Dysgerminoma of the ovary with hypercalcemia associated with elevated parathyroid hormone-related protein

The purpose of the present paper is to present a rare case of dysgerminoma of the ovary with hypercalcemia showing elevation of multiple serum tumor markers including parathyroid hormone-related protein (PTH-rP). An 18-year-old unmarried woman, with ovarian dysgerminoma showing hypercalcemia and elevated serum PTH-rP, received six courses of a combination chemotherapy consisting of bleomycin, etoposide and cisplatin after her first surgery, and had no evidence of recurrence approximately 30 months after completing the chemotherapy.

Different behavior of forearm blood flow during intermittent isometric handgrip in a thermo-neutral and a hot environment

The purpose of the present study was to evaluate the different behavior of forearm blood flow (FBF) during intermittent isometric handgrip (IIHG, 6 seconds contraction +6 seconds relaxation) in a thermoneutral versus a hot environment. Six healthy men performed three times of 5-minute period IIHG at three different work loads (10%, 20% and 30% MVC). The IIHG was performed with the right hand. The experiments of IIHG were performed at two different air temperatures (25 degrees C and 40 degrees C, RH: 50%), and an experiment without work was also carried out at 40 degrees C (RH: 50%). The physiological responses measured involved heart rate (HR), cardiac output (CO), mean arterial blood pressure (MBP), FBF, and skin blood flow (SBF). HR, CO and SBF showed higher values during IIHG at 40 degrees C than at 25 degrees C. MBP had a tendency to increase with the intensity of work load at both 25 degrees C and 40 degrees C. Since intramuscular pressure might increase during contraction periods at 20% MVC and 30% MVC at 25 degrees C, FBF was significantly higher during relaxation periods than during contraction periods. FBF showed similar values between contraction and relaxation periods at 10% MVC at both temperatures. The present study suggested that FBF was sufficient for active muscles during IIHG at 10% MVC. FBF of contraction periods was close to that of relaxation periods at 40 degrees C due to the modulation of the sympathetic outflow to the muscles and/or the decreased efficiency of the muscle pump. It was suggested that FBF showed different behaviors during HHG at 25 degrees C versus at 40 degrees C.

Effects of cisapride on gallbladder emptying and pancreatic polypeptide and cholecystokinin release in humans

We investigated the effects of cisapride on gallbladder motility and on the release of pancreatic polypeptide and cholecystokinin in the fasting and postprandial states. Cisapride (7.5 mg) and/or a test meal was administered intraduodenally to seven healthy volunteers with or without atropine pretreatment (0.5 mg, i.m.). In the fasting state, cisapride increased gallbladder volume to 154% of the basal level, and significantly elevated plasma pancreatic polypeptide levels. The effects of cisapride were inhibited by atropine. In the postprandial state, integrated pancreatic polypeptide and cholecystokinin responses were increased by cisapride to 180% and 192%, respectively, of control values. Atropine inhibited the integrated gallbladder and pancreatic polypeptide response to about 60% of the control value, but did not affect the cholecystokinin response. These observations suggest that: (1) fasting gallbladder tone is influenced by cholinergic inhibitory mechanisms, (2) acetylcholine (ACh) is the final mediator for about 40% of the postprandial gallbladder emptying and pancreatic polypeptide response, and (3) coordination between the ACh-independent cholecystokinin response and ACh-dependent pancreatic polypeptide response may be important in the regulation of postprandial gallbladder emptying.

Diverse incidences of individual oligopeptides (dipeptidic to hexapeptidic) in proteins of human, bakers' yeast, and Escherichia coli origin registered in the Swiss-Prot data base

