Anticonvulsant effect of Uncaria rhynchophylla (Miq) Jack. in rats with kainic acid-induced epileptic seizure

This study investigated the anticonvulsant effect of Uncaria rhynchophylla (UR) and the physiological mechanisms of its action in rats. A total of 70 male Sprague-Dawley (SD) rats were selected for study. Thirty four of these rats were divided into 5 groups as follows: 1) CONTROL GROUP (n = 6): received intraperitoneal injection (i.p.) of kainic acid (KA, 12 mg/kg); 2) UR1000 group (n = 10), 3) UR500 group (n = 6) 4) UR250 group, received UR 1000, 500, 250 mg/kg i.p. 30 min prior to KA administration, respectively; 5) Contrast group: received carbamazepine 20 mg/kg i.p. 30 min prior to KA administration. Behavior and EEG were monitored from 15 min prior to drug administration to 3 hours after KA administration. The number of wet dog shakes were counted at 10 min intervals throughout the experimental course. The remaining 36 rats were used to measure the lipid peroxide level in the cerebral cortex one hour after KA administration. These rats were divided into 6 groups of 6 rats as follows: 1) Normal group: no treatment was given; 2) CONTROL GROUP: received KA (12 mg/kg) i.p.; 3) UR1000 group, 4) UR500 group, 5) UR250 group, received UR 1000, 500, 250 mg/kg i.p. 30 min prior to KA administration, respectively; 6) Contrast group: received carbamazepine 20 mg/kg i.p. 30 min prior to KA administration. Our results indicated that both UR 1000 and 500 mg/kg decreased the incidence of KA-induced wet dog shakes, no similar effect was observed in the UR 250 mg/kg and carbamazepine 20 mg/kg group. Treatment with UR 1000 mg/kg, 500 mg/kg, or 250 mg/kg and carbamazepine 20 mg/kg decreased KA-induced lipid peroxide level in the cerebral cortex and was dose-dependent. These findings suggest that the anticonvulsant effect of UR possibly results from its suppressive effect on lipid peroxidation in the brain.

Regression of orthotopic brain tumors by cytokine-assisted tumor vaccines primed in the brain

This study investigated the therapeutic effects of a rat glioma cell line, C6, that was engineered to secrete mouse GM-CSF (mGM-CSF) on intracerebral (i.c.) brain tumors. Significant antitumor immunity was induced in rats when the live or irradiated mGM-CSF-secreting tumor vaccine was implanted i.c. The antitumor activity was effective on small tumors and, to a lesser extent, on large tumors or tumors existing in vivo for a longer duration. Immunohistochemical analysis revealed cellular infiltrates (granulocytes, macrophages, and CD4+ and CD8+ T cells) at both the vaccine site and the tumor site, indicating that immune responses were similarly activated when tumor vaccine was inoculated in the brain, as at the subcutis. Additional studies demonstrated that the therapeutic effects of tumor vaccines on the large tumors or the long-existing tumors were enhanced by strategies such as increasing the dosage of tumor vaccines, using combined vaccines consisting of mGM-CSF and human interleukin-2, or combining tumor vaccine with herpes simplex virus thymidine kinase/ganciclovir treatment. All of the modified strategies yielded synergistic therapeutic effects on the large tumor burdens. The data presented herein suggest that cytokine gene therapy is highly promising for the treatment of i.c. gliomas.

Changes of pulse rate and skin temperature evoked by electroacupuncture stimulation with different frequency on both Zusanli acupoints in humans

The purpose of this study was to investigate the effect of electroacupuncture stimulation (EA) of different frequency on pulse rate and skin temperature. Sixteen healthy male medical student volunteers received EA of 2 Hz, and 100 Hz, respectively on the both Zusanli acupoints (St-36) while resting. Their pulse rates were measured on the middle finger, and skin temperature was taken between the thumb and index finger before, during, and after EA stimulation. Each test took 35 minutes. The initial 10 min were defined as baseline period (no EA), the following 15 min as the EA period and the last 10 min as the post-EA period. Three assessments were performed on each subject as follows: A) control assessment: no EA was done throughout the test; B) 2 Hz EA assessment: 2 Hz EA was applied to both Zusanli acupoints during the EA period; and C) 100 Hz EA assessment: 100 Hz EA was applied to both Zusanli acupoints during the EA period. Our results indicate that both 2 Hz EA and 100 Hz EA decreased pulse rates during the EA period, and these changes remained throughout the post-EA period in 2 Hz EA assessment, but not in 100 Hz EA assessment. Both 2 Hz and 100 Hz EA resulted in decreases of skin temperature during the EA period. Our conclusions are that 2 Hz EA and 100 Hz EA applied to both Zusanli acupoints resulted in the decrease of pulse rate, which possibly evoked greater parasympathetic nerve activity on heart beats. 2 Hz EA had a more sustained effect on heart beats than 100 Hz EA. Decreased skin temperatures in the EA period may have resulted from cutaneous vasoconstriction caused by EA induced sympathetic stress response, suggesting EA at least remains for 15 min in clinical application.

A cross-validation of the comprehensive assessment of activities of daily living after stroke

This study aimed to determine whether the Frenchay Activities Index and the Barthel Index assess different factors in stroke patients who survive for more than one year. The Frenchay Activities Index and the Barthel Index were administered via telephone interview. One hundred and twenty-four patients from the community participated in the study. All items of the Barthel Index and the Frenchay Activities Index, except reading books, were included in a factor analysis to determine the underlying constructs of the items. Four factors were found. One factor comprised all items from the Barthel Index and one item from the Frenchay Activities Index. The rest of the Frenchay Activities Index items loaded on three other factors. The combined scores, using simple transformation, had satisfactory distributions. The results support the hypothesis that the Frenchay Activities Index and the Barthel Index assess different factors in stroke patients who survive for more than one year. The Barthel Index score and the Frenchay Activities Index score could be combined to assess the entire range of activities of daily living functions in stroke.

Evidence that protein binding specifies sites of DNA demethylation

It has been hypothesized that protein factors may protect CpG islands from methyltransferase during development and that demethylation may involve protein-DNA interactions at demethylated sites. However, direct evidence has been lacking. In this study, demethylation at the EBNA-1 binding sites of the Epstein-Barr virus latent replication origin, oriP, was investigated by using human cells. Several novel findings are discussed. First, there are specific preferential demethylation sites within the oriP region. Second, the DNA sequence of oriP alone is not the target of an active demethylation process. Third, EBNA-1 binding is required for the site-specific demethylation in oriP. Interestingly, CpG sites adjacent to and between the EBNA-1 sites do not become demethylated. Fourth, demethylation of the first DNA strand in oriP at the EBNA-1 binding sites involves a passive (replication-dependent) mechanism. The second-strand demethylation appears to occur through an active mechanism. That is, EBNA-1 protein binding prevents the EBNA-1 binding sites from being remethylated after one round of DNA replication, and it appears that an active demethylase then demethylates these hemimethylated sites. This study provides clear evidence that protein binding specifies sites of DNA demethylation and provides insights into the sequence of steps and the mechanism of demethylation.

