Pseudo-outbreak of methicillin-resistant Staphylococcus aureus

OBJECTIVE

To determine whether a high rate of methicillin-resistant Staphylococcus aureus at our institution was due to laboratory misclassification and to evaluate the effect of this misclassification.

MATERIAL AND METHODS

We evaluated all S. aureus isolates identified at our institution during a 60-day period in 1997. Automated susceptibility test results (using the Vitek system) from our clinical microbiology laboratory and an independent laboratory were compared with oxacillin agar screen plate results at both laboratories. Isolates with discordant results for susceptibility to oxacillin were tested by broth microdilution minimal inhibitory concentrations and for the presence of the mecA gene.

RESULTS

Eighteen (72%) of the 25 organisms (obtained from 17 patients) found to be resistant to oxacillin by the Vitek system at our institution were susceptible by the oxacillin agar screen. Discordant isolates tested by broth microdilution minimal inhibitory concentrations and for the mecA gene were found to be oxacillin susceptible and mecA gene negative. Thus, at our hospital, almost three fourths of the organisms initially identified as methicillin-resistant S. aureus by the Vitek system were actually susceptible to oxacillin. This misclassification resulted in needless infection control measures and unnecessary vancomycin use.

CONCLUSION

Hospitals that use only automated susceptibility testing for S. aureus should periodically validate their results with additional testing.

Acute myo-inositol enhances swimming activity in goldfish (short communication)

Inositol in concentrations of 1-4 Mm (but not the control condition: mannitol-glucose) administered in aquarium water showed enhancement of swimming activity of goldfish after acute treatment (5 hours). These data support similar findings in rats. These data suggest that inositol may enhance motor activity which may be of relevance in neuropsychiatric disorders. Future studies of the effects of lithium on this activity, and its potential reversal by inositol may shed light on the possible involvement of the phosphatidyl-inositol second messenger system in this behavior.

Metronidazole and clarithromycin resistance amongst Helicobacter pylori isolates from a large metropolitan hospital in the United States

BACKGROUND

Metronidazole and clarithromycin-based therapies are among the most efficacious treatment regimens for H. pylori infection. Resistance to metronidazole or clarithromycin is associated with impaired therapy with these agents. We conducted a retrospective review of susceptibility data to determine the frequency of primary metronidazole and clarithromycin resistance among H. pylori isolates from a single metropolitan hospital in the United States. The database comprised 933 patients who presented at the Digestive Diseases Clinic at the Veterans Affairs Medical Center in Houston between September 1988 and January 1997 with complaints of dyspepsia, abdominal pain and peptic ulcer disease. One hundred and seventy-nine of these patients had both pharmaceutical records available for evaluation and culture and antimicrobial susceptibility data for analysis. The MICs were determined by both E-test and broth microdilution tests. The frequency of primary metronidazole resistance was 37.4% (67/179). The level of primary clarithromycin resistance was 6.1%. Dual metronidazole and clarithromycin resistance was present in approx. 3%. The high level of primary metronidazole and clarithromycin resistance in H. pylori isolates from this metropolitan hospital is such that antimicrobial susceptibility data should be available so that informed choice can be made for specific eradication therapies, especially in patients who fail treatment.

Hepatitis C virus genotypes and viremia and hepatocellular carcinoma in the United States

OBJECTIVE

Hepatitis C virus (HCV) is a well recognized cause of hepatocellular carcinoma (HCC). The pathogenic significance of HCV genotypes in hepatocarcinogenesis is undefined. The aim of this study was to investigate the genotypic distribution and viremic level of HCV in patients with HCV-associated cirrhosis with or without HCC.

METHODS

A total of 28 HCV-infected patients with HCC (HCC+) and 38 patients with HCV-associated cirrhosis without HCC (HCC-) were studied. HCV genotype was assessed by the genotype-specific polymerase chain reaction (PCR) method of Okamoto and restriction fragment length polymorphism (RFLP) of the 5' untranslated region (5' UTR). Hepatitis C viremia was quantitated with the branched-chain DNA (bDNA) assay.

