Reaction force exposure for tightening tool users: A psychophysical based experimental study of electric right-angle nutrunners

Reaction forces from nutrunner tools constitute a risk of developing MSDs. However, recommendations for sustainable reaction force levels are lacking. The aim of this study was to inform recommendations regarding reaction load exposures from right-angle nutrunners. Through a psychophysics approach, experienced assembly workers subjectively assessed reaction loads when using a nutrunner in six combinations of tool tightening strategy, work-pace and screw-joint stiffness. Electromyography, tool and joint parameters were measured. Regardless of tightening strategy, joint stiffness and work-pace combinations, no large differences in acceptable tightening torque, peak reaction force, and handle displacement were observed. However, acceptable jerk and impulse differed substantially between the TurboTight® (high-acceleration) and QuickStep® (conventional) tightening strategies. Although the TurboTight® strategy overall showed reduced peak muscular activities compared to the QuickStep®, the participant-rated acceptable torque levels were similar, plausibly due to TurboTights' high jerk levels. Jerk and impulse are hypothesized to influence the perception of reaction loads.

P5328Clinical and demographic predictors of attenuated LDL-C response to PCSK9 inhibition with bococizumab: Insights from the SPIRE trials

Background

While there exists significant inter-individual variability in low density lipoprotein cholesterol (LDL-C) response to proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition, predictors of this response remain uncertain. The Studies of PCSK9 Inhibition and the Reduction of Vascular Events (SPIRE) randomized control trials evaluated the efficacy of bococizumab, a humanized murine PCSK9 antibody, in patients at high cardiovascular risk.

Purpose

This study's purpose is to determine predictors of attenuated LDL-C response to bococizumab.

Methods

SPIRE 1 and 2 trial subjects allocated to bococizumab (n=13,675) were included. Subjects with an increase in LDL-C or non-compliance to bococizumab, or development of anti-drug or neutralizing antibodies were excluded. The remaining 8281 subjects were divided into quintiles of percent LDL-C reduction from baseline to 14 weeks. The first quintile (Q1) was considered an attenuated response. Multivariate logistic regression was used to discern significant predictors of attenuated response (Q1) compared to robust response (Q5).

Results

Q1 included 1657 subjects with median 35% LDL-C reduction (range 0.4% - 48%), whereas Q5 included 1658 subjects with median 83% LDL-C reduction (range 78% - 99%). Female sex, diabetes, white race, younger age, higher baseline non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein (a) [Lp(a)] and high-sensitivity C-reactive protein (hsCRP) were significantly associated with an attenuated response compared to a robust response (each p<0.05, Table).

Multivariate logistic regression for attenuated percent LDL-C response to bococizumab from baseline to 14 week Baseline characteristic Adjusted odds ratio (95% confidence interval) P-value Female 3.30 (2.72, 4.00) <0.0001 Diabetes 1.57 (1.32, 1.86) <0.0001 White race 1.44 (1.07, 1.93) 0.016 BMI (per 1kg/m2) 1.09 (1.07, 1.11) <0.0001 Age (per year) 0.98 (0.98, 0.99) 0.0005 Ln hs-CRP (per 1mg/L) 1.19 (1.11, 1.29) <0.0001 Lp (a) (per 10mg/dL) 1.11 (1.09, 1.14) <0.0001 Non-HDL-C (per 10mg/dL) 1.05 (1.02, 1.07) <0.0001 Odds ratios mutually adjusted for the listed variables.

Conclusions

In the SPIRE 1 and 2 trials, excluding subjects with anti-drug and neutralizing antibodies, significant predictors of an attenuated LDL-C response to PCSK9 inhibition with bococizumab included female sex, diabetes, younger age and white race.

Acknowledgement/Funding

Pfizer

GWAS for executive function and processing speed suggests involvement of the CADM2 gene

To identify common variants contributing to normal variation in two specific domains of cognitive functioning, we conducted a genome-wide association study (GWAS) of executive functioning and information processing speed in non-demented older adults from the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) consortium. Neuropsychological testing was available for 5429-32,070 subjects of European ancestry aged 45 years or older, free of dementia and clinical stroke at the time of cognitive testing from 20 cohorts in the discovery phase. We analyzed performance on the Trail Making Test parts A and B, the Letter Digit Substitution Test (LDST), the Digit Symbol Substitution Task (DSST), semantic and phonemic fluency tests, and the Stroop Color and Word Test. Replication was sought in 1311-21860 subjects from 20 independent cohorts. A significant association was observed in the discovery cohorts for the single-nucleotide polymorphism (SNP) rs17518584 (discovery P-value=3.12 × 10(-8)) and in the joint discovery and replication meta-analysis (P-value=3.28 × 10(-9) after adjustment for age, gender and education) in an intron of the gene cell adhesion molecule 2 (CADM2) for performance on the LDST/DSST. Rs17518584 is located about 170 kb upstream of the transcription start site of the major transcript for the CADM2 gene, but is within an intron of a variant transcript that includes an alternative first exon. The variant is associated with expression of CADM2 in the cingulate cortex (P-value=4 × 10(-4)). The protein encoded by CADM2 is involved in glutamate signaling (P-value=7.22 × 10(-15)), gamma-aminobutyric acid (GABA) transport (P-value=1.36 × 10(-11)) and neuron cell-cell adhesion (P-value=1.48 × 10(-13)). Our findings suggest that genetic variation in the CADM2 gene is associated with individual differences in information processing speed.

Metabolism of 4'-thio-beta-D-arabinofuranosylcytosine in CEM cells

Because of the excellent in vivo activity of 4'-thio-beta-D-arabinofuranosylcytosine (T-araC) against a variety of human solid tumors, we have studied its metabolism in CEM cells to determine how the biochemical pharmacology of this compound differs from that of beta-D-arabinofuranosylcytosine (araC). Although there were many quantitative differences in the metabolism of T-araC and araC, the basic mechanism of action of T-araC was similar to that of araC: it was phosphorylated to T-araC-5'-triphosphate (T-araCTP) and inhibited DNA synthesis. The major differences between these two compounds were: (i) T-araC was phosphorylated to active metabolites at 1% the rate of araC; (ii) T-araCTP was 10- to 20-fold more potent as an inhibitor of DNA synthesis than was the 5'-triphosphate of araC (araCTP); (iii) the half-life of T-araCTP was twice that of araCTP; (iv) the catalytic efficiency of T-araC with cytidine deaminase was 10% that of araC; and (v) the 5'-monophosphate of araC was a better substrate for deoxycytidine 5'-monophosphate deaminase than was the 5'-monophosphate of T-araC. Of these differences in the metabolism of these two compounds, we propose that the prolonged retention of T-araCTP is a major factor contributing to the activity of T-araC against solid tumors. The data in this study represent another example of how relatively small structural changes in nucleoside analogs can profoundly affect the biochemical activity.