Cerebral cortex participation in the physiological mechanisms of acupuncture stimulation: a study by auditory endogenous potentials (P300)

Although acupuncture has traditionally used the acupoints formula to treat diseases, the physiological mechanisms involved and the effectiveness of therapy remain unclear. This study investigated the physiological mechanism(s) and response to acupuncture stimulation using the acupoints formula. Scalp-recorded potentials P300 were evoked by auditory stimulation of non-target and target in 13 normal adult volunteers. Latencies and amplitudes were measured. Three assessments were performed in each subject over a period of at least one week. Each assessment was divided into a control period with no acupuncture stimulation, followed by an acupuncture period and then a post-acupuncture period. Acupuncture needles were inserted into the body as follows: 1) non-acupoint: acupuncture needles were inserted 2 cm lateral to both Zusanli acupoints; 2) acupoint: acupuncture needles were inserted into both Zusanli acupoints; 3) acupoints formula: acupuncture needles were inserted into both Zusanli and Shousanli acupoints. Our results showed that both acupoint and acupoints formula assessments resulted in a significant decrease of P300 amplitudes during the acupuncture and post-acupuncture periods. However, there was significant difference in P300 amplitudes in the non-acupoint assessment during these periods. P300 changes in latencies and amplitudes were not significantly different between the acupoint assessment and the acupoints formula assessment. We concluded that acupuncture stimulation of both Zusanli acupoints resulted in a decrease of P300 amplitudes, suggesting the involvement of the cerebral cortex in sensory interaction when simultaneous sensations of the two types are received. No similar changes were observed in the non-acupoint assessment, which have been suggested to be related to so-called acupoint specificity. Results obtained using the acupoints formula were not significantly different from those using acupoints alone. These findings suggested that neuropsychological effects from stimulation of Zusanli acupoints and Shousanli acupoints are different.

Involvement of the 5' proximal coding sequences of hepatitis C virus with internal initiation of viral translation

The 5' nontranslated region (NTR) of hepatitis C virus (HCV) consists of 341 nucleotides (nt). This region comprises the majority of the internal ribosome entry site (IRES) which controls the efficiency of viral translation. Previous studies of the 3' boundary of the HCV IRES yielded conflicting data regarding the involvement of viral coding sequences in IRES activity. We therefore studied the functional significance of the 5' proximal coding sequences of the HCV core gene on IRES activity. We constructed monocistronic and bicistronic DNAs that contained either a chloramphenicol acetyl transferase (CAT) gene or a luciferase (Luc) gene as the reporter. Results from both in vitro and in vivo experiments indicated that the optimal IRES ranged within nt 1-371. Further mutational analyses of sequences surrounding the initiation codon revealed that primary sequences downstream of the AUG initiator rather than the secondary structure are important in regulating optimal IRES function. We are also able to demonstrate that a non-AUG codon could be used to initiate the synthesis of a reporter protein, albeit with lower efficiency. These findings bear important implications for the HCV IRES secondary structures.

Effects of the garlic components diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity in human colon tumour cells

Diallyl sulfide (DAS) and diallyl disulfide (DADS), major components of garlic, were used to determine inhibition of arylamine N-acetyltransferase (NAT) activity in a human colon tumour (adenocarcinoma) cell line. Two assay systems were performed, one with cellular cytosols (9000g supernatant), the other with intact bacterial cell suspensions. The NAT activity in a human colon tumour cell line was inhibited by DAS and DADS in a dose-dependent manner in both system: that is, the greater the concentration of DAS and DADS in the reaction, the greater the inhibition of NAT activities in both systems. The data also indicated that DAS and DADS decrease the apparent values of Km and Vmax of NAT enzymes from human colon tumour cells in both systems examined. This is the first report to demonstrate that garlic components do affect human colon tumour cell NAT activity.

Stochastic, stage-specific mechanisms account for the variegation of a human globin transgene

The random insertion of transgenes into the genomic DNA of mice usually leads to widely variable levels of expression in individual founder lines. To study the mechanisms that cause variegation, we designed a transgene that we expected to variegate, which consisted of a beta-globin locus control region 5' HS-2 linked in tandem to a tagged human beta-globin gene (into which a Lac-Z cassette had been inserted). All tested founder lines exhibited red blood cell-specific expression, but levels of expression varied >1000-fold from the lowest to the highest expressing line. Most of the variation in levels of expression appeared to reflect differences in the percentage of cells in the peripheral blood that expressed the transgene, which ranged from 0.3% in the lowest expressing line to 88% in the highest; the level of transgene expression per cell varied no more than 10-fold from the lowest to the highest expressing line. These differences in expression levels could not be explained by the location of transgene integration, by an effect of beta-galactosidase on red blood cell survival, by the half life of the beta-galactosidase enzyme or by the age of the animals. The progeny of all early erythroid progenitors (BFU-E colony-forming cells) exhibited the same propensity to variegate in methylcellulose-based cultures, suggesting that the decision to variegate occurs after the BFU-E stage of erythroid differentiation. Collectively, these data suggest that variegation in levels of transgene expression are due to local, integration site-dependent phenomena that alter the probability that a transgene will be expressed in an appropriate cell; however, these local effects have a minimal impact on the transgene's activity in the cells that initiate transcription.