RESULTS

Using the Okamoto method, we found genotype 1b in 64% of the HCC+ group and 74% of the HCC- group, 36% of the HCC+ group and 16% of the HCC- group were coinfected with a combination of genotype 1b and another genotype. Using the RFLP method, we found genotype 1b in 41% of the HCC+ group and in 24% of the HCC- group. Other genotypes accounted for 18% of the HCC+ group and 55% of the HCC- group; no combination genotypes were identified. Poor concordance occurred between the two genotyping methods. Mean bDNA levels were not significantly different between the two groups.

CONCLUSIONS

Our study demonstrates that no particular HCV genotypes were associated with HCC and genotype did not appear to influence the development of HCV-associated HCC.

A novel approach to observing articular cartilage deformation in vitro via magnetic resonance imaging

The design of a pressure cell that compresses a cartilage specimen in one dimension within an imaging magnet is presented. One-dimensional projection images in a direction perpendicular to the articular surface of the cartilage specimen were used to generate a uniaxial confined deformation creep curve for normal and trypsin-degraded cartilage specimens during a continuous 0.690 MPa (100 psi) pressure application. The resulting curves are shown to fit a two time constant viscoelastic model well and also indicate that the elastic modulus of cartilage decreases and the deformation rate increases upon trypsin proteolysis. Furthermore, cartilage permeability is shown as a function of cartilage strain for both the normal and trypsin-degraded case. Several two-dimensional slice-selective images were collected both before and after 80 minutes of continuous compression. These images were used to evaluate the relative changes in the spin-lattice, T1, and spin-spin, T2, relaxation time constant maps for both normal and degraded cartilage specimens in response to compression. The results of this study demonstrate the utility of a novel, non-magnetic, cartilage compression device and also support the validity of a simple two-component rheological model of articular cartilage.

Bcl-2 and p53 immunoprofile in Kaposi's sarcoma

Seventy three cases of Kaposi's sarcoma (KS) from the 3 histological subtypes (patch, plaque and nodular) were assessed for bcl-2 and p53 protein expression. The aim was to determine the level of expression of these proteins in KS and in the different subtypes. Commercially available antibodies to bcl-2 and p53 were applied after both microwave and pressure cooking antigen retrieval. Bcl-2 immunoexpression increased from the patch stage (36%) to the plaque stage (45%) to the nodular stage (70.83%). Better immunostaining for bcl-2 was obtained after pressure cooking. p53 on the other hand, was not expressed in the patch or plaque stages, but 54.16% of cases in the nodular stage were immunopositive. These results show a progression of immunoexpression of both bcl-2 and p53 from the early histological stages to the late tumor stage, implying that these proteins are upregulated late in the evolution of KS.

Detection of residual quadrupolar interaction in the human breast in vivo using sodium-23 multiple quantum spectroscopy

Sodium multiple quantum (MQ) spectroscopy of the human breast in vivo was performed. Double quantum (DQ) filtered spectra were used to demonstrate the existence of a non-vanishing (residual) quadrupolar interaction in the tissue. Triple quantum (TQ) filtered spectra were used to measure the two time constants associated with the biexponential transverse relaxation times of sodium in biological tissues. The two time constants were found to be 0.64 and 26.57 msec. The potential applications of this finding are discussed.

An MR imaging method for simultaneous measurement of gaseous diffusion constant and longitudinal relaxation time

A magnetic resonance imaging method for simultaneous and accurate determination of gaseous diffusion constant and longitudinal relaxation time is presented. The method is based on direct observation of diffusive motion. Initially, a slice-selective saturation of helium-3 (3He) spins was performed on a 3He/O2 phantom (9 atm/2 atm). A time-delay interval was introduced after saturation, allowing spins to diffuse in and out of the labeled slice. Following the delay interval a one-dimensional (1-D) projection image of the phantom was acquired. A series of 21 images was collected, each subsequent image having been acquired with an increased delay interval. Gradual spreading of the slice boundaries due to diffusion was thus observed. The projection profiles were fit to a solution of the Bloch equation corrected for diffusive motion. The fitting procedure yielded a value of D3He = 0.1562+/-0.0013 cm2/s, in good agreement with a measurement obtained with a modified version of the standard pulsed-field gradient technique. The method also enabled us to accurately measure the longitudinal relaxation of 3He spins by fitting the change of the total area under the projection profiles to an exponential. A value of T1 = 1.67 s (2 T field) was recorded, in excellent agreement with an inversion recovery measurement.