A hypertensive reaction induced by concurrent use of selegiline and dopamine

OBJECTIVE

To describe a hypertensive reaction induced by concurrent use of selegiline and dopamine.

CASE SUMMARY

A 75-year-old critically ill white man who was receiving selegiline 5 mg twice daily for Parkinson's disease was initiated on an intravenous dopamine infusion for decreased urine output and hypotension. Within minutes of starting the dopamine infusion, the patient's systolic blood pressure increased from 105 to 228 mm Hg. Similar reactions occurred during two subsequent rechallenges.

DISCUSSION

Since monoamine oxidase is involved in the metabolism of catecholamines, selegiline may have affected the metabolism of the dopamine administered to the patient. Although selegiline is known to be a monoamine oxidase inhibitor specific for type B, evidence exists stating that selegiline may not be as specific as previously thought.

CONCLUSIONS

Dopamine should be used cautiously, if at all, in patients who are chronically receiving selegiline or who have received selegiline within the prior two weeks.

Metabolism of O6-propyl and N6-propyl-carbovir in CEM cells

The metabolism of O6-propyl-carbovir and N6-propyl-carbovir, two selective inhibitors of HIV replication, has been evaluated in CEM cells. Both compounds were phosphorylated in intact cells to carbovir-5'-triphosphate. The metabolism of these two agents was inhibited by deoxycoformycin and mycophenolic acid, but not erythro-9-(2-hydroxy-3-nonyl)adenine. No evidence of the 5'-triphosphate of either compound was detected in CEM cells.

Using the GOHAI to assess oral health status of frail homebound elders: reliability, sensitivity, and specificity

A pilot study assessed the clinically determined and self-reported oral health status of 50 randomly selected homebound patients served by Boston's Home Medical Service. The sample was largely female, low-income, and edentulous. The median age of the patients was 81 years (range, 64-101). While 76% deemed themselves to be in good to excellent oral health, 80% of the patients had not seen a dentist within the last two years, and 80% were found to be in need of routine dental care. To assess whether the Geriatric Oral Health Assessment Index (Atchison and Dolan, 1990) could be used by non-dental health professionals to determine the need for requesting dental consultation, the study physician repeated the administration of the GOHAI for 23 of the 50 subjects within eight weeks of the initial examination. For the 23 subjects having both dentist- and physician-administered GOHAI scores, the intraclass correlation coefficient was r = 0.61 (p = 0.002), indicating good agreement between the dentist's and physician's administrations of the GOHAI. However, given the high prevalence of need for care, the GOHAI appears to be of less value than an examination for identifying persons who need dental care in this population. Future research is needed to examine the GOHAI's sensitivity and specificity in populations with low to moderate prevalence of treatment need.

Comparison of the mechanism of cytotoxicity of 2-chloro-9-(2-deoxy-2- fluoro-beta-D-arabinofuranosyl)adenine, 2-chloro-9-(2-deoxy-2-fluoro- beta-D-ribofuranosyl)adenine, and 2-chloro-9-(2-deoxy-2,2-difluoro- beta-D-ribofuranosyl)adenine in CEM cells

In an effort to understand biochemical features that are important to the selective antitumor activity of 2-chloro-9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)adenine [Cl-F( upward arrow)-dAdo], we evaluated the biochemical pharmacology of three structurally similar compounds that have quite different antitumor activities. Cl-F( upward arrow)-dAdo was 50-fold more potent as an inhibitor of CEM cell growth than were either 2-chloro-9-(2-deoxy-2-fluoro-beta-D-ribofuranosyl)adenine [Cl-F( downward arrow)-dAdo] or 2-chloro-9-(2-deoxy-2, 2-difluoro-beta-D-ribofuranosyl)adenine [Cl-diF( upward arrow downward arrow)-dAdo]. The compounds were similar as substrates of deoxycytidine kinase. Similar amounts of their respective triphosphates accumulated in CEM cells, and the rate of disappearance of these metabolites was also similar. Cl-F( upward arrow)-dAdo was 10- to 30-fold more potent in its ability to inhibit the incorporation of cytidine into deoxycytidine nucleotides than either Cl-F( downward arrow)-dAdo or Cl-diF( upward arrow downward arrow)-dAdo, respectively, which indicated that ribonucleotide reductase was differentially inhibited by these three compounds. Thus, the differences in the cytotoxicity of these agents toward CEM cells were not related to quantitative differences in the phosphorylation of these agents to active forms but can mostly be accounted for by differences in the inhibition of ribonucleotide reductase activity. Furthermore, the inhibition of RNA and protein synthesis by Cl-F( downward arrow)-dAdo and Cl-diF( upward arrow downward arrow)-dAdo at concentrations similar to those required for the inhibition of DNA synthesis can help explain the poor antitumor selectivity of these two agents because all cells require RNA and protein synthesis.

Milestones in the development of Lym-1 therapy

Lym-1, a monoclonal antibody (MAb) that preferentially targets malignant lymphocytes, has induced therapeutic remissions in patients with advanced non-Hodgkin's lymphoma (NHL) or chronic lymphocytic leukemia (CLL) when labeled with iodine-131 (131I). Based on the strategy of fractionating the total radiation dose, trials were designed to define the safety, toxicity, and efficacy of a series of doses of 131I-Lym-1 given 2-6 weeks apart. All patients had disease resistant to standard therapy. 131I-Lym-1 was given after unconjugated Lym-1 and the 131I dose was escalated in Phase I-II trials. Therapy proved safe. The dose-limiting toxicity was thrombocytopenia. Nonhematological toxicities did not exceed grade 2 except for infrequent instances of grade 3 hypotension. In a low-dose (LD) trial of 131I-Lym-1, tumor regression occurred in 25 (83%) of 30 patients and 17 (57 %) had durable remissions; 3 of the remissions were complete. In a maximum tolerated dose (MTD) trial of 131I-Lym-1, 10 (71%) of 14 entries that received at least two doses of 131I-Lym-1 therapy and 11 (52%) of 21 total entries had remissions; 7 of the remissions were complete. All 3 entries in the MTD cohort of 100 mCi/m2 [3.7 MBq/m2] of body surface area had durable complete remissions. Therapeutic remission and human anti-mouse antibody (HAMA) after Lym-1 therapy were associated with increased survival that was significant in multivariate analyses. Evidence for an Ab3 idiotypic network with an antibody cytotoxic for Raji human lymphoma was found in the only patient examined in detail thus far; this patient was studied because she had a high titer, HAMA and prolonged survival. In conclusion, 131I-Lym-1 induced durable remissions in patients with chemotherapy-resistant NHL or CLL and was associated with acceptable toxicity. In a subset of the patients, survival was quite prolonged perhaps related to development of Ab3.