Oligopeptidic permutations of the 20 amino acid residues give rise to proteins of diverse functions. Our long-term goal is to produce a lexicon of oligopeptides, classifying them into at least five categories: (i) ubiquitous, (ii) function specific, (iii) group specific, (iv) species specific, and (v) nonexistent. To begin with, we report on the varying frequencies of individual oligopeptides (dipeptidic to hexapeptidic in length) found among 2862 human proteins, 1942 Saccharomyces cerevisiae proteins, and 2672 Escherichia coli proteins registered in the Swiss-Prot data base (version 29.0, released in June 1994). At all lengths (dipeptides to hexapeptides), homooligopeptides were very prominent among the most frequently occurring varieties in proteins of human and bakers' yeast origins. However, this was not the case with E. coli. While all of the expected 20(3) varieties of tripeptides were found among human proteins, three tripeptides (Cys-Cys-Trp, Trp-Trp-Cys, and Trp-Trp-His) were missing from the bakers' yeast proteins. Three tripeptides (Cys-Ile-Trp, Cys-Met-Tyr, and Cys-Trp-Trp) were also absent from E. coli proteins. Inasmuch as the Swiss-Prot data base already contained 67% of the expected total of 4000 E. coli proteins, it is virtually certain that 96,000 varieties of hexapeptides containing at least one or another of the three missing tripeptides noted above shall be nonexistent in E. coli. Furthermore, the observation of missing tripeptides in the bakers' yeast proteins suggests that nonexistent hexapeptides shall be highly phylum specific. Because of the sample size, only a small fraction of the 20(6) varieties of hexapeptides were expected to be encountered in the present survey. Indeed, only 1.2-1.5% of the possible hexapeptides were found, and the average copy number of observed hexapeptides varied between 1.06 and 1.25. Nevertheless, 33 varieties of hexapeptides occurred in 102-169 copies among human proteins. Furthermore, 15 of the 33 varieties contained such rarely used residues as Tyr, His, Cys, and Trp.

Possible function of Ah receptor nuclear translocator (Arnt) homodimer in transcriptional regulation

Arnt (Ah receptor nuclear translocator) is a member of a transcription factor family having characteristic motifs designated bHLH (basic helix-loop-helix) and PAS and was originally found as a factor forming a complex with Ah receptor (AhR) to bind the specific xenobiotic responsive element (XRE) sequence for induction of drug-metabolizing P4501A1. We have examined interaction of Arnt with other PAS proteins--Drosophila Per, Sim, and AhR--by the coimmunoprecipitation method. Arnt formed a homodimer with itself as well as heterodimers with the others by means of the PAS and HLH domains in a cooperative way. The Arnt homodimer binds the sequence of adenovirus major late promoter (MLP) with the E box core sequence CACGTG, suggesting that the CAC half of the XRE, CACGCN(A/T), recognized by the AhR-Arnt heterodimer is a target for Arnt. Cotransfection experiments using CV-1 cells with an Arnt expression plasmid and a MLP chloramphenicol acetyltransferase (CAT) reporter plasmid revealed that Arnt markedly activated CAT expression, indicative of a newly discovered regulatory role of Arnt.

Early detection of Knudson's two-hits in preneoplastic renal cells of the Eker rat model by the laser microdissection procedure

Hereditary renal cell carcinomas invariably develop by the age of 1 year in Eker rats. At the histological level, renal cell carcinomas develop through multiple stages from early preneoplastic lesions (e.g., phenotypically altered tubules) to adenomas. We previously reported that ionizing radiation induces additional tumors (large adenomas and carcinomas) in a linear dose-response relationship and that loss of heterozygosity (LOH) at chromosome 10, where the predisposing tuberous sclerosis (Tsc2) gene is localized, was found in the renal cell carcinomas which developed from hybrid F1 rats carrying the Eker mutation, indicating that in heterozygotes two events (one inherited, one somatic) are necessary to produce at least large adenomas and carcinomas. This study was designed to examine LOH in the earliest preneoplastic lesions, using a laser microdissection procedure. We could accurately dissect single altered renal tubules out of freeze-dried sections and clearly detected LOH in 4 of 19 altered tubules (21%). This is the first demonstration of LOH in single renal tubules. Our present results support the theory of a second, somatic mutation (second hit) as rate-limiting step of renal carcinogenesis in the Eker rat model of dominantly inherited cancer and the tumor suppressor nature of the Tsc2 gene function.

Problems of neuroblastoma screening for 6 month olds and results of second screening for 18 month olds

Nationwide neuroblastoma mass screening for 6-month-old infants (first screening) was introduced in Japan in 1985. About 110 neuroblastoma cases are detected annually by the first screening and treated, with a survival rate of 97%. Sensitivity of the first screening (positive cases/positive cases+false negative cases) is about 75%, and the prognosis of false-negative cases is unfavorable. A second screening at 18 months of age was started to rescue false-negative cases in Miyagi Prefecture in May 1992. Of 62 neuroblastoma cases treated in our hospital since 1985, 40 cases had received the first screening. Twenty cases were positive at first screening, 18 cases were false negative, and 2 cases were false negative and picked up by the second screening. Age distribution of false-negative cases ranged from 12 to 83 months and included 12 cases younger than 36 months old. Only 5 of 18 false-negative cases are alive without the disease. From May 1992 to November 1993, 14,282 infants had received the second screening (compliance rate: about 75%), and 2 neuroblastoma cases were detected. The first case was stage III with paraortic lymph node metastases, Shimada UH, aneuploidy and negative N-myc amplification. The second case was stage II with Shimada FH, aneuploidy, and negative N-myc amplification. Both cases are alive now without the disease after undergoing radical operation and chemotherapy. The first screening is effective for early detection of neuroblastoma cases, but the sensitivity is insufficient; the authors recommend a second screening to rescue false-negative cases.