Sodium NMR evaluation of articular cartilage degradation

One of the first effects of degenerative osteoarthritis is the loss of proteoglycans from the matrix of articular cartilage. Using a model of osteoarthritic change where the cartilage has been enzymatically degraded with trypsin, the sodium NMR characteristics of the cartilage were determined as a function of changes in the proteoglycan content. The results demonstrate that the single quantum sodium signal decreases as the proteoglycan content of the cartilage matrix decreases. In addition, the relaxation characteristics of the sodium change such that the T1 is longer, the T2s is longer, and the T2f is shorter. Short echo-time, T1-weighted sodium images are presented which demonstrate that this information may be utilized to detect the loss of proteoglycans from articular cartilage.

Accurate 3' end processing and adenylation of human signal recognition particle RNA and alu RNA in vitro

Human signal recognition particle (SRP) RNA is transcribed by RNA polymerase III and terminates with -GUCUCUUUUOH on its 3' end. Our previous studies showed that the three terminal uridylic acid residues of human SRP RNA are post-transcriptionally removed and a single adenylic acid residue is added, resulting in a 3' end sequence of -GUCUCUAOH (Sinha, K. M., Gu, J., Chen, Y., and Reddy, R. (1998) J. Biol. Chem. 273, 6853-6859). In this study we show that the Alu RNA, corresponding to the 5' and 3' ends of SRP RNA, is also accurately processed and adenylated in vitro. Alu RNAs containing 7 or 11 additional nucleotides on the 3' end were accurately processed and then adenylated. Deletion analysis showed that an 87-nucleotide-long motif comprising of the 5' and 3' ends, including stem IV of the Alu RNA, is sufficient and necessary for the 3' end processing and adenylation. A 73-nucleotide-long construct with deletion of stem IV, required for the binding of SRP 9/14-kDa proteins, was neither processed nor adenylated. The adenylated Alu RNA as well as adenylated SRP RNA were bound to the SRP 9/14-kDa heterodimer and were immunoprecipitated by specific antibodies. A significant fraction of SRP RNA in the nucleoli was found to be processed and adenylated. These data are consistent with nascent SRP and/or Alu RNAs first binding to SRP 9/14-kDa protein heterodimer, followed by the removal of extra sequence on the 3' end and then the addition of one adenylic acid residue in the nucleus, before transport into the cytoplasm.

Stepwise transplantation of an active site loop between heat-labile enterotoxins LT-II and LT-I and characterization of the obtained hybrid toxins

Members of the cholera toxin family, including Escherichia coli heat-labile enterotoxins LT-I and LT-II, catalyze the covalent modification of intracellular proteins by transfer of ADP-ribose from NAD to a specific arginine of the target protein. The ADP-ribosylating activity of these toxins is located in the A-subunit, for which LT-I and LT-II share a 63% sequence identity. The flexible loop in LT-I, ranging from residue 47 to 56, closes over the active site cleft. Previous studies have shown that point mutations in this loop have dramatic effects on the activity of LT-I. Yet, in LT-II the sequence of the equivalent loop differs at four positions from LT-I. Therefore five mutants of the active site loop were created by a stepwise replacement of the loop sequence in LT-I with virtually all the corresponding residues in LT-II. Since we discovered that LT-II had no activity versus the artificial substrate diethylamino-benzylidine-aminoguanidine (DEABAG) while LT-I does, our active site mutants most likely probe the NAD binding, not the arginine binding region of the active site. The five hybrid toxins obtained (Q49A, F52N, V53T, Q49V/F52N and Q49V/F52N/V53T) show (i) great differences in holotoxin assembly efficiency; (ii) decreased cytotoxicity in Chinese hamster ovary cells; and (iii) increased in vitro enzymatic activity compared with wild type LT-I. Specifically, the three mutants containing the F52N substitution display a greater Vmax for NAD than wild type LT-I. The enzymatic activity of the V53T mutant is significantly higher than that of wild type LT-I. Apparently this subtle variation at position 53 is beneficial, in contrast to several other substitutions at position 53 which previously had been shown to be deleterious for activity. The most striking result of this study is that the active site loop of LT-I, despite great sensitivity for point mutations, can essentially be replaced by the active site loop of LT-II, yielding an active 'hybrid enzyme' as well as 'hybrid toxin'.