Metabolism and metabolic actions of 6-methylpurine and 2-fluoroadenine in human cells

Activation of purine nucleoside analogs by Escherichia coli purine nucleoside phosphorylase (PNP) is being evaluated as a suicide gene therapy strategy for the treatment of cancer. Because the mechanisms of action of two toxic purine bases, 6-methylpurine (MeP) and 2-fluoroadenine (F-Ade), that are generated by this approach are poorly understood, mechanistic studies were initiated to learn how these compounds differ from agents that are being used currently. The concentration of F-Ade, MeP, or 5-fluorouracil required to inhibit CEM cell growth by 50% after a 4-hr incubation was 0.15, 9, or 120 microM, respectively. F-Ade and MeP were also toxic to quiescent MRC-5, CEM, and Balb 3T3 cells. Treatment of CEM, MRC-5, or Balb 3T3 cells with either F-Ade or MeP resulted in the inhibition of protein, RNA, and DNA syntheses. CEM cells converted F-Ade and MeP to F-ATP and MeP-ribonucleoside triphosphate (MeP-R-TP), respectively. The half-life for disappearance of HeP-ribonucleoside triphosphate from CEM cells was approximately 48 hr, whereas the half-lives of F-ATP and ATP were approximately 5 hr. Both MeP and F-Ade were incorporated into the RNA and DNA of CEM cells. These studies indicated that the mechanisms of action of F-Ade and MeP were quite different from those of other anticancer agents, and suggested that the generation of these agents in tumor cells by E. coli PNP could result in significant advantages over those generated by either herpes simplex virus thymidine kinase or E. coli cytosine deaminase. These advantages include a novel mechanism of action resulting in toxicity to nonproliferating and proliferating tumor cells and the high potency of these agents during short-term treatment.

Polyamine pools in HIV-infected cells

The polyamines putrescine, spermine, and spermidine, present in all living cells, have been implicated in the replication of some herpesviruses and retroviruses, and elevated levels of these polyamines have been found in the lymphocytes of patients infected with HIV-1. We have examined the effect of HIV-1 infection on polyamine pools in cell culture. HIV-1 did not significantly affect the polyamine pools in CEM cells. Consistent with this observation, inhibitors of the two key enzymes of this pathway, ornithine decarboxylase and S-adenosylmethionine decarboxylase, did not prevent viral-induced cytopathic effects (CPE) in this cell line. Our results indicate that inhibitors of this pathway will not be therapeutically useful in the treatment of AIDS.

Elevated soluble fas production in SLE correlates with HLA status not with disease activity

Evidence from animal models of lupus suggests that disruption of Fas-mediated apoptotic events may play a role in systemic lupus erythematosus (SLE). The recently described secreted from of Fas (sFas) could interfere with apoptotic events by blockading Fas/Fas ligand interactions. We describe elevated secreted Fas protein in sera from 60 patients with SLE compared with controls but neither sFas protein nor sFas mRNA levels correlated with disease activity. At the mRNA level there is strong evidence that individuals with human leucocyte antigens common in SLE patients have a genetic predisposition for increased secreted Fas production.

Apoptosis in peripheral lymphocytes in systemic lupus erythematosus: a review

There is increasing evidence to suggest that abnormalities in apoptosis may play a part in the pathogenesis of systemic lupus erythematosus (SLE). For example, there is now considerable evidence that bel-2 expression is enhanced in a proportion of peripheral T cells, but not in B cells, in SLE patients and correlates with overall disease activity regardless of the activity index employed. Further work is required to establish whether enhanced bel-2 expression by some T cells in SLE patients is related to their activation or intrinsically enhanced by genetic predisposition. Mutations in Fas result in a lymphoproliferative syndrome and may play a role in accelerating autoimmune disease. A report of three children with mutations in Fas has once again focused attention on this regulator of apoptosis. The relationships between inducers and inhibitors of apoptosis may differ in different cell types, and must be elucidated before the implications of observations made in lymphocytes from SLE patients can be fully understood.

Resolution of CNS lesions following treatment of experimental allergic encephalomyelitis in macaques with monoclonal antibody to the CD18 leukocyte integrin

Experimental allergic encephalomyelitis (EAE) in macaques is an acute inflammatory and demyelinating disease of the central nervous system (CNS) which has been studied extensively as a model of the human demyelinating disease multiple sclerosis (MS). The in vivo administration of monoclonal antibodies against CD18, the common beta-chain of a leukocyte integrin, at the onset of clinical disease, significantly prolonged the survival of nine of 11 macaques (82%) and in some cases completely reversed the clinical appearance of disease. Treatment with anti-CD18 mAbs dramatically reduced the extent of inflammation in brain lesions as determined by magnetic resonance imaging (MRI). These improvements confirm that anti-CD18 mAbs are powerful anti-inflammatory agents in vivo and suggest that such mAbs may provide effective treatment of both demyelinating and inflammatory CNS diseases in man.

Lymphoma-selective antibody Lym-1 recognizes a discontinuous epitope on the light chain of HLA-DR10

The selectivity of Lym-1 for malignant B lymphocytes makes this monoclonal antibody a promising candidate for the delivery of toxic agents to malignant B cells. The original immunogen used for the development of Lym-1 was Raji Burkitt's lymphoma cell nuclei [Epstein A. L., Marder R. J., Winter J. N., Stathopoulos E., Chen F. M., Parker J. W., Taylor C. R. (1987) Cancer Res 47: 830]. The Lym-1 antigen was characterized at that time as a polymorphic HLA-DR variant. We prepared an affinity column using immobilized Lym-1 to isolate the Lym-1 antigen from Raji cell lysate. Immunological characterization of the immunoaffinity-purified Lym-1 antigen on Western blots led to the conclusion that the antigen is the beta chain of HLA-DR10. This was confirmed by Edman sequencing of the isolated polypeptide chain. Western blots further show that the Lym-1 epitope is only recognized if the beta chain disulfide bonds are intact. These results imply that Lym-1 binds a discontinuous epitope on the beta chain of HLA-DR10.

