTIVES: To study the long-term clinical course of spontaneous confabulations, determine whether TCC in memory also parallels the clinical course of spontaneous confabulations, and study the impact of lesion site on clinical course. METHODS: Eight patients with spontaneous confabulation were re-examined 18 months after onset. Tests of memory and executive functioning and measurement of TCC in memory were again applied. MRI according to a standard protocol was performed to determine areas of permanent damage. RESULTS: Seven patients eventually stopped confabulating. TCC, but not common memory or executive tests, precisely paralleled the course of spontaneous confabulations. Patients with isolated, less extensive, orbitofrontal lesions stopped confabulating first and had the best neuropsychological outcome. Patients with basal forebrain lesions continued to confabulate for several months and remained amnesic. One patient with extensive orbitofrontal damage and perirhinal cortex damage continues to confabulate after more than 3 years, continuing to confuse memory traces. CONCLUSIONS: Temporal context confusion in memory is not only the sole feature reliably separating patients with spontaneous confabulation from those with nonconfabulating amnesia in the acute stage, it is also the only feature that precisely parallels the clinical course of spontaneous confabulations. Most patients eventually stop confabulating but duration of confabulations depends on the lesion site.

Hypothalamic amnesia with spontaneous confabulations: a clinicopathologic study.

Previous studies demonstrated that patients producing spontaneous confabulations fail to suppress currently irrelevant memory traces and have anterior limbic lesions, particularly involving the orbitofrontal cortex or the basal forebrain. Here, a woman is described who had sarcoidosis damaging the medial hypothalamus and endocrine dysfunction, and a severe memory failure characterized by spontaneous confabulation, disorientation, and severely impaired free recall with preserved recognition. Isolated hypothalamic damage may produce the same type of memory disorder as orbitofrontal damage.

Deoxy sugar analogues of triciribine: correlation of antiviral and antiproliferative activity with intracellular phosphorylation.

Triciribine (TCN) and triciribine monophosphate (TCN-P) have antiviral and antineoplastic activity at low micromolar or submicromolar concentrations. In an effort to improve and better understand this activity, we have conducted a structure-activity relationship study to explore requirements for the number of hydroxyl groups on the ribosyl moiety for biological activity. 2'-Deoxytriciribine (2'-dTCN), 3'-deoxytriciribine (3'-dTCN), 2', 3'-epoxytriciribine (2',3'-epoxyTCN), 2',3'-dideoxy-2', 3'-didehydrotriciribine (2',3'-d4TCN), and 2',3'-dideoxytriciribine (2',3'-ddTCN) were synthesized and evaluated for activity against human immunodeficiency virus (HIV-1), herpes simplex virus type 1 (HSV-1), and human cytomegalovirus (HCMV). Antiproliferative activity of the compounds also was tested in murine L1210 cells and three human tumor cell lines. All compounds were either less active than TCN and TCN-P or inactive at the highest concentration tested (100 microM) in both antiviral and antiproliferative assays. Reverse-phase HPLC of extracts from uninfected cells treated with the deoxytriciribine analogues only detected the conversion of 3'-dTCN and 2',3'-ddTCN to their respective monophosphates. Therefore, either the deoxytriciribine analogues were not transported across the cell membrane or, more likely, they were not substrates for a nucleoside kinase or phosphotransferase. We have concluded that the hydroxyl groups on the ribosyl ring system of TCN and TCN-P must be intact in order to obtain significant antiviral and antineoplastic activity.

6-N-Acyltriciribine analogues: structure-activity relationship between acyl carbon chain length and activity against HIV-1.

Triciribine (TCN) and triciribine-5'-monophosphate (TCN-P) are active against HIV-1 at submicromolar concentrations. In an effort to improve and better understand this activity, we have conducted a structure-activity relationship study to explore the tolerance of TCN to structural modifications at the 6-position. A number of 6-N-acyltriciribine analogues were synthesized and evaluated for antiviral activity and cytotoxicity. The cytotoxicity of these compounds was minimal in three human cell lines (KB, CEM-SS cells, and human foreskin fibroblasts (HFF)). The compounds were marginally active or inactive against herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV). In contrast, most of the compounds exhibited moderate to high activity against human immunodeficiency virus type 1 (HIV-1), IC(50)'s = 0.03 to 1 microM. This structure-activity relationship study identified the N-heptanoyl group as having the optimal carbon chain length. This compound was as active against HIV-1 as TCN and TCN-P. Reverse phase HPLC of extracts from uninfected cells treated with 6-N-acyltriciribines detected sufficient TCN-P to account for anti-HIV activity thereby suggesting a prodrug effect. Studies in an adenosine kinase deficient cell line showed that the 6-N-acyl derivative was not phosphorylated directly but first was metabolized to triciribine which then was converted to TCN-P.