Effects of haloperidol on antioxidant defense system enzymes in schizophrenia

Dysregulation of free radical metabolism as reflected by abnormal erythrocyte activities of three critical enzymes of the antioxidant defense system (AODS), i.e. superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), has been reported in schizophrenic patients. The present study examined the effects of haloperidol, a standard antipsychotic agent, on the AODS enzymes, using a within-subject, repeated-measures, on-off haloperidol treatment design. The mean drug free period was 40 days. At baseline, there were no significant differences for all three enzymes between patients and age and sex-matched normal volunteers. During the drug-free condition, SOD activity, but not GSH-Px and CAT activities, was significantly higher relative to normal control subjects. However, within-subjects both SOD and GSH-Px activities, but not CAT activity, were higher in the drug-free condition compared to the treatment condition. No significant correlation was observed between SOD activity and plasma haloperidol (or daily haloperidol dose) levels. Smoking status, as assessed by the cotinine level, was unrelated to enzyme activities. In addition, none of the major AODS enzymes showed significant differences between relapsed and clinically stable patients. These findings suggest that haloperidol may not have direct regulatory effect on AODS enzyme activities and that SOD and GSH-Px activities may change in response to other factors such as change in symptom severity.

Laparoscopic cholecystectomy in cirrhotic patients

BACKGROUND

Reported mortality for open cholecystectomy in patients with cirrhosis ranges from 10% to 80%. Laparoscopic cholecystectomy has gained acceptance in the general population and has become the procedure of choice for symptomatic cholelithiasis. We reviewed our experience with the use of laparoscopic cholecystectomy in this group.

STUDY DESIGN

We did a retrospective review of the records of 25 consecutive laparoscopic choleoystectomy procedures performed on cirrhotic patients from May 1992 to July 1996.

RESULTS

There were no mortalities in our group. All procedures were completed laparoscopically. Mean length of stay was 1.7 days (range, 1 to 8 days). Morbidity consisted of wound hematomas, pneumonia, and ascites for a rate of 32%. Only patients with Child's Class A and Class B cirrhosis were operated on.

CONCLUSIONS

Laparoscopic cholecystectomy can be performed safely in cirrhotic patients with well compensated liver function.

In vivo expression of a variant human U6 RNA from a unique, internal promoter

We previously isolated a variant of the human U6 small nuclear RNA gene (87U6) and demonstrated that transcription of this gene is controlled by a novel internal promoter. It has now been shown that two blocks of sequence within the coding region are both necessary and sufficient to direct expression of 87U6 in transcription assays performed in vitro. In addition, 87U6 is expressed in vivo and can assemble into snRNP complexes. Specific primer extension assays on total RNA from HeLa cells shows that 87U6 RNA is present in these cells. Also, microinjection of plasmid encoded 87U6 genes into Xenopus laevis oocyte nuclei results in the expression of this variant RNA. Immunoprecipitation with anti-Sm antibodies suggests that 87U6 RNA assembles into a snRNP particle with U4 snRNA. Finally, the variant snRNA is capped with the U6 specific gamma-monomethyl phosphate cap when incubated in HeLa extracts. These data suggest that 87U6 RNA may function in the splicing process, in a manner similar to the wild-type U6 RNA. The recent observations of a minor class of mRNA introns that are spliced by a distinct collection of snRNP particles suggest an important role for variant snRNAs in the splicing of transcripts with alternative splice junctions.

Sodium multiple quantum spectroscopy of articular cartilage: effects of mechanical compression

The effects of mechanical compression on the multiple quantum coherences generated from sodium ions in articular cartilage were investigated. Cartilage samples obtained from bovine patellae were studied during compression at 0.7 MPa (100 psi) for 1 hour. The double quantum filtered spectra showed marked lineshape changes in the compressed samples. Compression did not seem to influence the lineshapes of the single quantum and triple quantum filtered spectra significantly. We found that the residual quadrupolar interaction was reduced in the compressed samples. Changes in the ordering of collagen fibers may be responsible for the observed effect.