Metabolism and metabolic actions of 4'-thiothymidine in L1210 cells

4'-Thiothymidine (S-dThd) is a potent inhibitor of L1210 cell growth and is active against P388 leukemia in mice. Because of these activities and its novel structure, we have begun studies of its metabolism and metabolic actions in L1210 cells in order to understand its mechanism of cytotoxicity, S-dThd inhibited the incorporation of radiolabeled precursors into DNA, but did not inhibit the incorporation of either uridine or leucine into RNA or protein, respectively, which indicated that the mechanism of its toxicity was due to its inhibition of DNA synthesis. S-dThd did not decrease the concentration of any of the natural deoxynucleoside triphosphates, which indicated that its cytotoxicity was not due to the inhibition of ribonucleotide reductase. S-dThd was readily phosphorylated and used as a substrate for DNA synthesis. Because the rate of incorporation of S-dThd into DNA was 20% that of thymidine, it is likely that the mechanism of action of S-dThd is not due to inhibition of DNA polymerases by the 5'-triphosphate of S-dThd, but instead to its incorporation into the DNA and its subsequent disruption of some function of DNA.

Experimental allergic encephalomyelitis in non-human primates: diffusion imaging of acute and chronic brain lesions

Diffusion imaging and T2-weighted magnetic resonance imaging were performed on 16 monkeys with experimental allergic encephalomyelitis (EAE), a model of the human demyelinating disease MS. The purpose of this study was to determine whether local changes in diffusion image intensity could be correlated with the formation of acute and chronic demyelinating lesions. Diffusion image analysis was restricted to the internal capsule of the brain because of its anatomic orientation of fiber pathways. Acute inflammatory EAE lesions were large and monophasic, as visualized by T2-weighted MRI, and were accompanied by a decrease in the diffusion MR image signal with the diffusion-sensitizing gradient in all three orthogonal directions (n = 27 brain regions, P < 0.005). Chronic demyelinating lesions were preceded by multiple inflammatory attacks, as visualized by MRI, and by a decrease in diffusion MR image signal with the diffusion-sensitizing gradient in the two orthogonal directions perpendicular to the fibers of the internal capsule (n = 18 brain regions, P < 0.005). However, for the chronic group, there was no significant change in the diffusion MR image signal with diffusion-sensitizing gradient parallel to the fibers of the internal capsule at the terminal scan, suggesting little change in the water diffusion within the nerve fibers. These results suggest that diffusion imaging holds promise for measuring subtle changes in water diffusion due to different types of brain damage.

Bcl-2 expression is unaltered in unfractionated peripheral blood mononuclear cells in patients with systemic lupus erythematosus

It has been postulated that the high levels of autoantibodies observed in systemic lupus erythematosus (SLE) patients could result from abnormal longevity of polyclonally activated B-cells. This increased survival could be due to dysfunction of apoptosis, the normal regulatory process governing their life span. The protein product of the bcl-2 gene can enhance lymphoid cell survival by interfering with apoptosis. Moreover, transgenic mice overexpressing bcl-2 in their B-cells developed an autoimmune syndrome resembling SLE. To determine whether overexpression of bcl-2 occurs in SLE patients, bcl-2 protein was measured in peripheral blood mononuclear cells from 73 SLE patients, 20 healthy individuals and 47 patients with other autoimmune diseases. Only three lupus patients had raised levels of bcl-2 and there were no statistically significant differences in the mean bcl-2 levels measured in SLE patients compared to controls. Bcl-2 levels did not correlate with overall disease activity in SLE patients.

Experimental allergic encephalomyelitis in non-human primates: MRI and MRS may predict the type of brain damage

Volume-localized proton spectroscopy and T2-weighted MRI were performed on 23 monkeys with experimental allergic encephalomyelitis (EAE). The purpose of this study was to determine the relationships between temporal changes in lesion activity (measured on T2-weighted MRI), MRS [N-acetyl aspartate (NAA), creatine (CR), choline (CHO)], and the histologic definition of disease determined post-mortem. Animals were scanned in the same areas of the brain once a week before and after sensitization to myelin basic protein (BP). Histologic lesion types were predicted by a combination of preceding MRI and MRS measurements. Acutely fatal EAE lesions were large and monophasic as visualized by MRI, and increased CHO (p < 0.02, n = 16) and CHO/CR ratio (p < 0.001, n = 16) were detected by MRS at disease onset. Chronic EAE lesions were preceded by multiple inflammatory attacks as visualized by MRI and consistently low levels of NAA (p < 0.02, n = 13) and NAA/CR (p < 0.01, n = 13) which occurred after the initial attack. MRI negative brain regions (from animals that were sensitized to BP) were associated with low CHO/CR (p < 0.1, n = 5). The temporal correlation of MRI lesion activity and absolute MRS proton metabolites shows promise for predicting the subsequent duration and histologic type of lesions in EAE in non-human primates.

Disposition in mice of 7-hydroxystaurosporine, a protein kinase inhibitor with antitumor activity

UCN-01, a hydroxylated derivative of staurosporine, was selected for study because of its promising antitumor activity. For mice dosed intravenously, subcutaneously, or by oral gavage with this compound, the maximum tolerated doses (MTD) were 20, 10, and > 100 mg/kg, respectively. UCN-01 was stable in mouse and dog plasma, but in human plasma it was converted to a metabolite in a process not inhibited by standard protease and esterase inhibitors. Following an intravenous dose of 10 mg/kg UCN-01, the half-lives for the initial (t1/2 alpha) and terminal (t1/2 beta) exponential phases of elimination were 10 and 85 min, respectively; the area under the plasma concentration-time curve (AUC value) was 117 micrograms min ml-1. In mice dosed by oral gavage with 10 mg/kg, the calculated value for the half-life of the elimination phase was 150 min. The AUC value was 15 micrograms min ml-1, giving a value for bioavailability of 13%. After subcutaneous dosing with 10 mg/kg, the calculated values for half-lives for the distribution and elimination phases were 23 and 130 min, respectively; the AUC value was 113 micrograms min ml-1. Since this value is equivalent to that obtained for intravenous dosing, administration of UCN-01 by the subcutaneous route may be an alternative to intravenous dosing in preclinical and clinical trials.

Bcl-2 and Fas, molecules which influence apoptosis. A possible role in systemic lupus erythematosus?

Polyclonal B cell activation and the production of antibodies against a variety of autoantigens are features of systemic lupus erythematosus (SLE). Autoreactive B cells are found in healthy individuals but their numbers are probably regulated by cell death, after a few days, in the absence of proliferative stimuli. The process which achieves this regulation is known as apoptosis or programmed cell death. It has been postulated that in SLE patients dysfunction of apoptosis could result in the inappropriate longevity of autoreactive B cells, allowing autoantibody levels to reach pathogenic thresholds. This hypothesis has arisen as a result of studies revealing links between autoimmunity and two molecules which influence apoptosis. These are bcl-2 which enhances cell survival by inhibiting or delaying apoptosis and Fas, a cell surface molecule involved in the induction of apoptosis. Transgenic mice over expressing bcl-2 in their B cells showed polyclonal B cell expansion and their B cells showed extended survival in vitro. After a few months these mice developed an autoimmune syndrome resembling SLE. Mice that carry the lpr disorder have defects in the Fas gene. These mice, which do not express functional Fas molecules, suffer from an SLE-like autoimmune syndrome. Thus inappropriate expression of both bcl-2 and Fas can result in SLE-like autoimmune disease in mice. Research is now in progress to ascertain whether quantitative or functional abnormalities in these molecules exist in human SLE patients and contribute to the pathogenesis of the disease in some or all cases.