Cardiac pacing in fetal lambs: intrauterine transvenous cardiac pacing for fetal complete heart block

To evaluate the feasibility of intrauterine transvenous cardiac pacing, the right ventricular output was measured during pacing in six fetal lambs. Under maternal anesthesia, the uterus was opened, and, under local anesthesia, the pacing lead (Medtronic Capsure SP4023) was inserted via the fetal left internal jugular vein. Right ventricular output was estimated using an Aloka SSD-730 ultrasound device, and tricuspid valve regurgitation was evaluated with an Aloka SSD-880 using the transuterine approach. The ultrasonic right ventricular cardiac output was measured under three different conditions: (1) with the tip of the pacing lead in the superior vena cava (control); (2) with the tip of the pacing lead in the right ventricle; and (3) with pacing at 200 beats/min. The right ventricular output decreased when the pacing lead was inserted into the right ventricle, as well as during pacing at 200 beats/min ([1] = 107 +/- 13.2 mL/kg per min; [2] = 73.8 +/- 17.5 mL/kg per min; and [3] = 78.3 +/- 23.6 mL/kg per min). Tricuspid regurgitation did not change under any of the conditions tested. Intrauterine transvenous cardiac pacing was successfully achieved. Insertion of the pacing lead into the right ventricle decreased the ventricular output without increasing tricuspid valve regurgitation.

Hairpin ribozyme-mediated cleavage of the full-length beta-glucuronidase (GUS) mRNA

We designed three hairpin ribozymes to cleave Escherichia coli beta-glucuronidase (GUS) mRNA and tested those activities in vitro. One of the ribozymes was designed to form 9 base pairs in total with the target GUS mRNA, and the other two ribozymes had longer substrate binding sites. All ribozymes cleaved the model substrate (100 bases long) at the predicted target site. Two ribozymes containing longer substrate binding sites cleaved the substrate much more efficiently than the other ribozyme containing shorter substrate binding site. Also, the ribozymes with long substrate binding sites had high activity against the full-length GUS mRNA (1.9 kilobases) and maintained the activity even at a low temperature, 26 degrees C, a general growth condition of plant cells. Effects of the substrate binding site length of the ribozyme on cleavage activity are discussed.

Sleep disturbance in elderly patients with cognitive impairment, decreased daily activity and periventricular white matter lesions

We investigated how sleep disturbance is correlated with brain lesions, cognitive impairment and decreased daily activity (ADL). Two hundred and four chronically ill patients including patients with vascular dementia were classified into eight groups based on cognitive function, ADL and grades of PVL (periventricular lucency) as shown by computerized tomography. Visual monitoring of the sleep/wake state was performed hourly for 14 consecutive days and the daytime sleep hours and the nighttime sleep hours were determined based on detected disturbances in the sleep/wake pattern. Whether any specific infarcted regions were correlated with sleep disturbance was also evaluated. We found that daytime sleep hours were increased and nighttime sleep hours were decreased by three single factors: cognitive impairment, decreased ADL and the severe grade of PVL. As for an interactive effect of the two factors, daytime sleep hours were increased by dementia with decreased ADL (independent of PVL) and increased by decreased ADL with the severe grade of PVL (independent of dementia). Although three factors affected sleep independently, ADL has an interactive effect on sleep with dementia and with PVL. No specific cortical regions related to sleep disturbance were found.