Modulation of cerebral cortex in acupuncture stimulation: a study using sympathetic skin response and somatosensory evoked potentials

Although acupuncture has been widely used for treating disorders, its therapeutic mechanism remains unclear. In order to study the physiological mechanism of acupuncture stimulation, both palm recordings of sympathetic skin response (SSR) were evoked by electrical stimulation of the right median nerve on 13 normal adult volunteers. Median nerve evoked short-latency somatosensory evoked potential (SEPs) recordings were taken at least one week after SSR recording. The latencies and amplitudes were calculated. N13 component was obtained from Cv7, and N20 and P25 were from somatosensory cortex. The control did not receive acupuncture stimulation. Acupuncture needles were inserted into both Zusanli (St-36) acupoints as follows: 1) manual acupuncture (MA): using fingers to twist the acupuncture needle until so-called Der-Qi was obtained, 2) 2 Hz electroacupuncture (EA): 2 Hz square-wave electrical pulses were applied between the Zusanli needle and the Shangjuxu (St-37) needle bilaterally. Our results indicated that the mean latencies of SSR were largest during 2 Hz EA followed by MA stimulation, whereas the period of control exhibited the shortest mean latencies. In contrast, the mean amplitudes of SSR were smallest during the period of 2Hz EA, followed by the period of MA, and the period of control exhibited the largest mean amplitudes of SSR. The latencies of N13, N20 and P25 remained unchanged, but the amplitudes of P25 were largest during the period of 2Hz EA, followed by the period of MA; the period of control exhibited the smallest mean amplitudes of SEPs. The results suggest that acupuncture stimulation of both Zusanli acupoints inhibited SSR, which implies that the cerebral cortex contributed at least in part to this inhibition. The stimulation effect of 2Hz EA is stronger than MA.

Inter-rater reliability and validity of the action research arm test in stroke patients

BACKGROUND AND PURPOSE

The Action Research arm test (ARAT) was constructed for assessing recovery of upper extremity function after cortical injury. The objective of the study was to verify the inter-rater reliability and validity of the ARAT in stroke patients.

METHODS

50 stroke patients participated in the study. For the purpose of inter-rater study, the ARAT was administered by three experienced raters on each patient within a 3-day period. Validity was assessed by comparing the patients' scores on the ARAT with those obtained for the other well-validated measurements evaluating upper extremity motor impairment and disability.

RESULTS

Intra-class correlation coefficient (ICC) for the total score was 0.98 indicating very high inter-rater reliability. ICCs were also very high in each of the subscales. The score of the ARAT was closely correlated with that of the upper extremity part of the motor assessment scale, the arm sub-score of the motricity index and the upper extremity movements of the modified motor assessment chart (Pearson r = 0.96, 0.87 and 0.94, respectively).

CONCLUSION

The preliminary results of this study support the value of the ARAT for measuring recovery of arm-hand function in stroke patients.

V(D)J recombination activity in human hematopoietic cells: correlation with developmental stage and genome stability

V(D)J recombinase activity was measured in an array of human cell lines derived from hematopoietic malignancies representing various lineages and developmental stages. The level of recombinase activity was found to vary over a 2000-fold range between different cell lines. Several myeloid cell lines were positive for V(D)J recombinase activity, providing additional insight into the relationship between myeloid and lymphoid differentiation. Despite high levels of V(D)J recombination in two human acute lymphoblastic leukemia cell lines, the cytogenetic karyotype has remained essentially constant over several years of continuous cell culture. Silencing of recombination of chromosomal and minichromosomal targets has been strongly correlated with the replication of CpG methylated DNA in murine cells. Here, in human cells, we show that human minichromosomes bearing V(D)J recombination signals are protected well over 100-fold from recombination if they are CpG methylated, providing a rational basis for the karyotypic stability in cells with high levels of V(D)J recombination activity.

Regression of established mouse leukemia by GM-CSF-transduced tumor vaccine: implications for cytotoxic T lymphocyte responses and tumor burdens

This study investigated the therapeutic effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on a mouse leukemia model. By using a retroviral vector, mouse GM-CSF cDNA was transduced into a highly tumorigenic T leukemia cell line, RL male 1. Injection of GM-CSF-secreting RL male 1 cells into syngeneic BALB/c mice elicited protective immunity in the animals, which could regress preestablished tumors introduced either by a subcutaneous or in an intravenous route. However, the therapeutic effects were less prominent in the mice inoculated with a large tumor load or in mice treated later. Winn tests further demonstrated that the splenocytes from the late-treated group conferred poorer protective effects in terms of reducing the growth of parental RL male 1 cells in naive mice than the splenocytes from the early-treated group. Nonetheless, upon stimulation in vitro, the activity of tumor-specific cytotoxic T lymphocytes (CTL) was comparable in the splenocytes of both groups of mice. Histological analysis also indicated that the CD8+ T cells appeared as early as 3 days following vaccination at the vaccine sites and at the tumor sites in both groups of mice. Above observations implied that the T cells in the animals bearing large tumors appeared to be in a state of suppression or anergy. Systematic histological analyses for 2 weeks provided further insight into various infiltrates at the vaccine sites and at the tumor sites in response to the inoculation of GM-CSF-secreting tumor vaccine.

Stability of patch methylation and its impact in regions of transcriptional initiation and elongation

CpG DNA methylation has previously been correlated with the suppression of transcription. The mechanism of this suppression is not understood, and many aspects of the temporal and positional relationships between the region of methylation and transcription have not yet been defined. Here, 12-kb stable replicating episomes that can be maintained in human somatic cells for weeks to months were used. Such a system allows more direct manipulation and is free from the positional effects attendant with the analysis of endogenous loci or integrated transgenes. By using these circular minichromosomes, patches of CpG methylation were created to include or exclude the regions of transcriptional initiation and elongation. I found that a 0.5-kb patch of methylation that covered the promoter suppressed expression only 2-fold and that a 1.9-kb patch of methylation that covered the coding portion of the gene (but not the promoter) suppressed expression about 10-fold. In contrast, methylation of the entire minichromosome except for the promoter or the coding portion suppressed transcription about 50- to 200-fold. I infer the following. Methylation of the 0.5-kb promoter fragment does not significantly affect transcription at the level of transcription factor binding or local chromatin structure. The dominant effect on transcription occurs when the length of methylated DNA is long, with little disproportionate effect of methylation of specific regions, such as that of initiation or elongation. I also found that the boundaries between these methylated and unmethylated regions remained stable for the many weeks that I monitored them.

Antioxidant effects of dopamine and related compounds

The antioxidant and free radical scavenging effects of dopamine, noradrenaline, tyramine, and tyrosine were investigated and compared with alpha-tocopherol. The antioxidant effect of dopamine and its related compounds on peroxidation of linoleic acid were in the order of dopamine > alpha-tocopherol = tyramine > tyrosine > noradrenaline as measured by the thiocyanate method. These amine compounds had reducing power, and a scavenging effect on reactive oxygen species, i.e., superoxide anion and hydroxyl radical. The results for reducing power and scavenging effect of these amine compounds had a similar trend as their inhibition of linoleic acid peroxidation. The antioxidant activity of these amine compounds in soybean oil was also evaluated by the Rancimat method. The induction time to reach 100 meq/kg peroxide value (POV) of soybean oil for dopamine, alpha-tocopherol, tyramine, tyrosine, noradrenaline, and control were 9.0, 8.2, 8.0, 6.4, 4.6, and 4.3 h, respectively. The antioxidant efficacy of amine compounds seems to be correlated with the numbers of hydroxy groups and their position on the phenolic ring.