Proton T1rho-dispersion imaging of rodent brain at 1.9 T

Detection of H2(17)O with proton T1rho-dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1rho dispersion of tissue. To investigate these properties, we implemented a T1rho imaging sequence on a 1.9-T Signa GE scanner. A series of T1rho images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5% (wt/vol) gelatin phantoms containing different concentrations of (17)O ranging from .037% (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1rho-dispersion in phantoms doped with H2(17)O, the T1rho of rat brain undergoes minimal dispersion for spin-locking frequencies between .2 and 1.5 kHz. A small degree of T1rho dispersion is present below .2 kHz, which we postulate arises from natural-abundance H2(17)O. Moreover, the signal-to-noise ratios of T1rho-weighted images are significantly better than comparable T2-weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1rho-dispersion imaging for detecting intravenous H2(17)O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.

Houseflies are an unlikely reservoir or vector for Helicobacter pylori

The route of transmission of Helicobacter pylori from individual to individual remains undefined. It has recently been reported that the domestic housefly, Musca domestica, when fed pure cultures of H. pylori, was able to harbor the organism in its midgut for up to 30 h (P. Grubel, S. Hoffman, F. K. Chong, N. A. Barstein, C. Mepani, and D. R. Cave, J. Clin. Microbiol. 35:1300-1303, 1997). Our investigation examined whether houseflies could acquire H. pylori from fresh human feces. Domestic houseflies (40 flies/group) were exposed for 24 h to feces from an H. pylori-positive volunteer, feces from an H. pylori-negative volunteer, or feces from an H. pylori-negative volunteer to which a known amount of viable H. pylori had been added. At various intervals, flies were sacrificed and the midguts were excised, homogenized, and plated in duplicate onto selective horse blood agar plates. All plates were incubated under microaerobic conditions at 37 degreesC for 14 days. Emergent colonies presumptive of H. pylori were picked and tested biochemically to confirm the identity as H. pylori. H. pylori was not recovered from houseflies fed human feces either naturally infected or artificially infected with H. pylori. These results suggest that the domestic housefly is not a vector for transmission or a reservoir for H. pylori infection.

Isolation and characterization of a new 110 kDa human nuclear RNA-binding protein (p110nrb)

RNA-protein interactions play key roles in many fundamental cellular processes such as RNA processing, RNA transport, and RNA translation. During our attempts to isolate the human U6 small nuclear RNA capping enzyme, we identified a new 110 kDa nuclear RNA-binding protein, designated p110nrb. The full-length cDNA clone for p110nrb was characterized, and it encodes a 963 amino acid polypeptide. It is a highly acidic protein (pI 5.28) and the carboxyl terminal portion contains two conserved RNP motifs. A databank search found a putative C. elegans protein that might be the p110nrb homologue. The p110nrb was overexpressed as a glutathione S-transferase fusion protein in insect Sf9 cells, purified by affinity chromatography and injected into rabbits to produce specific polyclonal antibodies. Immunofluorescent staining showed that p110nrb is distributed evenly throughout the nucleoplasm. Northern blots showed that the mRNA is expressed in all tissues examined. An in vitro RNA-binding assay showed that p110nrb bound to RNA. These data suggest that p110nrb may play a role in the metabolism of nuclear RNA.

Reduced level of plasma antioxidant uric acid in schizophrenia

There is evidence of dysregulation of the antioxidant defense system in schizophrenia. The purpose of the present study was to examine whether uric acid, a potent antioxidant, is reduced in the plasma of patients with schizophrenia. To this end, a within-subject, repeated measures, on-off-on haloperidol treatment design was utilized. Male schizophrenic patients with either a haloperidol treatment (n=47) or a drug-free condition (n=35) had significantly lower levels of plasma uric acid than the age- and sex-matched normal control subjects (n=34). Following haloperidol withdrawal, plasma uric acid levels were further reduced in schizophrenic patients (P=0.018; paired t-test, n=35). However, no relationship was found between uric acid levels and the length of the drug-free period (< 5 or > 5 weeks) or days drug free. In addition, the plasma levels of uric acid in patient groups were significantly and inversely correlated with psychosis. There was a trend for lower uric acid levels in relapsed patients relative to clinically stable patients. Smoking, which can modify plasma antioxidant capacity, was not found to have prominent effects on uric acid levels. The present finding of a significant decrease of a selective antioxidant provides additional support to the hypothesis that oxidative stress in schizophrenia may be due to a defect in the antioxidant defense system.