Phosphorylation of the enantiomers of the carbocyclic analog of 2'-deoxyguanosine in cells infected with herpes simplex virus type 1 and in uninfected cells. Lack of enantiomeric selectivity with the viral thymidine kinase

CdG, the carbocyclic analog of 2'-deoxyguanosine, is active against herpes, hepatitis B, and human cytomegaloviruses. We have studied the interaction of the tritiated enantiomers of CdG with the herpes simplex virus type 1-specific thymidine kinase (HSV-1 TK) and have examined their metabolism in uninfected and HSV-1-infected cells. D- and L-CdG were equally effective competitive inhibitors of the phosphorylation of thymidine (dThd) by the partially purified HSV-1 TK (Ki values were 2.1 and 3.4 microM, respectively) and were also equal as substrates (Km values were 17 and 26 microM, respectively, and Vmax values of the enantiomers were equal and about 50% greater than the Vmax for dThd). The partially purified enzyme preparation, which contained cellular nucleotide kinase activities (pyruvate kinase also was present in the assay medium), converted D-CdG almost exclusively to the triphosphate and L-CdG almost exclusively to the monophosphate. Similarly, in virus-infected cells the D-enantiomer was converted predominantly to the triphosphate and the L-enantiomer predominantly to the monophosphate. In uninfected cells the results were qualitatively similar. In CEM cells deoxycytidine (dCyd) kinase (EC 2.7.1.74) seemed to be the enzyme principally responsible for the phosphorylation of both enantiomers, as shown by competition studies. Thus, both the HSV-1 TK and cellular dCyd kinase (of CEM cells) showed no selectivity for the enantiomers of CdG. This lack of enantiomeric specificity has obvious implications for the design of inhibitors of both viral proliferation and cellular metabolism.

Purine nucleoside phosphorylase inhibitors: biochemical and pharmacological studies with 9-benzyl-9-deazaguanine and related compounds

Certain derivatives of 9-deazaguanine that contain arylmethyl, heteroarylmethyl or cycloalkylmethyl groups at the 9-position are potent inhibitors of purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1). To determine whether these agents can produce metabolically significant inhibition of PNP in cells and in animals, the authors performed pharmacological studies with a representative member of the series, 9-benzyl-9-deazaguanine (BzDAG). BzDAG was a potent inhibitor of PNP from calf spleen (Ki = 12 nM). It was also an effective inhibitor of PNP in cells and in animals as shown by the findings that it 1) inhibited the conversion of inosine to nucleotides in L1210 cells in culture at concentrations that had little effect on the utilization of hypoxanthine; 2) potentiated the toxicity of deoxyguanosine to CCRF-CEM cells in culture; 3) increased the pools of deoxy GTP in CCRF-CEM, Molt-3 and Molt-4 cells that had been treated with deoxyguanosine; 4) prevented the toxicity of 6-thioguanosine to HEp-2 cells in culture; 5) increased the plasma levels of endogenous inosine in rats; and 6) increased the plasma levels of 2',3'-dideoxyinosine in rats that had received BzDAG and dideoxyinosine in combination. Pharmacokinetic analysis of BzDAG in the rat showed it to be 48% orally bioavailable (at a dose of 5 mg/kg). About 95% of BzDAG was protein bound. After i.v. administration of BzDAG (5 mg/kg), more than 50% of the erythrocyte PNP was inhibited for 40 min. These results indicate that the 9-substituted-9-deazaguanines are potent orally active PNP inhibitors and are therefore of potential clinical interest as immunosuppressive and anti-inflammatory agents.

Metabolism of carbovir, a potent inhibitor of human immunodeficiency virus type 1, and its effects on cellular metabolism

Carbovir (CBV) [the (--)-enantiomer of the carbocyclic analog of 2',3'-dideoxy-2',3'-didehydroguanosine] is a potent inhibitor of human immunodeficiency virus type 1 (HIV) replication in vitro. We have characterized the metabolism of CBV and its effect on cellular metabolism in an effort to better understand its mechanism of action. CBV was primarily metabolized to the 5'-triphosphate of CBV (CBV-TP) to concentrations sufficient to inhibit HIV reverse transcriptase. Infection of CEM cells with HIV did not affect the metabolism of CBV. In CEM cells, there was no evidence of the degradation of CBV by purine nucleoside phosphorylase. The half-life of CBV-TP in CEM cells was 2.5 h, similar to that of the 5'-triphosphate of zidovudine (AZT). However, unlike the levels of the 5'-triphosphate of AZT, CBV-TP levels declined without evidence of a plateau. CBV did not affect the metabolism of AZT, and AZT did not affect the metabolism of CBV. A small amount of CBV was incorporated into DNA in intact CEM cells, and this incorporation was increased by incubation with mycophenolic acid, an inhibitor of IMP dehydrogenase. CBV specifically inhibited the incorporation of nucleic acid precursors into DNA but had no effect on the incorporation of radiolabeled precursors into RNA or protein. CBV did not decrease the level of TTP, dGTP, dCTP, or dATP. These results suggested that the cytotoxicity of CBV was due to the inhibition of DNA synthesis. Further studies are necessary to identify the target(s) responsible for growth inhibition.

Diffusion imaging of experimental allergic encephalomyelitis

Diffusion-weighted magnetic resonance imaging (MRI) was compared with T2-weighted MRI in longitudinal studies of experimental allergic encephalomyelitis (EAE), an animal model of multiple sclerosis, in five monkeys (Macaca fascicularis). In a region of the brain that had highly directional myelinated fibers (internal capsule) sequential changes were identified on diffusion-weighted images on and before the day these changes were detected on conventional T2-weighted images. Changes were also identified on diffusion-weighted images in brain areas that did not develop T2-weighted abnormalities. This result suggests that diffusion-weighted image intensities are sensitive to pathologic conditions of the brain that can not be seen on T2-weighted images.