Factors influencing vocational outcomes following stroke in Taiwan: a medical centre-based study

This study was aimed at identifying the factors relating to return to work for stroke patients of working age in Taiwan, adjusting for confounding factors. A retrospective cohort study was used to test the association between patients' characteristics, such as medical condition at admission and sociodemographic factors, and the degree of return to work after stroke. Two hundred and forty-eight consecutive stroke survivors discharged from the National Taiwan University Hospital participated in the follow-up survey. Variables considered likely to influence return to work were collected from the patients' hospital records. Vocational outcomes were collected via questionnaire. Return to work was classified into four levels: (I) no return to work; (II) limited return to work; (III) partial return to work; and (IV) complete return to work. Of the 248 subjects surveyed, 105 (42.7%) subjects had not returned to work, 32 (12.9%) subjects had returned to work on a limited basis, 43 (17.3%) subjects had partially returned, and 68 (27.4%) subjects had returned to work completely. Cramer's V test and stepwise logistic regression were employed to examine factors influencing return to employment. Maximum weakness and employment institution were identified as the strongest predictors of return to work. In brief, nearly three-quarters of the patients did not resume their usual work roles after stroke. Maximum weakness and employment institution were the strongest predictors of return to work following a stroke in Taiwan.

Vitrectomy for endogenous Klebsiella pneumoniae endophthalmitis with massive subretinal abscess

A 39-year-old man with pyogenic liver abscess had bilateral endogenous Klebsiella pneumoniae endophthalmitis. At presentation, the left eye had a localized subretinal abscess. Despite repeated intravitreal amikacin and dexamethasone injections, a subretinal abscess spread and detached all of the retina. Pars plana vitrectomy with drainage of the subretinal abscess was performed. The retina was reattached, and the patient had 5/200 vision 5 months postoperatively. Early vitrectomy with drainage of the subretinal abscess may save some eyes with endogenous Klebsiella pneumoniae endophthalmitis.

Human gamma-aminobutyraldehyde dehydrogenase (ALDH9): cDNA sequence, genomic organization, polymorphism, chromosomal localization, and tissue expression

The cDNA and the gene (ALDH9) for a human aldehyde dehydrogenase isozyme, which has a high activity for oxidation of gamma-aminobutyraldehyde and other amino aldehydes, were cloned and characterized. The cDNA has an open reading frame of 1479 bp encoding 493 amino acid residues. The gene is about 45 kb and consists of 10 coding exons interrupted by nine introns. The gene was assigned to chromosome 1q22-q23, using fluorescence in situ hybridization. Northern blot hybridization indicated that the size of the mRNA is about 2.4 kb and that the gene is expressed at high levels in adult liver, skeletal muscle, and kidney and low levels in heart, pancreas, lung, and brain. The gene is polymorphic, i.e., C or T at nt 327 and C or G at nt 344.

Processing of branched DNA intermediates by a complex of human FEN-1 and PCNA

In eukaryotic cells, a 5' flap DNA endonuclease activity and a ds DNA 5'-exonuclease activity exist within a single enzyme called FEN-1 [flap endo-nuclease and 5(five)'-exo-nuclease]. This 42 kDa endo-/exonuclease, FEN-1, is highly homologous to human XP-G, Saccharomyces cerevisiae RAD2 and S.cerevisiae RTH1. These structure-specific nucleases recognize and cleave a branched DNA structure called a DNA flap, and its derivative called a pseudo Y-structure. FEN-1 is essential for lagging strand DNA synthesis in Okazaki fragment joining. FEN-1 also appears to be important in mismatch repair. Here we find that human PCNA, the processivity factor for eukaryotic polymerases, physically associates with human FEN-1 and stimulates its endonucleolytic activity at branched DNA structures and its exonucleolytic activity at nick and gap structures. Structural requirements for FEN-1 and PCNA loading provide an interesting picture of this stimulation. PCNA loads on to substrates at double-stranded DNA ends. In contrast, FEN-1 requires a free single-stranded 5' terminus and appears to load by tracking along the single-stranded DNA branch. These physical constraints define the range of DNA replication, recombination and repair processes in which this family of structure-specific nucleases participate. A model explaining the exonucleolytic activity of FEN-1 in terms of its endonucleolytic activity is proposed based on these observations.

A comparison of performance in added-purpose occupations and rote exercise for dynamic standing balance in persons with hemiplegia

OBJECTIVES

Adding purpose to daily occupations to promote performance is a basic premise of occupational therapy. This study investigated the hypothesis that in persons with hemiplegia, two added-purpose occupations would elicit more exercise repetitions than a rote exercise.

METHOD

In a counterbalanced order, 21 subjects with hemiplegia, aged 51 to 78 years, experienced all three conditions of a dynamic standing balance exercise that involved bending down, reaching, standing up, and extending the arm. One condition of added purpose involved the use of materials (small balls and target); a second added-purpose condition involved the subjects' imagination of the small balls. The third condition was the rote exercise without added purpose.

RESULTS

A one-way analysis of variance for related measures indicated that the subjects performed significantly differently in each of the three conditions (p < .001). A Tukey multiple comparison test revealed that the subjects did significantly more exercise repetitions in the added-materials condition and in the imagery-based condition than in the rote exercise condition (p < .05).

CONCLUSION

This study demonstrates how added purpose can enhance motor performance in persons with hemiplegia. Purpose may be effectively added to an exercise through the use of materials or imagery.

Improved gene expression by a modified bicistronic retroviral vector

We have previously described the construction of a bicistronic retroviral vector using the picornavirus internal ribosome entry site (IRES), which allows two genes expression simultaneously from a single transcript. This vector transcribes RNA efficiently; however, in some cases the levels of protein production are low. In this report, we further modified the bicistronic vector by abolishing the functional viral gag initiation codon that is retained in the vector at 5' to the first initiation codon of transduced gene. Five different genes, human interleukin 2 (hIL-2), human interleukin 4 (hIL-4), human granulocyte macrophage stimulating factor (hGM-CSF), herpes simplex virus thymidine kinase (HSV-tk) gene, and hepatitis C virus (HCV) core gene (C190), were tested on this modified vector for gene transfer and expression. Our results demonstrated that the new bicistronic vector greatly increased the protein levels when compared with the original one. As the RNA levels and splicing patterns from these two vectors remained similar, the improvement was most likely resulted from the increased translational efficiency.