Synthesis and antiviral evaluation of halogenated beta-D- and -L-erythrofuranosylbenzimidazoles.

A series of 2-substituted benzimidazole D- and L-erythrofuranosyl nucleosides were synthesized and tested for activity against herpesviruses and for cytotoxicity. The D-nucleosides 2,5, 6-trichloro-1-(beta-D-erythrofuranosyl)benzimidazole (8a) and 2-bromo-5,6-dichloro-1-(beta-D-erythrofuranosyl)benzimidazole (8b) were prepared by coupling 1,2,3-tri-O-acetyl-beta-D-erythrofuranose (D-6) with the appropriate benzimidazole, followed by removal of the acetyl protecting groups. The 2-isopropylamino (9), 2-cyclopropylamino (10), and 2-mercaptobenzyl (11) derivatives were synthesized by nucleophilic displacements of the C-2 chlorine in the benzimidazole moiety of 8a. The D-nucleoside 4-bromo-5, 6-dichloro-2-isopropylamino-1-(beta-D-erythrofuranosyl)benzimid azo le (17) was prepared by coupling D-6 with the appropriate benzimidazole. The L-erythrofuranosyl derivatives, 5, 6-dichloro-2-isopropylamino-1-(beta-L-erythrofuranosyl)benzimid azo le (21a), its 2-cyclopropylamino analogue (21b), and the 2-isopropylamino analogue (25), were prepared by coupling L-6 with the appropriate benzimidazole. Several of these new derivatives had very good activity against HCMV in plaque and yield reduction assays (IC(50) = 0.05-19 microM against the Towne strain of HCMV) and DNA hybridization assays. Very little activity was observed against other herpesviruses. This pattern is similar to the antiviral activity profile observed for the corresponding ribofuranosides 2,5, 6-trichloro-1-(beta-D-ribofuranosyl)benzimidazole (4a), its 2-bromo analogue (4b), and the 2-cyclopropylamino analogue (4c). In comparison, 8a was 15-fold more active against HCMV than 4a, and 8b was 4-fold more active against HCMV than 4b. The 5, 6-dichloro-2-isopropylamino-1-(beta-L-erythrofuranosyl)benzimid azo le (21a) was less active than 4c, which is now in clinical trials for HCMV infection. Both 8a,b had comparable HCMV activity to 4c. Mode of action studies with the D-erythrose analogues established that 8b acted by inhibition of viral DNA processing whereas 9 and 10 may act via a different mechanism. The lack of a 5'-hydroxymethyl group in all members of this series established that antiviral activity occurred without 5'-phosphorylation, a feature required for the activity of most nucleoside analogues.

Synthesis and antiproliferative and antiviral activity of 2'-deoxy-2'-fluoroarabinofuranosyl analogs of the nucleoside antibiotics toyocamycin and sangivamycin.

The glycosylation of 3,4-dicyano-2-[(ethoxymethylene)amino]pyrrole (7) with 2-deoxy-2-fluoro-alpha-D-erythro-pentofuranosyl bromide (2) furnished an anomeric mixture of nucleosides (8a,b). This mixture was separated, and the individual anomers were treated with methanolic ammonia to effect a concomitant deblocking and ring closure. This furnished both anomers of 2'-deoxy-2'-fluoro-ara-toyocamycin (9a,b). The cyano moiety of 9b was converted to the carboxamide moiety to furnish 2'-deoxy-2'-fluoro-ara-sangivamycin (10) and to the thiocarboxamide moiety to furnish 2'-deoxy-2'-fluoro-ara-thiosangivamycin (11). The target compounds 10 and 11 showed similar antiproliferative activity against L1210 cells in vitro, with IC50's of 3 and 5 microM. Antiviral evaluation revealed a somewhat different pattern of activity. All analogs, both alpha and beta anomers, were active against human cytomegalovirus (HCMV), albeit the beta anomers were most active. The beta anomers also were active against herpes simplex virus type 1 (HSV-1) and human immunodeficiency virus (HIV). Compound 10 was most active in the series, ca. 10-fold more potent than 11; IC50's for 10 ranged from 4 to 25 nM for HCMV, HIV, and varicella zoster virus (VZV) and from 30 to 500 nM for HSV-1. Even though compound 10 was cytotoxic, which will probably preclude its use as an antiviral drug (IC50's = 0.2-5.5 microM), the difference between cytotoxicity and activity against HCMV, HIV, and VZV was sufficient to indicate specific activity against a viral target.