Metabolism and disposition of a thiazolobenzimidazole active against human immunodeficiency virus-1

This study was undertaken to evaluate the disposition of the thiazolobenzimidazole, 1-(2,6-difluorophenyl)-1H,3H-thiazolo[3,4-a]benzimidazole (TZB), which has promising antiviral activity. For mice, the maximum tolerated intravenous dose of TZB was 50 mg/kg. An HPLC procedure developed for TZB was used to determine the distribution of the drug. TZB showed no measurable binding to plasma proteins. With intravenous dosing, the kinetic values for TZB in plasma and in each of five tissues were similar in that there was an initial, short alpha-phase (1.8-7.2 min) and a longer beta phase (38-68 min). The concentrations in liver were higher than those in plasma and other tissues. For mice dosed subcutaneously with TZB, the AUC value for plasma was considerably lower than that for mice dosed intravenously; mice dosed intraperitoneally had higher plasma levels of the drug than after oral or subcutaneous dosing. No intact drug could be detected in the plasma of mice dosed topically. After intravenous, oral, or subcutaneous dosing, urinary excretion of intact TZB was < 2% of the dose. Of several vehicles tested in an attempt to increase the plasma levels of unchanged TZB in mice dosed orally, 40% hydroxypropyl beta-cyclodextrin was most effective. Two metabolites present in plasma and urine of mice were tentatively identified as the axial and equatorial sulfoxide isomers of TZB; a third, minor metabolite, was tentatively designated as the sulfone. Although the compound has activity against HIV-1, its low solubility and extensive metabolism reduce its potential for clinical use.

Determination of absolute phosphate metabolite concentrations in RIF-1 tumors in vivo by 31P-1H-2H NMR spectroscopy using water as an internal intensity reference

The absolute metabolite quantification method of Thulborn and Ackerman [J. Magn. Reson. 55, 357 (1983)] in which the tissue water proton signal is used as an internal intensity standard and its more recent variation in which NMR peak intensities are referenced to that of the natural abundance deuterium signal of water [Li et al., SMRM Abstr. 2, 825 (1988); Song et al., Magn. Reson. Med. 25, 45 (1992) have been implemented to obtain absolute phosphate metabolite concentrations in subcutaneous RIF-1 tumors during untreated growth and following treatment with 5-fluorouracil. The equivalence of these two hydrogen isotopes as intensity standards and the validity of their use in the determination of absolute metabolite concentrations in vivo by NMR has been demonstrated. On matched in vivo and extract tumor samples (n = 5), excellent agreement has been obtained between nucleoside triphosphate concentrations determined by NMR and those derived by HPLC analysis for the control tumors. Following 3 days of untreated growth, absolute concentrations of phosphate metabolites in RIF-1 tumors (n = 10) decreased significantly, except for the Pi concentration which did not vary. For the treated tumors (n = 10) there were no changes in metabolite concentrations except for a decrease in the PCr and, possibly, Pi concentrations. The PCr/Pi ratio in the latter tumors did not change. These observations suggest that changes in absolute metabolite concentrations may be more sensitive indices of response to therapy than changes in metabolite peak amplitude ratios, a parameter commonly used to express in vivo NMR data.

Cross-reactive maternal autoantibodies and congenital heart block

Epitopes with linear sequences recognized by anti-La autoantibodies from seven mothers of children with congenital heart block were recently defined. Eight of these epitopes share sequence identity with three other proteins in addition to the original autoantigen, La. The three proteins are human cardiac myosin beta heavy chain, laminin B1 chain and the M6 protein of Streptococcus pyogenes. Affinity purified anti-La antibodies from a further three mothers bound to the La antigen and also to human cardiac myosin and mouse laminin. Affinity purified antibodies from three mothers of healthy children bound to the La antigen but showed minimal binding to either human cardiac myosin or mouse laminin. Cardiac myosin inhibited the binding of CHB-related anti-La antibodies to both La and myosin. These data support a role for maternal autoantibodies crossing the placenta and recognizing foetal cardiac antigens accessible at a critical developmental stage during gestation. We suggest that this would lead to complement fixation, inflammation and the subsequent pathology associated with congenital heart block.

Incorporation of the carbocyclic analog of 2'-deoxyguanosine into the DNA of herpes simplex virus and of HEp-2 cells infected with herpes simplex virus

The carbocyclic analog of 2'-deoxyguanosine (CdG) is active against herpes simplex virus (HSV), human cytomegalovirus, and human hepatitis-B virus. In order to understand the mechanism of action of this compound against HSV, we have evaluated (a) the incorporation of [3H]CdG into viral and host DNA in HEp-2 cells infected with HSV and (b) the interaction of the 5'-triphosphate of CdG (CdG-TP) with the HSV DNA polymerase and human DNA polymerases alpha, beta, and gamma (EC 2.7.7.7). Incubation of HSV-1-infected HEp-2 cells with [3H]CdG resulted in the incorporation of CdG into both the HSV and the host cell DNA. These results indicated that CdG-TP was used as a substrate for HSV DNA polymerase and for at least one of the cellular DNA polymerases. Degradation of both viral and host DNA with micrococcal nuclease and spleen phosphodiesterase indicated that CdG was incorporated primarily into internal positions in both DNAs. The viral DNA containing CdG sedimented in neutral and alkaline sucrose gradients in the same way as did viral DNA labeled with [3H]thymidine, indicating that the HSV DNA containing CdG was similar in size to untreated HSV DNA. CdG-TP was a competitive inhibitor of the incorporation of dGTP into DNA by the HSV DNA polymerase (Ki of 0.35 microM) and the human DNA polymerase alpha (Ki of 1 microM). CdG-TP was not a potent inhibitor of either DNA polymerase beta or gamma. Using DNA-sequencing technology, CdG-TP was found to be an efficient substrate for HSV DNA polymerase. Incorporation of CdG monophosphate (CdG-MP) into the DNA by HSV DNA polymerase did not interfere with subsequent chain extension. These results suggested that the antiviral activity of CdG was due to its incorporation into the DNA and subsequent disruption of viral functions. In contrast, CdG-TP was not as good as dGTP as a substrate for DNA synthesis by DNA polymerase alpha, and incorporation of CdG-MP by DNA polymerase alpha inhibited further DNA chain elongation.