Reduced status of plasma total antioxidant capacity in schizophrenia

To examine whether antioxidant capacity is reduced in patients with schizophrenia, we determined plasma total antioxidant status (TAS) by quenching the absorbance of the radical cation formed by the reaction of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) with a metmyoglobin and hydrogen peroxide. TAS serves as an index of net antioxidant activity derived from various antioxidants in plasma. Male schizophrenic patients were compared with age- and sex-matched healthy control subjects, using a within-subject, repeated measures, on-off-on haloperidol treatment design. Drug-free patients were free of all psychotropic medications for an average of 32 days. Plasma TAS was significantly lower in patients with schizophrenia than in normal controls. Plasma TAS in patients was significantly and inversely correlated with symptom severity during the drug-free condition. There were no significant differences between on and off haloperidol-treatment conditions. When patients returned to haloperidol treatment after relapse, the plasma TAS remained fairly constant and was not significantly different from the same individuals during haloperidol-stabilization or drug-free periods. These findings are indicative of an impaired antioxidant defense system, not attributable to neuroleptic treatment, and lend further support to the notion that oxidative stress may have a pathophysiological role in schizophrenia.

MRI of hyperpolarized 3He gas in human paranasal sinuses

In this study, MRI of hyperpolarized 3He gas in human paranasal sinuses is presented. Helium images were obtained at 1.5 T, using a surface coil and a 2D, fast gradient-echo sequence with a nominal constant flip angle of 12 degrees. Coronal images of 20-mm thick slices were generated and compared with proton images of the corresponding sections. The images enable visualization of the paranasal sinuses and the nasal cavity, suggesting a potential use of this method not only in identifying the anatomical configuration of these pneumatic spaces, but also in assessing sinus ventilation.

Sodium MRI of human articular cartilage in vivo

Preliminary results from in vivo sodium MRI of human patellar articular cartilage are presented. Sodium images generated of an in vitro bovine patella clearly distinguish the region of proteoglycan depletion from the region of healthy cartilage. This provides the first evidence that sodium imaging may be used to detect changes due to osteoarthritis in vivo. The process of optimizing imaging time and signal-to-noise ratio, as well as potential implications in the detection of osteoarthritic change, are discussed.

The Splendore-Hoeppli phenomenon in hepatic botryomycosis

A 68 year old diabetic man developed septicaemia and multiple liver abscesses due to Streptococcus intermedius. Liver biopsy revealed streptococcal botryomycosis which showed the Splendore-Hoeppli phenomenon. Diabetes mellitus is an example of the immunosuppressed states that have been associated with botryomycosis.

Off-resonance proton T1rho dispersion imaging of 17O-enriched tissue phantoms

Proton T1rho dispersion imaging is a recently described method for indirect detection of 17O. However, clinical implementation of this technique is hindered by the requirement for a high-amplitude spin-locking field (gammaB1 > 1 kHz) that exceeds current limitations in specific absorption rate (SAR). Here, a strategy is offered for circumventing high SAR in T1rho dispersion imaging of 17O through the use of low-amplitude off-resonance spin-locking pulses (gammaB1 < 300 Hz). Proton spin-lattice relaxation times in the off-resonance rotating frame were measured in H2(17)O-enriched tissue phantoms. On- and off-resonance T1rho dispersion imaging was implemented at 2 T using a spin-locking preparatory pulse cluster appended to a standard spin-echo sequence. On- and off-resonance dispersion images exhibited similar 17O-based image contrast. Magnetization transfer effects did not depend on 17O concentration and had no effect on image contrast. In conclusion, off-resonance proton T1rho dispersion imaging shows promise as a safe, sensitive technique for generating 17O-based T1rho contrast without exceeding SAR limitations.

Adenylation of small RNAs in human cells. Development of a cell-free system for accurate adenylation on the 3'-end of human signal recognition particle RNA

The 3'-end sequences of several human small RNAs were determined, and the results show that a fraction of human cytoplasmic 7SL, ribosomal 5S, and nuclear U2, U6, and 7SK small RNAs contain a post-transcriptionally added adenylic acid residue on their 3'-ends. Incubation of HeLa cell extract in vitro in the presence of [alpha-32P]ATP resulted in labeling of several small RNAs including ribosomal 5S and cytoplasmic 7SL as well as U2 and U6 small nuclear RNAs. Analysis of 7SL RNA labeled in this in vitro adenylation system showed that a single adenylic acid residue is added to the 3'-end. These results show that the adenylation observed in the in vitro system reflects the post-transcriptional adenylation occurring in vivo.