Synthesis of non-nucleoside analogs of toyocamycin, sangivamycin, and thiosangivamycin: the effect of certain 4- and 4,6-substituents on the antiviral activity of pyrrolo[2,3-d]pyrimidines.

A number of 4-substituted 7-(ethoxymethyl)- and 7-[(2-methoxyethoxy)methyl]pyrrolo[2,3-d]-pyrimidine-5-carbonitrile and -5-thiocarboxamide derivatives and several 7-substituted 4,6-diaminopyrrolo[2,3-d]pyrimidine-5-carbonitrile, -5-carboxamide, and -5-thiocarboxamide analogs related to the nucleoside antibiotics toyocamycin and sangivamycin were prepared and tested for activity against human cytomegalovirus (HCMV) and herpes simplex virus type 1 (HSV-1). Biologically, modifications at the 4-position were not well tolerated in cell culture, and in almost all cases no activity against HCMV or HSV-1 was observed. Furthermore, none of the compounds inhibited the growth of L1210 murine leukemic cells in vitro. In sharp contrast to the 4-substituted compounds, all of the 4,6-diamino 5-nitrile and the 5-thioamide analogs were active against HCMV, whereas the 5-carboxamides were inactive. The corresponding 4-amino 6-methylamino and 6-dimethylamino 5-nitrile analogs were inactive against HCMV, establishing that an amino group at both C-4 and C-6 is a likely requirement for antiviral activity. Overall, our results demonstrate that an amino group at C-4 and a thioamide moiety at C-5 of a 7-substituted pyrrolo[2,3-d]pyrimidine are essential for activity against HCMV, whereas a 4,6-diamino analog does not necessarily require a thioamide group at C-5 for activity against HCMV.

(R)-(-)- and (S)-(+)-Synadenol: synthesis, absolute configuration, and enantioselectivity of antiviral effect.

Synthesis of (R)-(-)- and (S)-(+)-synadenol (1a and 2a, 95-96% ee) is described. Racemic synadenol (1a + 2a) was deaminated with adenosine deaminase to give (R)-(-)-synadenol (1a) and (S)-(+)-hypoxanthine derivative 5. Acetylation of the latter compound gave acetate 6. Reaction with N, N-dimethylchloromethyleneammonium chloride led to 6-chloropurine derivative 7. Ammonolysis furnished (S)-(+)-synadenol (2a). Absolute configuration of 1a was established by two methods: (i) synthesis from (R)-methylenecyclopropanecarboxylic acid (8) and (ii) X-ray diffraction of a single crystal of (-)-synadenol hydrochloride. Racemic methylenecyclopropanecarboxylic acid (10) was resolved by a modification of the described procedure. The R-enantiomer 8 was converted to ethyl ester 13 which was brominated to give vicinal dibromides 14. Reduction with diisobutylaluminum hydride then furnished alcohol 15 which was acetylated to the corresponding acetate 16. Alkylation-elimination procedure of adenine with 16 yielded acetates 17 and 18. Deprotection with ammonia afforded a mixture of Z- and E-isomers 1a and 19 of the R-configuration. Comparison with products 1a and 2a by chiral HPLC established the R-configuration of (-)-synadenol (1a). These results were confirmed by X-ray diffraction of a single crystal of (-)-synadenol hydrochloride. The latter forms a pseudosymmetric dimer with adenine-adenine base pairing in the lattice with the nucleobase in an anti-like conformation. Enantiomers 1a and 2a exhibit varied enantioselectivity toward different viruses. Both enantiomers are equipotent against human cytomegalovirus (HCMV) and varicella zoster virus (VZV). The S-enantiomer 2a is somewhat more effective than R-enantiomer 1a in herpes simplex virus 1 and 2 (HSV-1 and HSV-2) assays. By contrast, enantioselectivity of antiviral effect is reversed in Epstein-Barr virus (EBV) and human immunodeficiency virus type 1 (HIV-1) assays where the R-enantiomer 1a is preferred. In these assays, the S-enantiomer 2a is less effective (EBV) or devoid of activity (HIV-1).