The interaction of the somatosensory evoked potentials to simultaneous finger stimuli in the human central nervous system. A study using direct recordings

In order to investigate the interaction of sensory electrophysiologic fields arising from the adjacent second (II) and third (III) fingers and the distant second and fifth (V) fingers, direct recordings of somatosensory evoked potentials (SEPs) were performed from the sensory and motor cortices, the sensory thalamic nucleus (nucleus ventralis caudalis, VC) and the cuneate nucleus in humans during neurosurgical operations. Electrical stimulation was given to the II, III or V fingers individually, and also to pairs of either the II and III fingers or the II and V fingers simultaneously. The interaction ratio (IR) was devised as the ratio of amplitude attenuation caused by the simultaneous stimulation to two fingers compared with the amplitude of the arithmetically summed SEPs to the individual stimulation of two fingers. The IRs were calculated on N20 and P25 from the sensory cortex, P22 from the motor cortex, P17thal from the VC, and N16cune and P35cune from the cuneate nucleus. With both stimulations to the II and III fingers and the II and V fingers, P25 showed the greatest IR, followed by P22, then by P17thal, with N16cune exhibited the smallest IR. N20 and P35cune showed similar IRs and significantly greater IRs with II and III finger stimulation compared with II and V finger stimulation. These results thus indicate that the interaction of somatosensory impulses occurs in several structures along the sensory pathway in CNS, including the cuneate nucleus, the sensory thalamic nucleus, as well as sensory and motor cortices, with the greatest IRs in the cerebral cortices and the weakest ones in the brain-stem.(ABSTRACT TRUNCATED AT 250 WORDS)

Satellited 4q identified in amniotic fluid cells

Extra material was identified on the distal long arm of a chromosome 4 in an amniotic fluid specimen sampled at 16.6 weeks of gestational age. There was no visible loss of material from chromosome 4, and no evidence for a balanced rearrangement. The primary counseling issue in this case was advanced maternal age. Ultrasound findings were normal, and family history was unremarkable. The identical 4qs chromosome was observed in cells from a paternal peripheral blood specimen and appeared to be an unbalanced rearrangement. This extra material was NOR positive in lymphocytes from the father, but was negative in the fetal amniocytes. Father's relatives were studied to verify the familial origin of this anomaly. In situ hybridization with both exon and intron sequences of ribosomal DNA demonstrated that ribosomal DNA is present at the terminus of the 4qs chromosome in the fetus, father, and paternal grandmother. This satellited 4q might have been derived from a translocation event that resulted in very little or no loss from the 4q and no specific phenotype. This derivative chromosome 4 has been inherited through at least 3 generations of phenotypically normal individuals.

Sequence of human FEN-1, a structure-specific endonuclease, and chromosomal localization of the gene (FEN1) in mouse and human

We recently purified and cloned the gene for a DNA structure-specific endonuclease, FEN-1, from murine cells. The murine protein recognizes 5' DNA flap structures that have been proposed in DNA replication, repair, and recombination. Here, we report the sequence of the human FEN1 gene. The translated sequence is identical to peptide sequence obtained from maturation factor-1, which is 1 of the 10 essential proteins for cell-free DNA replication. The human protein has the same structure-specific DNA endonuclease activity as the murine protein. Two human chromosomal hybridization signals, 11q12 and 1p22.2, were observed by FISH analysis using human genomic clones homologous to the mouse Fen-1 gene. The localization on human 11q12 was confirmed using radiation-reduced hybrids. The mouse Fen-1 gene is assigned to chromosome 19 based on somatic cell hybrids. The significance of these FEN1 gene localizations in human and mouse is discussed.

Determination of lysine with ninhydrin-ferric reagent

Ninhydrin-ferric reagent reacts highly and specifically with lysine at a pH value of 1.0. Ferric ion inhibits the reaction of ninhydrin with proline, ornithine, glycine, arginine, and histidine. This method can be used to determine a lysine sample of high concentration without dilution. It has a linear response range from 0.0625 to 0.5 mg lysine.HCl.

Molecular cloning, genomic organization, and chromosomal localization of an additional human aldehyde dehydrogenase gene, ALDH6

Aldehyde dehydrogenase isozymes have been suggested to play a major role in the detoxification of aldehydes generated by alcohol metabolism and lipid peroxidation. We previously cloned and characterized four human nonallelic ALDH genes encoding different isozymes. The existence of an unique ALDH isozyme in human saliva and its polymorphism has been demonstrated previously. In this paper, we describe the cloning, characterization, and chromosomal mapping of an aldehyde dehydrogenase gene (ALDH6) expressed in the human salivary gland. The cloned ALDH6 cDNA is 3457 bp in length and contains an open reading frame encoding 512 amino acid residues. The deduced amino acid sequence showed that ALDH6 is larger than the human liver ALDH1 by 11 amino acid residues at the N-terminal, and the degree of identity between the two isozymes is 70% with an alignment of 500 amino acid residues. The human ALDH6 gene spans about 37 kb and consists of 13 exons. The putative TATA and CCAAT boxes and Sp1 binding sites are found in the 5' upstream region of the gene. Northern blot analysis demonstrated that the ALDH6 gene is expressed at low levels in many tissues and at higher levels in salivary gland, stomach, and kidney. The ALDH6 gene was assigned to chromosome 15q26 using fluorescence in situ hybridization.

Dependence of transcriptional repression on CpG methylation density

CpG methylation is known to suppress transcription. This repression is generally thought to be related to alterations of chromatin structure that are specified by the methylation. The nature of these chromatin alterations is unknown. Moreover, it has not been clear if the methylation repression occurs in an all-or-none fashion at some critical methylation density, or if intermediate densities of methylation can give intermediate levels of repression. Here I report a stable episomal system which recapitulates many dynamic features of methylation observed in the genome. I have determined the extent of transcriptional repression as a function of four densities of CpG methylation. I find that the repression is a graded but exponential function of the CpG methylation density such that low levels of methylation yield a 67 to 90% inhibition of gene expression. Higher levels of methylation extinguished gene expression completely. Transcription from methylated minichromosomes can be increased by butyrate treatment, suggesting that histone acetylation can reverse some of the repression specified by the methylated state. Sites of preferential demethylation occurred and may have resulted from transcription factor binding or DNA looping.