Hypoglossal nerve stimulation affects the pressure-volume behavior of the upper airway

To determine the effects of electrical hypoglossal nerve and submental stimulation on upper airway collapsibility, we examined the pressure-volume (P-V) relationships during bilateral supramaximal stimulation of the distal cut hypoglossal nerve ends over a range of frequencies from zero to 100 Hz in the sealed upper airway of 10 anesthetized supine dogs. Animals were artificially ventilated with 50% O2 and maintained under relative hyperoxia and hypocapnia during the study to eliminate the ventilatory drive output. Sealed upper airway pressures were obtained during random injections of different volumes of air from zero to 50 ml with and without hypoglossal nerve stimulation, and the upper airway P-V curves were obtained. The characteristics of the P-V curves were as follows: (1) the upper airway compliance defined as the slope of the regression of P-V curves fell from 4.07 +/- 0.33 ml/cm H2O without stimulation to 3.02 +/- 0.30 ml/cm H2O with stimulation at 50 Hz and plateaued at frequencies greater than 50 Hz, and (2) the volume at a given pressure during stimulation was larger than that without stimulation. The effects of submental stimulation on upper airway collapsibility were similar to those of hypoglossal nerve stimulation. These results suggest that the increase of upper airway muscle tone by hypoglossal nerve or submental stimulation stiffens the upper airway and that increases in muscle tone expand the upper airway.

The SMS1 gene encoding a serine-rich transmembrane protein suppresses the temperature sensitivity of the htr1 disruptant in Saccharomyces cerevisiae

A new gene (SMS1; serine-rich multi-copy suppressor) of Saccharomyces cerevisiae was isolated by the ability to suppress the temperature sensitivity of the htr1 disruptant (Kikuchi et al. (1994) Mol. Gen. Genetics, in press) by increasing its gene dosage. The predicted gene product contains a serine-rich domain followed by a putative transmembrane region. The SMS1 gene was physically and genetically mapped in the region near cdc3 on chromosome XII R.

Effect of intramedullary procaine injection on tracheal tone and phrenic neurogram

To map the superficial locations which are involved in the control of respiration and tracheal smooth muscle tone in ventrolateral medulla, we examined the effects of local anesthesia on phrenic activity and tracheal tone in twelve anesthetized, paralyzed, and artificially ventilated dogs. 0.5 microliter of 5% procaine was injected 0.3 to 0.5 mm below the surface unilaterally to the ventral superficial layer (from the rostral part of the trapezoid body to the caudal hypoglossal rootlets and lateral from the pyramids to 5.5 mm from the midline), which included rostral, intermediate and caudal areas, and the area lateral to the hypoglossal rootlets. The peak amplitude of the integrated phrenic neurogram was decreased by procaine injection to the intermediate area and the area lateral to the hypoglossal rootlets. Tracheal tone decreased only by procaine injection to the intermediate area. In the intermediate area, some injections decreased either phrenic output alone or tracheal tone alone. These results suggest that the two ventral medullary areas, i.e. the intermediate and caudolateral parts, contain neural structures which are involved in the shaping of phrenic output, but only the intermediate area is involved in the regulation of tracheal tone. It is also suggested that, in the intermediate area, the structures responsible for the maintenance of respiration and tracheal tone are, at least in part, separable.

Non-invasive monitoring of tissue response to radiotherapy by localised proton spin-lattice relaxation time in mice

Proton spin-lattice relaxation time T1 of the localised tumour portion and its neighbouring portion of tumour-bearing mice legs is successively observed before and after radiotherapy by applying the previously proposed magnetic focusing method. Changes in T1 values are also compared with the histological radiation effects. For un-irradiated tumours, T1 increases gradually with tumour growth. T1 of the tumour portion shows significant decrease after radiotherapy. The decrease in the T1 values of the tumour clearly depends on the single radiation dose of 30, 45 and 60 Gy, respectively. A rapid decrease in the T1 values of the tumour occurs prior to the decrease in tumour volume. These decreases in the T1 values of the tumour after radiotherapy correspond positively to the increase of the histological radiation effects. After the reduction in the T1 values of the irradiated tumour portion, a successive increase in T1 values is observed and suggests local recurrence of the tumour. These results show that localised T1 relaxation time is a good reflection of the tissue response to radiotherapy.

[Acute lymphoblastic leukemia accompanied by severe hypercalcemia; successful treatment with bisphosphonate]

A 62-year-old woman was admitted to the hospital because of bone pain. Laboratory data showed blasts in the peripheral blood, hypercalcemia (corrected calcium 15.1 mg/dl) and an increased level of parathyroid hormone related-protein (PTHrP). Bone marrow aspiration revealed increased lymphoblasts (96.5%), indicating acute lymphoblastic leukemia (ALL, L1). Subsequent radiological examination disclosed bone infiltration of ALL. Although the hypercalcemia was successfully treated with bisphosphonate, the PTHrP level remained high. After chemotherapy, the blasts in the peripheral blood disappeared and the PTHrP level normalized. We hypothesize that in the present case the production of PTHrP by lymphoblasts resulted in the hypercalcemic state. Although ALL is rarely accompanied by hypercalcemia, this case might help us to understand the relationship between ALL and hypercalcemia.