Effects of 2-chloro-9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)adenine on K562 cellular metabolism and the inhibition of human ribonucleotide reductase and DNA polymerases by its 5'-triphosphate

2-Chloro-9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-adenine (Cl-F-ara-A) has activity against the P388 tumor in mice on several different schedules. Biochemical studies with a chronic myelogenous leukemia cell line (K562) grown in cell culture have been done in order to better understand its mechanism of action. Cl-F-ara-A was a potent inhibitor of K562 cell growth. Only 5 nM inhibited K562 cell growth by 50% after 72 h of continuous incubation. The 5'-triphosphate of Cl-F-ara-A was detected by strong anion exchange chromatography of the acid-soluble extract of K562 cells incubated with Cl-F-ara-A. Competition studies with natural nucleosides suggested that deoxycytidine kinase was the enzyme responsible for the metabolism to the monophosphate. Incubation of K562 cells for 4 h with 50 nM Cl-F-ara-A inhibited the incorporation of [3H]thymidine into the DNA by 50%. Incubation with 0.1, 1, or 10 microM Cl-F-ara-A for 4 h depressed dATP, dCTP, and dGTP pools but did not affect TTP pools. Similar inhibition of deoxyribonucleoside triphosphate pools was seen after incubation with 2-chloro-2'-deoxyadenosine. Both Cl-F-ara-ATP and Cl-dATP potently inhibited the reduction of ADP to dADP in crude extracts of K562 cells (concentration producing 50% inhibition, 65 nM). The effect of Cl-F-ara-ATP on human DNA polymerases alpha, beta, and gamma isolated from K562 cells grown in culture was determined and compared with those of Cl-dATP and 9-beta-D-arabinofuranosyl-2-fluoroadenine triphosphate (F-ara-ATP). Cl-F-ara-ATP was a potent inhibitor of DNA polymerase alpha. Inhibition of DNA polymerase alpha was competitive with respect to dATP (Ki of 1 microM). The three analogue triphosphates were incorporated into the DNA by DNA polymerase alpha as efficiently as dATP. The incorporation of Cl-F-ara-AMP inhibited the further elongation of the DNA chain, similarly to that seen after the incorporation of F-ara-AMP. Extension of the DNA chain after the incorporation of Cl-dAMP was not inhibited as much as it was with either Cl-F-ara-AMP or F-ara-AMP. Cl-F-ara-ATP was not a potent inhibitor of DNA polymerase beta, DNA polymerase gamma, or DNA primase.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of 7-(2-hydroxyethyl)guanine as a product of alkylation of calf thymus DNA with clomesone

Evidence at the molecular level is presented in support of alkylation of O6-guanine moieties of DNA as the mechanism of cytotoxicity of Clomesone to HT-29 cells and consists in the isolation and identification of a product resulting from alkylation of calf thymus DNA with Clomesone, followed by depurination to yield 7-(2-hydroxyethyl)guanine, whose formation is reasonably explained by O6-guanine chloroethylation followed by intramolecular alkylation at N7 of guanine and subsequent hydrolysis to the hydroxyethylguanine.

Disposition and metabolism of carbovir in mice dosed intravenously or orally

To determine the disposition of carbovir and [3H]carbovir in mice, HPLC and thin-layer chromatographic assays were developed and mice were dosed iv and by gavage. Carbovir had no lethal effect at iv doses up to 500 mg/kg and was stable for 24 hr in mouse plasma at temperatures ranging from 0-37 degrees C. Binding to plasma proteins was minimal. Following an iv dose of 500 mg/kg of carbovir or [3H] carbovir, elimination phases with half-lives of 26-37 min (alpha) and 206-330 min (beta) were observed for plasma. For mice dosed with 27 mg/kg of [3H]carbovir, however, only a single phase with a half-life of 17 min was noted. Of several tissues examined, kidney contained the highest concentration of radioactivity. For the high dose, 19.0 +/- 2.6% was excreted in the urine in 24 hr as unchanged carbovir and 42.2 +/- 2.4% as metabolites; for the low dose, 54.5 +/- 6.1% was excreted as carbovir and 26.5 +/- 5.0% as metabolites. When mice were dosed orally with 500 mg/kg, plasma concentrations of carbovir were low. The initial plasma half-life for carbovir was 69 min; the terminal half-life was 822 min. Urinary excretion of unchanged carbovir was 21.3 +/- 7.1%. These results indicate that clearance of high doses of carbovir is limited and that its absorption is poor after oral dosing.

Phosphorylation of the carbocyclic analog of 2'-deoxyguanosine in cells infected with herpes viruses

The carbocyclic analog of 2'-deoxyguanosine [(+-)-2-amino-1,9-dihydro-9-[(1 alpha,3 beta,4 alpha)-3-hydroxy-4-(hydroxymethyl)cyclopentyl]-6H-purine-6-one] (2'-CDG) is highly active in cell culture against strains S148 and E377 of herpes simplex virus type 1 (HSV-1), both of which code for thymidine kinase, and much less active against strain BW10168 which is deficient in this enzyme activity. Antiviral activity is associated primarily with the D-enantiomer; the L-enantiomer has much lower but significant activity. The metabolism of racemic 2'-CDG and its D- and L-enantiomers was studied in uninfected HEp-2 cells and in HEp-2 cells infected with the S148 or BW10168 strains of HSV-1. Nucleotides were separated by HPLC, and their elution was monitored by spectrophotometry. The chromatograms of extracts of cells infected with the S148 strain and treated with (+/-)-2'-CDG or D-2'-CDG included a new peak which appeared in the triphosphate region. This peak, the area of which exceeded that of the GTP peak, was shown to be due to the triphosphate of 2'-CDG. The new peak was not observed by HPLC of extracts of uninfected cells treated with (+/-)-2'-CDG or either of its enantiomers, cells infected with the S148 strain and treated with L-2'-CDG, or cells infected with the BW10168 strain and treated with (+/-)-2'-CDG or either of its enantiomers. The results were similar when these studies were performed with uninfected Vero cells and with Vero cells infected with strain S148 of HSV-1. In experiments with D-[8-3H]-2'-CDG, small amounts of phosphates of 2'-CDG could also be detected in uninfected HEp-2 cells and in cells infected with the BW10168 strain of HSV-1. Thus, 2'-CDG apparently is a good substrate for the virus-coded kinase and a very poor substrate for cellular phosphorylating enzymes. The selective phosphorylation of 2'-CDG by the virus-specific kinase presumably is critical for its antiviral activity as it is for that of acyclovir and other acyclic derivatives of guanine.

Autoantibody synthesis in salivary glands of Sjögren's syndrome patients

We investigated the possibility that autoantibodies are locally synthesized and secreted within salivary glands of patients with Sjögren's syndrome by measuring specific autoantibody as a proportion of the total immunoglobulin present both in serum and saliva. Of 25 patients studied, 21 showed salivary enrichment of IgA anti-La, in three cases IgA anti-La being detected in saliva when IgG anti-La was negative (by ELISA) in serum. Twenty-four showed enrichment of salivary rheumatoid factors and IgA and/or IgM carrying the 17-109 idiotype, a marker of kappa IIIb light chains. These data suggest that autoantibodies, especially of the IgA class, are synthesized primarily in salivary gland and that they can be detected in saliva before they become apparent in the peripheral circulation. The subsequent deposition of these antibodies within salivary glands may be a contributory factor to the pathogenesis of Sjögren's syndrome.