Terminal deletion of the long arm of chromosome 2 in a premature infant with karyotype: 46,XY,del(2)(q37)

We present a premature newborn boy with multiple congenital anomalies, including craniofacial anomalies, syndactyly, cardiac defects, and a horseshoe kidney associated with terminal deletion of 2q. The infant's karyotype was 46,XY,del(2)(q37). Clinical, cytogenetic, and autopsy findings are presented in this report. Clinical manifestations in this infant are compared with those four other known patients with terminal deletion of chromosome 2.

Structure and localization on the X chromosome of the gene coding for the human filopodial protein moesin (MSN)

Moesin is a member of a recently discovered family of closely related proteins that includes ezrin, radixin, and merlin. It is widely expressed in different tissues and cells and has been localized to filopodia and other membranous protrusions that are important for cell-cell recognition and signaling and cell movement. Here, we have localized the coding gene (MSN) to Xq11.2-q12 by Southern and Western blot analyses of Chinese hamster x human somatic cell hybrids and by fluorescence chromosomal in situ hybridization. Moesin-like sequences were identified on chromosomes 5 and 6. The murine Msn locus was mapped to the X chromosome as well by studying a rodent x mouse hybrid panel. The structure of the human moesin gene has been determined. The 12 exons are distributed over > 30 kb, and the exon/intron junctions demarcate individual highly conserved domains. Primer extension analysis revealed two major start transcription sites, 184 and 133 bp upstream of the initiation codon. The 5'-flanking region is GC-rich, lacks a TATA box, and contains four SP1 and one AP1 binding sites.

The human homolog of the glomerulosclerosis gene Mpv17: structure and genomic organization

Mice carrying a retroviral insert in both alleles of the Mpv17 gene develop glomerulosclerosis and nephrotic syndrome at young age. Thus, the Mpv17 gene is a recessive disease gene in mice and this mouse strain is a potential animal model for glomerular diseases in man. We here describe the isolation and analysis of a human homolog of this gene. By interspecies hybridisation cDNA clones representing a single RNA species were isolated from human liver. Sequence analysis revealed over 90% identify in a region coding for a protein of 176 amino acids and unknown function in both species. Cloning of the genomic locus revealed a single copy gene which we mapped to the short arm of chromosome 2 at band 2p23-p21. Determination of the intron-exon structure and the junction sequences enabled us to establish a PCR based procedure to isolate the coding region from human genomic DNA. Thus, it is now possible to analyse patients suffering from candidate diseases on the basis of a blood sample if biopsy material is not available.

V(D)J recombination in ataxia telangiectasia, Bloom's syndrome, and a DNA ligase I-associated immunodeficiency disorder

Ataxia telangiectasia (AT) and Bloom's syndrome (BS) patients are characterized by sensitivity to radiation, increased lymphoid malignancy, and frequent translocations to the antigen receptor loci. Because of these features, there has been a persistent question as to whether the V(D)J recombinase might be abnormal in cells from these patients. Such abnormalities might be due to inappropriate to inaccurate expression of components of the V(D)J recombinase or due to mutation in a component shared between V(D)J recombination and other cellular processes, such as DNA repair. Bloom's syndrome is associated with a ligation deficiency, and this activity may contribute in the end resolution steps of both site-specific and general DNA-processing reactions. In the current study, we have activated V(D)J recombination in normal, AT, and BS fibroblasts and in fibroblasts from a patient with mutations that largely abolish DNA ligase I activity. We find that the signal and coding joint formation of the V(D)J recombination reaction are entirely normal in AT, BS, and DNA ligase I mutant cells. In addition to ruling out abnormalities of the V(D)J recombinase in AT, BS, and DNA ligase I mutant cells, these studies suggest that DNA ligase I is unlikely to be required for signal or coding end joining in the V(D)J recombination reaction.

Somatic hypermutation of an immunoglobulin mu heavy chain transgene

We have analyzed somatic hypermutation of an immunoglobulin (Ig) heavy chain transgene. Hybridomas expressing the transgene were produced from immunized transgenic mice and transgene copies were sequenced to assay for mutation. In two IgM-producing hybridomas, as well as in several IgG-producing hybridomas, mutations were found in the VDJ region of the transgene. In the IgM-producing hybridomas, both mutated and unmutated transgene copies were present and expressed as mRNA. Several mutated transgene copies were present in a single cell and these showed different patterns of mutation. Two IgG-producing hybridomas isolated from a single animal also showed a hierarchical pattern of mutation indicating that transgene mutations can accumulate during B cell proliferation, similar to the mutational process for endogenous antibody genes. Among hybridomas that expressed both IgG and IgM molecules derived from the transgene, the isotype-switched gamma transgene copy exhibited a higher level of mutation than the mu transgene copies. Our results indicate that the 15-kb ARSmu transgene contains all the sequence information required to target the Ig-specific hypermutational machinery, and raise the possibility that sequences associated with the endogenous CH locus might enhance somatic mutation.

Serotonin receptor 1c gene assigned to X chromosome in human (band q24) and mouse (bands D-F4)

In the mammalian nervous system, serotonin (5-hydroxytryptamine) binds to distinct cell surface receptor subtypes that are defined by their ligand binding and effector-coupling properties. The 5HT1c receptor is a G-protein coupled receptor that stimulates phospholipase C-catalyzed hydrolysis of phosphatidylinositol bisphosphate, leading to the mobilization of intracellular calcium and to the activation of protein kinase C. By using somatic cell hybrid analysis and FISH, we have mapped the HTR1C locus to the human X chromosome, band q24 and to the mouse X chromosome region D-F4. Comparison of these map positions offers new insights into the evolution of human and murine X chromosomes. Since HTR1C is expressed in certain parts of the central nervous system and abnormal function of the serotoninergic system has been implicated in affective disorders, obsessive-compulsive disorder and epilepsy, establishing the precise map position of HTR1C is an important first step toward evaluating this locus as a candidate for mutations in these syndromes and in X-linked mental disorders.

Localization of the photoreceptor gene ROM1 to human chromosome 11 and mouse chromosome 19: sublocalization to human 11q13 between PGA and PYGM

Rom-1 is a retinal integral membrane protein that, together with the product of the human retinal degeneration slow gene (RDS), defines a photoreceptor-specific protein family. The gene for rom-1 (HGM symbol: ROM1) has been assigned to human chromosome 11 and mouse chromosome 19 by Southern blot analysis of somatic cell hybrid DNAs. ROM1 was regionally sublocalized to human 11p13-11q13 by using three mouse-human somatic cell hybrids; in situ hybridization refined the sublocalization to human 11q13. Analysis of somatic cell hybrids suggested that the most likely localization of ROM1 is in the approximately 2-cM interval between human PGA (human pepsinogen A) and PYGM (muscle glycogen phosphorylase). ROM1 appears to be a new member of a conserved syntenic group whose members include such genes as CD5, CD20, and OSBP (oxysterol-binding protein), on human chromosome 11 and mouse chromosome 19. Localization of the ROM1 gene will permit the examination of its linkage to hereditary retinopathies in man and mouse.