(Z)- and (E)-2-((hydroxymethyl)cyclopropylidene)methyladenine and -guanine. New nucleoside analogues with a broad-spectrum antiviral activity.

New nucleoside analogues 14-17 based on a methylenecyclopropane structure were synthesized and evaluated for antiviral activity. Reaction of 2,3-dibromopropene (19) with adenine (18) led to bromoalkene 20, which was benzoylated to give N6,N6-dibenzoyl derivative 23. Attempts to convert 20 or 23 to bromocyclopropanes 21 and 22 by reaction with ethyl diazoacetate catalyzed by Rh2(OAc)4 were futile. By contrast, 2,3-dibromopropene (19) afforded smoothly (E)- and (Z)-dibromocyclopropane carboxylic esters 24 + 25. Alkylation of adenine (18) with 24 + 25 gave (E)- and (Z)-bromo derivatives 21 + 22. Base-catalyzed elimination of HBr resulted in the formation of (Z)- and (E)-methylenecyclopropanecarboxylic esters 26 + 27. More convenient one-pot alkylation-elimination of adenine (18) or 2-amino-6-chloropurine (30) with 24 + 25 afforded (Z)- and (E)-methylenecyclopropane derivatives 26 + 27 and 31 + 32. The Z-isomers were always predominant in these mixtures (Z/E approximately 2/1). Reduction of 26 + 27 and 31 + 32 with DIBALH afforded (Z)- and (E)-methylenecyclopropane alcohols 14 + 16 and 33 + 34. The latter were resolved directly by chromatography. Compounds 14 + 16 were converted to N6-(dimethylamino)methylene derivatives 28 and 29 which were separated and deprotected to give 14 and 16. Reaction of 33 and 34 with HCO2H led to guanine analogues 15 and 17. The 1H NMR spectra of the Z-analogues 14 and 15 are consistent with an anti-like conformation of the nucleobases. By contrast, 1H NMR and IR spectra of bromo ester 21 are indicative of syn-conformation of adenine. Several Z-(hydroxymethyl)methylenecyclopropanes exhibited in vitro antiviral activity in micromolar or submicromolar range against human and murine cytomegalovirus (HCMV and MCMV), Epstein-Barr virus (EBV), human herpes virus 6 (HHV-6), varicella zoster virus (VZV), and hepatitis B virus (HBV). Analogues 14, 15, and 33 were the most effective agents against HCMV (IC50 1-2.1, 0.04-2.1, and 0.8-5.6 microM), MCMV (IC50 2.1, 0.3, and 0.3 microM) and EBV in H-1 (IC50 0.2, 0.3, and 0.7 microM) and Daudi cells (IC50 3.2, 5.6, and 1.2 microM). Adenine analogue 14 was active against HBV (IC50 2 microM), VZV (IC50 2.5 microM), and HHV-6 (IC50 14 microM). Synadenol (14) and the E-isomer (16) were substrates of moderate efficiency for adenosine deaminase from calf intestine. The E-isomer 16 was more reactive than Z-isomer 14. The deamination of 14 effectively stopped at 50% conversion. Synadenol (14) was also deaminated by AMP deaminase from aspergillus sp.

Phosphorylation of triciribine is necessary for activity against HIV type 1.

Triciribine (TCN) is a tricyclic nucleoside with known antineoplastic and antiviral activity. It is a potent and selective inhibitor of HIV-1 and HIV-2, including strains known to be resistant to AZT or TIBO. TCN is phosphorylated to its 5'-monophosphate (TCN-P) by intracellular adenosine kinase (AK), but is not converted to di- or triphosphates. We now report that 5'-phosphorylation is requisite for the activity of TCN against HIV-1. CEM cells incubated with TCN at concentrations ranging from 0.1 to 330 microM gave intracellular TCN-P concentrations from 27 to 775 microM, respectively. There was no difference in the amount of intracellular TCN-P detected in uninfected compared with HIV-1-infected CEM cells. The antiviral effect of TCN against HIV-1 was strongly antagonized by the AK inhibitor 5-iodotubercidin (ITu). In contrast, TCN and ITu only exhibited additive cytotoxicity. The 5'-deoxy analog of TCN, which cannot be phosphorylated, had no antiviral effect against HIV-1 at a concentration more than 100 times higher than the IC50 of TCN. Similarly, TCN was not active against HIV-1 in an AK-deficient cell line (AA-2) at concentrations shown to inhibit the virus by >95% in CEM cells. Consistent with its AK-deficient phenotype, this cell line phosphorylated TCN to only 3% of the extent observed in CEM cells. We conclude that TCN must be phosphorylated to TCN-P for activity against HIV-1.