T-cell alterations in late postpoliomyelitis

The immunologic status of patients with prior poliomyelitis was studied using two-color flow cytometric analyses. Ten lymphocyte subsets including subsets of CD4+ T cells, CD8+ T cells, B cells, and natural killer cells were examined. Eighteen patients presented with clinical symptoms compatible with the postpolio syndrome. This group was compared with 18 asymptomatic postpolio survivors and 22 age-matched healthy controls. The results demonstrated significant alterations in CD4+ subsets in the postpolio group as a whole when compared with normal controls. These findings reveal definite alterations in the immune status of postpolio survivors and raise the possibility that immunologic factors may contribute to late disease progression.

Magnetic resonance imaging and peripheral blood abnormalities in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) was induced in twelve cynomologous macaques (Macaca fascicularis) by sensitization to autologous myelin basic protein (BP) in complete Freund's adjuvant (CFA). The white blood cell (WBC) count, absolute number of lymphocytes and absolute numbers of CD4+ and CD8+ T-cell subsets were measured weekly. Using magnetic resonance imaging (MRI), the animals were monitored twice weekly for the development of central nervous system (CNS) lesions. Conventional spin-warp imaging was performed using a General Electric CSI-II NMR imager/spectrometer (2 Tesla magnet). CNS lesions were detected by MRI in all of the animals sensitized to myelin BP. Longitudinal analysis of their peripheral blood leukocytes revealed a progressive leukocytosis and lymphopenia, which always preceded the onset of clinical signs and almost always also preceded the formation of detectable CNS lesions. These results suggest that frequent analysis of T-cell subsets may provide a more accurate means of predicting episodes of disease activity than clinical or MRI evaluation.

Fluctuations of CD4+ T-cell subsets in remitting-relapsing multiple sclerosis

Patients with multiple sclerosis (MS) frequently have selective depletion of the CD45R+CD4+ T-cell subset during active phases of disease. To study the relationship between changes in this subset and the onset of objective clinical exacerbations of disease, a longitudinal study was undertaken. Two CD4+ T-cell subsets and two CD8+ T-cell subsets were monitored by two-color immunofluorescence using a fluorescence-activated cell sorter. These subsets of peripheral blood lymphocytes were monitored monthly for one year in a group of 9 patients with remitting-relapsing MS and in 11 healthy age-matched control subjects. Significant changes in the ratio of two CD4+ T-cell subsets (CD45R-/CD45R+) were detected in 7 of 9 patients with MS, but not in any of the control subjects. Of those 7 persons, 4 suffered major clinical relapses substantiated by alterations in the neurological examination. The other 3 suffered minor relapses with subjective clinical abnormalities. All 7 had increased CD4+ T-cell subset ratios (%CD4+CD45R-/%CD4+CD45R+) within the month that new symptoms were reported. Most such increases resulted from a simultaneous depletion in the number of CD45R+CD4+ T cells and an increase in the number of CD45R-CD4+ T cells. One patient suffered a major relapse with no change in the ratio of CD4+ subsets but had a depletion of all CD4+ T cells. There were no consistent changes in any of the other subsets measured. These results indicate that a subgroup of patients with MS have abnormal fluctuations of two CD4+ T-cell subsets, which may correlate with increased disease activity.

Alterations in nucleotide pools induced by 3-deazaadenosine and related compounds. Role of adenylate deaminase

3-Deazaadenine, 3-deazaadenosine, and the carbocyclic analog of 3-deazaadenosine produced similar effects on nucleotide pools of L1210 cells in culture: each caused an increase in IMP and a decrease in adenine nucleotides and had no effect on nucleotides of uracil and cytosine. Concentrations of 50-100 microM were required to produce these effects. Although 3-deazaadenosine and carbocyclic 3-deazaadenosine are known to be potent inhibitors of adenosylhomocysteine hydrolase, the effects on nucleotide pools apparently are not mediated via this inhibition because they are also produced by the base, 3-deazaadenine, and because the concentrations required are higher than those required to inhibit the hydrolase. Cells grown in the presence of 3-deazaadenine or 3-deazaadenosine contained phosphates of 3-deazaadenosine (the mono- and triphosphates were isolated); from cells grown in the presence of the carbocyclic analog of 3-deazaadenosine, the monophosphate was isolated, but evidence for the presence of the triphosphate was not obtained. A cell-free supernatant fraction from L1210 cells supplemented with ATP catalyzed the formation of monophosphates from 3-deazaadenosine or carbocyclic 3-deazaadenosine, and a cell-free supernatant fraction supplemented with 5-phosphoribosyl 1-pyrophosphate (PRPP) catalyzed the formation of 3-deaza-AMP from 3-deazaadenine. Adenosine kinase apparently was not solely responsible for the phosphorylation of the nucleosides because a cell line that lacked this enzyme converted 3-deazaadenosine to phosphates. No evidence was obtained that the effects on nucleotide pools resulted from a block of the IMP-AMP conversion, but the results could be rationalized as a consequence of increased AMP deaminase activity. This explanation is supported by two observations: (a) coformycin, an inhibitor of AMP deaminase, prevented the effects on nucleotide pools, and (b) 3-deazaadenine decreased the conversion of carbocyclic adenosine to carbocyclic ATP and increased its conversion to carbocyclic GTP. The latter conversion requires the action of AMP deaminase and the observed effects can be rationalized by a nucleoside analog-mediated increase in AMP deaminase activity. Because these effects on nucleotide pools are produced only by concentrations higher than those required to inhibit adenosylhomocysteine hydrolase, they may not contribute significantly to the biological effects of 3-deazaadenosine or carbocyclic 3-deazaadenosine.(ABSTRACT TRUNCATED AT 400 WORDS)

Development of lymphocyte subsets in pigtailed macaques

The early development of eight lymphocyte subsets was determined for pigtailed macaque infants from 0 to 800 days of age using two-color flow cytometry and fluorescein- and R-phycoerythrin-conjugated monoclonal antibodies specific for human leukocyte antigens. Four major lymphocyte subsets in monkeys (B, CD4+ T, CD8+ T, and NK cells) could be further divided using two-color analysis. In neonates, the frequency of lymphocyte subpopulations having surface phenotypes found principally on dense, resting cells (IgD+ B cells, Lp220+ CD4+ T cells, and CD18dull CD8+ T cells) was much higher than subpopulations having phenotypes present principally on buoyant, activated cells (IgD- B cells, Lp220- CD4+ T cells, CD18bri CD8+ T cells). There was a complete absence of two CD18bri CD8+ subsets (CD8dull and CD8bri) during the first 300 days of life. The relative proportion of lymphocyte subsets with resting phenotype decreased with increasing age, while the subpopulations associated with activation gradually increased with age. These findings suggest that during early development immunocompetent cells gradually differentiate into activated lymphocytes.