Analysis of the defect in DNA end joining in the murine scid mutation

Murine severe combined immune deficiency (scid) is marked by a 5,000-fold reduction in coding joint formation in V(D)J recombination of antigen receptors. Others have demonstrated a sensitivity to double-strand breaks generated by ionizing radiation and bleomycin. We were interested in establishing the extent of the defect in intramolecular and intermolecular DNA end joining in lymphoid and nonlymphoid cells from scid mice. We conducted a series of studies probing the ability of these cells to resolve free ends of linear DNA molecules having various biochemical end configurations. We find that the stable integration of linear DNA into scid fibroblasts is reduced 11- to 75-fold compared with that in normal fibroblasts. In contrast, intramolecular and intermolecular end joining occur at normal frequencies in scid lymphocytes and fibroblasts. This normal level of end joining is observed regardless of the type of overhang and regardless of the requirement for nucleolytic activities prior to ligation. The fact that free ends having a wide variety of end configurations are recircularized normally in scid cells rules out certain models for the defect in scid. We discuss the types of DNA end joining reactions that are and are not affected in this double-strand break repair defect in the context of a hairpin model for V(D)J recombination.

Tissue-specific expression and chromosome assignment of genes specifying two isoforms of subunit VIIa of human cytochrome c oxidase

Subunit VIIa of mammalian cytochrome c oxidase (COX; EC 1.9.3.1) exists in at least two isoforms, one present in all tissue types ('liver' isoform; COX VIIa-L) and the other specific for cardiac and skeletal muscle (COX VIIa-M). We have isolated a full-length cDNA encoding human COX VIIa-M. The deduced polypeptide represents the human ortholog of COX VIIa-M, as it shares 78% identity with bovine COX VIIa-M, but only 63% identity with human COX VIIa-L. Northern-blot analysis of primate tissues demonstrated that COXVIIa-M mRNA is present only in muscle tissues; in contrast, the COXVIIa-L mRNA is present in both muscle and nonmuscle tissues. Southern-blot hybridization of human-rodent cell hybrid genomic DNA indicates that the COXVIIa-M gene maps to a single locus on chromosome 19, designated COX7AM. In contrast, COXVIIa-L cDNA probes hybridized to fragments from two COX7AL loci, on chromosomes 4 and 14.

Mitochondrial and nuclear variants in a U.S. black population: origins of a hybrid population

The maternal transmission of mitochondria in higher eukaryotes makes it possible to distinguish between reciprocal matings, since offspring possess the mitochondrial DNA variants received from the mother. This possibility can be extended to hybrid populations, the mitochondrial frequencies reflecting the relative maternal contributions from the parental populations. Nuclear variations reflect the relative genetic contributions of the parental populations, irrespective of parental sex. The U.S. Black population is a hybrid of West African and European populations. The African-European matings that contributed to the present Black population are traditionally considered to have been almost exclusively between African females and European males. We have studied nuclear and mitochondrial variants in a sample of U.S. Blacks, comparing them with published frequencies from African and Caucasian groups. Our results suggest that the mitochondria of present-day American Blacks are derived from Caucasians to an extent similar to nuclear genes. In contrast to traditional beliefs, the contribution from Caucasian females is of the same magnitude as that from Caucasian males.

V(D)J recombination on minichromosomes is not affected by transcription

It has been shown previously by others that transcription is temporally correlated with the onset of V(D)J recombination at the endogenous antigen receptor loci. We have been interested in determining whether this temporal correlation indicates a causal connection between these two processes. We have compared V(D)J recombination minichromosome substrates that have transcripts running through the recombination zone with substrates that do not in a transient transfection assay. In this system, the substrates acquire a minichromosome conformation within the first several hours after transfection. We find that the substrates recombine equally well over a 100-fold range in transcriptional variation. In additional studies, we have taken substrates that have low levels of transcription and inhibited transcription further by methylating the substrate DNA or by treating the cells with a general transcription inhibitor (alpha-amanitin). Although these treatments decrease the level of expression an additional 10-100-fold, there is still no observable effect on V(D)J recombination. Based on these results, we conclude that transcription is not necessary for the V(D)J reaction mechanism and does not alter substrate structure at the DNA level or at the simplest levels of chromatin structure in a way that affects the reaction.

Transient immunoglobulin M antibody response to hepatitis C virus capsid antigen in posttransfusion hepatitis C: putative serological marker for acute viral infection

The development of serological assays for hepatitis C virus (HCV) has made specific diagnosis possible. However, markers useful in indicating acute-phase HCV infection have not been identified. By an immunoblotting method, we characterized the IgM and IgG antibody response against HCV capsid antigen in patients with HCV infection. Among 88% of patients with acute posttransfusion hepatitis C recruited in a prospective study, there was a transient IgM antibody response. The IgM antibody appeared shortly after onset of hepatitis (average 3.7 weeks), persisted for several months (average 18 weeks), and then disappeared. In contrast, the IgG antibody persisted long-term once it appeared. Among patients with chronic hepatitis C with milder disease activities (serum aminotransferase increase above normal levels of less than 4-fold), the IgM antibody was negative in the majority (72%). In those with acute exacerbations (aminotransferase increase of greater than 10-fold), about 55% were negative for the IgM antibody. The reactivity of the IgM antibody in the rest was weaker or became negative upon further dilution of serum. The results suggest that IgM anti-capsid antibody may serve as a marker indicating acute or active HCV infection.

Improved gene expression by a U3-based retroviral vector

To improve the expression of the genes transduced by retroviral vectors, we have constructed a U3-based retroviral vector and evaluated its effect on the expression of an insert from the internal promoter. The unique feature of the vector is that the transduced gene is inserted at the U3 region of the 3' long terminal repeats (LTR). Consequently, in the infected cells the gene is duplicated and transferred to the 5'-LTR. When compared with the conventional retroviral vectors which insert the gene within the retroviral transcriptional unit, the U3-based vectors greatly enhanced the expression of the transduced gene under all three promoters tested, viz. the cytomegalovirus immediately early gene promoter (CMV), the SV40 early gene promoter (SV), and the herpes simplex virus thymidine kinase gene promoter (TK). The SV and TK promoters which were previously shown suppressed by the retroviral promoter in the conventional construction restored their potencies in the U3-based vectors. Our results therefore suggested that the U3-based vectors are more advantageous than the conventional vectors for gene expression.