Synthesis and antiviral activity of phosphoralaninate derivatives of methylenecyclopropane analogues of nucleosides.

Phenylmethylphosphoro-L-alaninate prodrugs of antiviral Z-methylenecyclopropane nucleoside analogues and their inactive E-isomers were synthesized and evaluated for their antiviral activity against HCMV, HSV-1, HSV-2, HHV-6, EBV, VZV, HIV-1 and HBV. The adenine Z-analogue was a potent inhibitor of all these viruses but it displayed cellular toxicity. The guanine Z-derivative was active against HCMV, HBV, EBV and VZV and it was not cytotoxic. The 2,6-diaminopurine analogue was the most potent against HIV-1 and HBV and somewhat less against HHV-6, HCMV, EBV and VZV in a non-cytotoxic concentration range. The 2-amino-6-cyclopropylamino and 2-amino-6-methoxypurine prodrugs were also more active than parent analogues against several viruses but with a less favorable cytotoxicity profile. In the E-series of analogues, adenine derivative was active against HIV-1, HBV and EBV, and it was non-cytotoxic. The guanine analogue exhibited a significant effect only against HBV. The 2,6-diaminopurine E-analogue was inactive with the exception of a single EBV assay. The 2-amino-6-methoxypurine Z-methylenecyclopropane nucleoside analogue was an effective inhibitor of HCMV, MCMV and EBV. The 2,6-diaminopurine Z-prodrug seems to be the best candidate for further development.

Infection and replication of human cytomegalovirus in bone marrow stromal cells: effects on the production of IL-6, MIP-1alpha, and TGF-beta1.

We have investigated the mechanisms by which hematopoiesis is suppressed in patients suffering from human cytomegalovirus (HCMV) infections. Mixed populations of human bone marrow stromal and hematopoietic progenitor cells were inoculated with the Towne strain of HCMV to determine whether these populations could be infected and support HCMV replication. We found that the Towne strain of HCMV was capable of infecting and replicating in a mixed population of bone marrow stromal cells. We observed no significant alterations in bone marrow stromal cell proliferation or the production of IL-6, GM-CSF, soluble c-kit ligand and TNF-alpha following HCMV replication in either stimulated lipopolysaccharide (LPS) or unstimulated conditions. In samples of culture supernatants from LPS-stimulated HCMV-infected stromal cells, significant elevations in MIP-1alpha were observed. TGF-beta1 levels on the other hand exhibited two patterns following HCMV exposure; either TGF-beta1 levels decreased regardless of LPS stimulation or there was no effect. In addition, we observed that exposure to the Towne strain of HCMV resulted in significant inhibition of both granulocytic and erythrocytic colony formation in methylcellulose progenitor assays. Thus, both the direct effect of HCMV on hematopoietic progenitors as well as altered cytokine production by bone marrow stromal cells (including MIP-1alpha and TGF-beta1, but not IL-6) could contribute to hematopoietic failure during HCMV infection.

Probabilistic contingency learning with limbic or prefrontal damage.

A fundamental capacity of the human brain is to learn relations (contingencies) between environmental stimuli and the consequences of their occurrence. Some contingencies are probabilistic; that is, they predict an event in some situations but not in all. Animal studies suggest that damage to limbic structures or the prefrontal cortex may disturb probabilistic learning. The authors studied the learning of probabilistic contingencies in amnesic patients with limbic lesions, patients with prefrontal cortex damage, and healthy controls. Across 120 trials, participants learned contingent relations between spatial sequences and a button press. Amnesic patients had learning comparable to that of control subjects but failed to indicate what they had learned. Across the last 60 trials, amnesic patients and control subjects learned to avoid a noncontingent choice better than frontal patients. These results indicate that probabilistic learning does not depend on the brain structures supporting declarative memory.

Differences in DNA packaging genes and sensitivity to benzimidazole ribonucleosides between human cytomegalovirus strains AD169 and Towne.