[Circumvention of cisplatin resistant ovarian cancer cells by antiestrogens]

Antiestrogens (AEs) have been considered to elicit antitumor effects via estrogen receptor. However, recent reports have demonstrated that AEs had an antitumor effect even in cases without estrogen receptor, and that AEs caused various kinds of biological behavior such as a chemosensitizing effect. We therefore investigated the possibility of circumvention of cisplatin (CDDP) resistance due to the chemosensitizing effect of AEs by using 5 ovarian cancer cell lines. They were named KF, MH, KK, KFra and KFrb cell lines. KF and MH were derived from serous cystadenocarcinomas, and KK from a clear cell carcinoma. KFra and KFrb were CDDP-resistant cell lines developed from the KF cell line. MCF-7 cell line derived from breast cancer was used as a control. The study of a 50% inhibitory concentration (IC50) revealed that clomiphene (CLO) had the most potent antiproliferative effect among the AEs used, and was followed by tamoxifen (TAM) and toremifene (TOR) with a similar effect. On the whole, the degree of CDDP sensitivity was not correlated with the degree of AE sensitivity. KFra cell line which had the highest CDDP-resistance among the 5 ovarian cancer cell lines used was the most sensitive to AEs, especially to CLO. In the study on the combined administration of CDDP and AEs, 1 microM of CLO significantly reduced the IC50 of CDDP to KFrb, KK and MCF-7 cell lines. Similarly, 1 microM of TAM significantly reduced the IC50 of CDDP to KF, KFra and MCF-7 cell lines, and 1 microM of TOR significantly reduced it to KFra, KK and MCF-7 cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Unsei-in inhibits rheological activity of leukocytes: mechanism of action in neutrophil-related skin diseases

To investigate the efficacy of Unsei-in on skin diseases such as Behçet's disease, palmoplantar pustulosis and psoriasis vulgaris, the rheological activity of leukocytes as manifested by adhesiveness, deformability and aggregability was studied in vitro using a micropore filtration method. Unsei-in inhibited the rheological activity of leukocytes at a statistical significance of p < 0.01 in normal individuals whose leukocytes had been stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP). It did not, however, inhibit the activity of cells that had not been stimulated by FMLP. In contrast, in Behçet's disease, Unsei-in inhibited rheological activity of non-stimulated leukocytes (p < 0.01) but did not inhibit the rheological activity of FMLP-stimulated leukocytes. In a study using Ouren-gedoku-to and Shimotsu-to, the main constituents of Unsei-in, the latter inhibited the activity of FMLP-stimulated leukocytes in normal individuals (p < 0.02). These results indicate that Unsei-in has an inhibitory effect on rheologically-activated neutrophils, which are involved in the healing mechanisms of the above skin diseases, and it also has a satisfactory effect in the form of a mixture of Shimotsu-to and Ouren-gedoku-to.

Defective IL-5-receptor-mediated signaling in B cells of X-linked immunodeficient mice

Murine (m) IL-5 induces proliferation and differentiation of both Ly-1+ B cells and activated conventional B cells. X-linked immunodeficient (XID) mice do not respond to thymus-independent type II antigens, and have an abnormal response to a variety of activation signals through Ig receptors, CD40 and cytokine receptors. Furthermore, XID mice show a B cell specific defect, reflected in decreased numbers of IL-5R alpha+ B cells and reduced responsiveness of IL-5R alpha+ B cells to mIL-5. We generated IL-5R alpha transgenic (5R alpha-Tg) mice in which B cells expressed recombinant IL-5R alpha. We crossed male 5R alpha-Tg mice with female XID mice and used their offspring to determine the IL-5 responsiveness of these B cells. All B cells of F1 male mice carrying the xid gene together with the transgene expressed the recombinant IL-5R alpha. However, those mice lacked Ly-1 B cells and their B cells acquired responsiveness to mIL-5. Interestingly, XID-5R alpha-Tg B cells, but not XID B cells, acquired mIL-5 proliferative and Ig-secretory responsiveness only in the presence of suboptimal doses of lipopolysaccharide. Stimulation of these B cells with mIL-5 plus phorbol myristate acetate induced proliferation, but not Ig secretion. These results indicate that the impaired mIL-5 responsiveness of B cells in XID mice is due to an abnormality of IL-5R-mediated signaling which may correlate with the xid gene mutation, alteration of a single amino acid of Bruton's tyrosine kinase.