CpG methylated minichromosomes become inaccessible for V(D)J recombination after undergoing replication

The physical parameters controlling the accessibility of antigen receptor loci to the V(D)J recombination activity are unknown. We have used minichromosome substrates to study the role that CpG methylation might play in controlling V(D)J recombination site accessibility. We find that CpG methylation decreases the V(D)J recombination of these substrates more than 100-fold. The decrease correlates with a considerable increase in resistance to endonuclease digestion of the methylated minichromosome DNA. The minichromosomes acquire resistance to both the intracellular V(D)J recombinase and exogenous endonuclease only after DNA replication. Therefore, CpG methylation specifies a chromatin structure that, upon DNA replication, is resistant to eukaryotic site-specific recombination. These findings are important to V(D)J recombination as well as to the chromatin assembly of methylated DNA during replication.

Induced reciprocal translocation in transgenic mice near sites of transgene integration

Transgenic mice (JCP0 #18), heterozygous for an insertion of approximately 50 copies of the rat peripheral myelin (P0) protein cDNA, displayed a pattern of reduced litter size that suggested a chromosome rearrangement. Chromosome banding studies of fetal cells disclosed the presence of an apparently balanced translocation between a Chromosome (Chr) 1 and 14 with breakpoints at bands 1H3 and 14C3. In situ hybridization of biotin-labeled P0 rat cDNA probe to chromosome spreads and detection of specific signal with fluorescein isothiocyanate-conjugated avidin revealed a strong signal on the 1(14) translocation chromosome at the site of the breakpoint. A weaker signal was present near the breakpoint on the 14(1) derivative chromosome. These results suggest an etiologic relationship between the insertion of the transgene and the origin of the translocation. To further elucidate possible mechanisms, we first mapped the endogenous P0 gene (gene symbol Mpp). As previously reported (You et al., Genomics 9: 751, 1991), we found that Mpp is located on Chr 1 in the region of the translocation breakpoint in JCP0 mice. Subsequently, we have carried out pulsed-field gel and standard Southern analyses with P0 gene probes, but found no evidence for a direct involvement of the endogenous P0 gene in the process that generated the balanced reciprocal translocation. Thus, we favor the hypothesis that, during repair of DNA strand breakage--possibly induced by the microinjection procedure--the transgene copies were ligated to broken ends of Chrs 1 and 14. According to convention, this translocation is designated T(1;14)1Po. Homozygotes are phenotypically normal and breed well; they will be useful for genetic and physical mapping of Chrs 1 and 14.

Characterization and chromosomal mapping of a human steroid 5 alpha-reductase gene and pseudogene and mapping of the mouse homologue

The enzyme steroid 5 alpha-reductase catalyzes the conversion of testosterone into the more powerful androgen, dihydrotestosterone. We previously described the cloning of rat and human cDNAs that encode steroid 5 alpha-reductase and their expression in oocytes and cultured cells. Here, we report the isolation, characterization, and chromosomal mapping of two human steroid 5 alpha-reductase genes. One gene (symbol SRD5A1) is functional, contains five exons separated by four introns, and maps to the distal short arm of chromosome 5. Two informative restriction fragment length polymorphisms are present in exons 1 and 2 of this gene. A second gene (symbol SRD5AP1) has all of the hallmarks of a processed pseudogene and was mapped to the q24-qter region of the X chromosome. In the mouse, a single steroid 5 alpha-reductase gene (Srd5 alpha-1) is linked to Xmv-13 on chromosome 13.

Genomic organization and chromosomal localization of the TAPA-1 gene

TAPA-1 is a 26-kDa integral membrane protein expressed on many human cell types. Antibodies against TAPA-1 induce homotypic aggregation of cells and can inhibit their growth. The murine homologue of TAPA-1 was cloned from both cDNA and genomic DNA libraries. A very high level of homology was found between human and mouse TAPA-1. The 5' untranslated region of the TAPA-1 gene resembles housekeeping gene promoters with respect to G + C content and the presence of potential Sp1 binding sites. The chromosomal localization of human and murine TAPA-1 genes was determined by Southern blot experiments using DNA from somatic cell hybrids. The genes were found to be part of a conserved syntenic group in mouse chromosome 7 and the short arm of human chromosome 11. The organization of the TAPA-1 gene and the projection of the exon boundaries on the proposed protein structure are presented.

Genomic organization and chromosomal localization of the TAPA-1 gene

TAPA-1 is a 26-kDa integral membrane protein expressed on many human cell types. Antibodies against TAPA-1 induce homotypic aggregation of cells and can inhibit their growth. The murine homologue of TAPA-1 was cloned from both cDNA and genomic DNA libraries. A very high level of homology was found between human and mouse TAPA-1. The 5' untranslated region of the TAPA-1 gene resembles housekeeping gene promoters with respect to G + C content and the presence of potential Sp1 binding sites. The chromosomal localization of human and murine TAPA-1 genes was determined by Southern blot experiments using DNA from somatic cell hybrids. The genes were found to be part of a conserved syntenic group in mouse chromosome 7 and the short arm of human chromosome 11. The organization of the TAPA-1 gene and the projection of the exon boundaries on the proposed protein structure are presented.

V(D)J recombination: evidence that a replicative mechanism is not required

We examined a series of extrachromosomal DNA substrates for V(D)J recombination under replicating and nonreplicating conditions. Complete and partial replications were examined by monitoring the loss of prokaryote-specific adenine methylation at 14 to 22 MboI-DpnI restriction sites (GATC) on the substrates. Some of these sites are within 2 bases of the signal sequence ends. We found that neither coding joint nor signal joint formation requires substrate replication. After ruling out replication as a substrate requirement, we determined whether replication had any effect on the efficiency of V(D)J recombination. Quantitation of V(D)J recombination efficiency on nonreplicating substrates requires some method of monitoring the entry of substrate molecules into the cells. We devised such a method by monitoring DNA repair of substrates into which we had substituted deoxyuridine for 10 to 20% of the thymidine nucleotides in the DNA. The substrates which enter the lymphoid cells were repaired efficiently in vivo by the eukaryotic uracil DNA repair system. Upon plasmid harvest, we distinguished repaired (entered) from unrepaired (not entered) plasmids by cleaving unrepaired molecules with uracil DNA glycoylase and Escherichia coli endonuclease IV in vitro. This method of monitoring DNA entry does not appear to underestimate or overestimate the amount of DNA entry. By using this method, we found no significant quantitative effect of DNA replication on V(D)J recombination efficiency.