The AD169 strain of human cytomegalovirus was approximately twofold more sensitive to polyhalogenated benzimidazole ribonucleosides than Towne strain. Sequence differences between the two strains have been identified in genes UL51, UL52, UL56, UL77, UL89 and UL104. Because these genes are involved in cleavage and packaging of viral DNA and the benzimidazole ribonucleosides inhibit this process, these sequence differences may be involved in the difference in drug sensitivity.

(Z)- and (E)-2-(hydroxymethylcyclopropylidene)-methylpurines and pyrimidines as antiviral agents.

Several Z- and E-methylenecyclopropane nucleoside analogues were synthesized and tested for antiviral activity in vitro against human and murine cytomegalovirus (HCMV, MCMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV), hepatitis B virus (HBV), herpes simplex virus types 1 and 2 (HSV-1, HSV-2), human herpesvirus 6 (HHV-6) and human immunodeficiency virus type 1 (HIV-1). The Z-2-amino-6-cyclopropylaminopurine analogue was the most effective agent against HCMV (EC50 or EC90 0.4-2 microM) followed by syncytol and the Z-2,6-diaminopurine analogues (EC50 or EC90 3.4-29 and 11-24 microM, respectively). The latter compound was also a strong inhibitor of MCMV (EC50 0.6 microM). Syncytol was the most potent against EBV (EC50 < 0.41 and 2.5 microM) followed by the Z-2,6-diaminopurine (EC50 1.5 and 6.9 microM) and the Z-2-amino-6-cyclopropyl-aminopurine derivative (EC50 11.8 microM). Syncytol was also most effective against VZV (EC50 3.6 microM). Activity against HSV-1, HSV-2 and HHV-6 was generally lower; synthymol had an EC50 of 2 microM against HSV-1 (ELISA) and 1.3 microM against EBV in Daudi cells but was inactive in other assays. The 2-amino-6-cyclopropylamino analogue displayed EC50 values between 215 and > 74 microM in HSV-1 and HSV-2 assays. 2-Amino-6-cyclopropylaminopurine and 2,6-diaminopurine derivatives were effective against HBV (EC50 2 and 10 microM, respectively), whereas none of the analogues inhibited HIV-1 at a higher virus load. Syncytol and the E isomer were equipotent against EBV in Daudi cells but the E isomer was much less effective in DNA hybridization assays. The E-2,6-diaminopurine analogue and E isomer of synthymol were devoid of antiviral activity.

Synthesis and enantioselectivity of the antiviral effects of (R,Z)-,(S,Z)-methylenecyclopropane analogues of purine nucleosides and phosphoralaninate prodrugs: influence of heterocyclic base, type of virus and host cells.

A series of R and S enantiomers of 2-aminopurine methylenecyclopropane analogues of nucleosides was synthesized. Two diastereoisomeric lipophilic phosphate prodrugs derived from R and S enantiomers of 2,6-diaminopurine analogue were also prepared. Enantioselectivity (diastereoselectivity in case of prodrugs) of in vitro antiviral effects was investigated with human and murine cytomegalovirus (HCMV and MCMV, respectively), herpes simplex virus types 1 and 2 (HSV-1 and HSV-2, respectively), human immunodeficiency virus type 1 (HIV-1), hepatitis B virus (HBV), Epstein-Barr virus (EBV) and varicella zoster virus (VZV). Strong differences in enantioselectivity were found between the R and S enantiomers of adenine analogue and enantiomeric 2-aminopurine analogues. Thus, the enantiomers of adenine analogue were equipotent against HCMV but not MCMV, where the S enantiomer is strongly preferred. The same S preference was found throughout the 2-aminopurine series for both HCMV and MCMV. In contrast, R-synadenol in HIV-1 assays was the best agent, whereas the S enantiomers of moderately effective 2-amino-6-cyclopropylamino and 2-amino-6-methoxypurine analogues were preferred. Little enantiomeric preference was found for R and S enantiomers of synadenol and the corresponding enantiomers of 2,6-diaminopurine analogue against HBV. A mixed pattern of enantioselectivity was observed for EBV depending on the type of host cells and assay. Against VZV, the R and S enantiomers of adenine analogue were equipotent or almost equipotent, but throughout the series of 2-aminopurine analogues a distinct preference for the S enantiomers was found. The stereoselectivity pattern of both diastereoisomeric prodrugs mostly followed enantioselectivity of the parent analogues. The varying enantioselectivities in the series of purine methylenecyclopropane analogues are probably a consequence of differences in the mechanisms of action in different virus/host cell systems.