Characteristics of body shape of female athletes based on factor analysis

We examined the body shape of female athletes in comparison with female adult non-athletes by factor analysis. The subjects were 433 adult non-athletes and 464 athletes participating in 11 different sporting events. The physique, skinfold thickness and body composition of each subject were measured. The values obtained from non-athletes were analyzed by factor analysis, and the body shape of the athletes was then analyzed according to these factors. Four main factors with which 80 percent of total variance could be explained were body fat (Factor 1), mass (Factor 2), leg length to height ratio (Factor 3) and length (Factor 4), and were extracted from the values from non-athletes. The body shape of the athletes could be classified into 4 categories by cluster analysis for factor score of sporting events: less body fat and slim type, average type like non-athletes, muscular and well-balanced type, and tall and well-developed mass. Compared with non-athletes, female athletes for all sporting events had less body fat. Moreover, the athletes had a body shape suitable for their sporting events; i.e., their mass, length of leg and height.

Role of hypoxia on increased blood pressure in patients with obstructive sleep apnoea

BACKGROUND

Cyclical changes in systemic blood pressure occur during apnoeic episodes in patients with obstructive sleep apnoea (OSA). Although several factors including arterial hypoxaemia, intrathoracic pressure changes, and disruption of sleep architecture have been reported to be responsible for these changes in blood pressure, the relative importance of each factor remains unclear. This study assessed the role of hypoxaemia on the increase in blood pressure during apnoeic episodes.

METHODS

The blood pressure in apnoeic episodes during sleep and the blood pressure response to isocapnic intermittent hypoxia whilst awake were measured in 10 men with OSA. While asleep the blood pressure was measured non-invasively using a Finapres blood pressure monitor with polysomnography. The response of the blood pressure to hypoxia whilst awake was also measured while the subjects intermittently breathed a hypoxic (5% or 7% oxygen) gas mixture. Each hypoxic gas exposure was continued until a nadir arterial oxygen saturation (nSaO2) of less than 75% was reached, or for a period of 100 seconds. The exposure was repeated five times in succession with five interposed breaths of room air in each run.

RESULTS

The mean (SD) increase in blood pressure (delta MBP) during apnoeic episodes was 42.1 (17.3) mm Hg during rapid eye movement (REM) sleep and 31.9 (12.5) mm Hg during non-REM sleep. The delta MBP during apnoeic episodes showed a correlation with the decrease of nSaO2 (delta SaO2) (r2 = 0.30). The change in blood pressure in response to intermittent hypoxia whilst awake was cyclical and qualitatively similar to that during apnoeic episodes. Averaged delta MBP at an SaO2 of 7% and 5% oxygen was 12.6 (5.7) and 13.4 (3.6) mm Hg, respectively, whereas the averaged delta MBP at the same delta SaO2 during apnoeic episodes was 38.4 (15.5) and 45.2 (20.5) mm Hg, respectively.

CONCLUSIONS

The blood pressure response to desaturation whilst awake was about one third of that during apnoeic episodes. These results suggest that factors other than hypoxia may play an important part in raising the blood pressure during obstructive sleep apnoea.

Synthesis and self-cleavage reaction of a chimeric molecule between RNase P-RNA and its model substrate

We synthesized a chimeric RNA between the catalytic RNA subunit of RNase P from Escherichia coli (M1 RNA) and a model substrate of the enzyme. The model substrate is the smallest substrate of RNase P, having a simple stem-loop structure. This model substrate was added to the 3'-end of M1 RNA. This chimeric molecule, which we call M1 RNA-MS, is a self-cleaving RNA and is cleaved much more efficiently than the M1 RNA-pre-tRNA, an artificial self-cleaving RNA previously synthesized [Kikuchi et al. (1993) Nucleic Acids Res. 21, 4685-4689], that consists of a full-size tRNA precursor and the M1 RNA. The self-cleavage of M1 RNA-MS at 10 mM Mg2+ was an intramolecular reaction (cis-cleavage). Ca2+ supported the self-cleavage of M1 RNA-MS as effectively as Mg2+, although the self-cleavage of M1 RNA-pre-tRNA proceeded with low efficiency in the presence of Ca2+ as the only metal ion. Future application of the M1 RNA-MS molecule to the in vitro evolution of the M1 RNA and other experiments is proposed.