Cleavage of prosomatostatins by the yeast Yap3 and Kex2 endoprotease

A previous in vivo study implicated the YAP3 and KEX2 genes in the proteolytic maturation of anglerfish prosomatostatins which were heterologously expressed in the yeast Saccharomyces cerevisiae. In the present report, we have determined the cleavage specificity of these enzymes by incubating them in vitro with synthetic peptides mimicking the potential processing sites present in the somatostatin precursors and with full length prosomatostatin I. The Yap3 enzyme was prepared from a membrane fraction of a YAP3-overexpressing yeast, and a soluble form of Kex2 obtained from the culture medium of insect cells which had been infected with a recombinant baculovirus expressing the KEX2 gene. The identity of the cleavage products was confirmed by amino acid analysis. Our results show that both endoproteases generate mature SRIF-28 from prosomatostatin-II but that only Yap3 can process the homologous monobasic cleavage site (ie single arginine residue) found in prosomatostatin-I. Both enzymes were also shown to recognize the Arg-Lys doublet found in prosomatostatin-I producing a lysine-extended form of SRIF-14, which indicates that cleavage occurred C-terminal to the arginine residue. In addition, Kex2 also hydrolyzed C-terminal to the Pro-Arg motif to release a tripeptide-extended form of SRIF-14. However, neither endoprotease could cleave after the Arg-Lys doublet to release mature SRIF-14. Taken together, our results indicate that the yeast Kex2 and Yap3 endoproteases have distinct, though overlapping, substrate specificities. The results also strongly support the role of Yap3 as a proprotein convertase which perhaps defines a new family of processing enzymes.

Influence of ventricular morphology on diastolic filling performance in double-inlet ventricle after the Fontan procedure

OBJECTIVES

The purpose of this study was to define the influence of dominant chamber morphology on ventricular performance after the Fontan procedure in patients with double-inlet ventricle.

BACKGROUND

Previous studies have reported the impact of ventricular morphology on preoperative ventricular performance and surgical outcome. However, the influence on postoperative ventricular performance has not been addressed.

METHODS

Twenty-six clinically asymptomatic patients > 1 year after repair (mean age at procedure 6.1 +/- 3.7 years) were evaluated with ventricular cineangiography and radionuclide blood pool studies (18 with a dominant left ventricular morphology [LV group], 8 with a dominant right ventricular morphology [RV group]) and compared with normal control subjects.

RESULTS

Ventricular volume, mass and systolic variables were similar between patient groups. In the LV group, however, the mass/volume ratio was significantly elevated compared with values in control subjects (1.11 +/- 0.28, 0.97 +/- 0.19, p < 0.05), whereas this ratio in the RV group (0.90 +/- 0.11) was within the normal range and significantly lower than that in the LV group (p < 0.05). Mean right atrial and pulmonary artery pressures in the RV group were significantly higher than those in the LV group (p < 0.05). Peak filling rates (2.87 +/- 0.70, 2.41 +/- 1.15 and 3.84 +/- 0.51 end-diastolic volume/s [LV and RV groups and control subjects, respectively]) were significantly lower in both groups than in control subjects (p < 0.001), without intergroup difference.

CONCLUSIONS

Ventricular filling abnormalities after atrial to pulmonary anastomosis are common regardless of the type of dominant ventricular morphology, and these abnormalities in patients with dominant right ventricular morphology do not coexist with ventricular hypertrophy. Such diastolic abnormalities may be related to either intrinsic myocardial or acquired factors, not to excessive hypertrophy alone. Those differences may become clinically more apparent with longer follow-up and may raise concerns over the long-term course.

Introns are essential for growth-regulated expression of the mouse thymidylate synthase gene

The thymidylate synthase (TS) gene is expressed at much higher levels in proliferating cells than in quiescent cells. We have been studying the sequences that are important for regulating the mouse TS gene. We previously showed that DNA sequences upstream of the essential promoter elements as well as downstream of the ATG codon are both necessary (but neither is sufficient) for normal regulation in growth-stimulated cells. In the present study, we examined the possible roles of the coding region, polyadenylation signal, and introns as downstream regulatory elements. Minigenes consisting of 1 kb of the TS 5'-flanking region, the coding region (with or without various introns at their normal locations), and polyadenylation signals from the TS gene, the human beta-globin gene, and the bovine growth hormone gene were stably transfected into wild-type mouse 3T6 cells. Minigenes that contained introns 5 and 6, 1 and 2, or 1 alone were regulated regardless of which polyadenylation signal was included. A minigene that contained an internally deleted version of intron 1 was also regulated in response to growth stimulation. However, when all introns were omitted, there was little if any change in the level of minigene expression as cells progressed from G1 through S phase. These observations indicate that TS introns contain sequences that are necessary for normal growth-regulated expression of the mouse TS gene. These sequences appear to be associated with sequences that are important for splicing and to function in cooperation with upstream regulatory elements to bring about normal S-phase-specific expression.

Isolation and characterization of S. cerevisiae mutants defective in somatostatin expression: cloning and functional role of a yeast gene encoding an aspartyl protease in precursor processing at monobasic cleavage sites

The peptide somatostatin exists as two different molecular species. In addition to the most common form, somatostatin-14, there is also a fourteen amino acid N-terminally extended form of the tetradecapeptide, somatostatin-28. Both peptides are synthesized as larger precursors containing paired basic and monobasic amino acids at their processing sites, which upon cleavage generate either somatostatin-14 or -28, respectively. In some species of fish two distinct, but homologous, precursors (prosomatostatin-I and -II) give rise to somatostatin-14 and -28, respectively. Whereas anglerfish prosomatostatin-II was previously shown to release exclusively somatostatin-28, the yeast Saccharomyces cerevisiae proteolytically matures the homologous prosomatostatin-I precursor to somatostatin-28 and -14 as well as to a lysine-extended form of somatostatin-14. The Kex2 endoprotease appears to be essential for the formation of lysine somatostatin-14 and is involved either directly or indirectly in the release of mature somatostatin-14. The isolation of yeast mutants defective in somatostatin-28 expression (sex mutant) allowed the cloning of a non-essential gene, which encodes an aspartyl protease, whose disruption severely affects the cleavage of mature somatostatin-28 from both somatostatin precursors. We conclude that two distinct endoproteases, which demonstrate some cross specificity in vivo, are involved in the proteolytic maturation of prosomatostatin at mono- and dibasic processing sites in yeast.

Ventricular performance before and after Fontan repair for univentricular atrioventricular connection: angiographic and radionuclide assessment

OBJECTIVES

This study was designed to evaluate changes in ventricular volume, mass and cardiac function before and after creation of an atrial to pulmonary connection in patients with a univentricular atrioventricular connection.

BACKGROUND

Intact systolic and diastolic performance is critical for successful establishment of an atrial dependent circulation, and few studies are available comparing cardiac performance before and after creation.

METHODS

With the use of radionuclide blood pool imaging and ventricular cineangiography, 54 patients (mean age 6.4 +/- 3.4 years) were studied. Twenty-eight patients were investigated preoperatively and 36 greater than 1 year after repair and compared with a control population.

RESULTS

Before operation, end-diastolic volume and wall mass were significantly increased compared with those of control subjects; however, the mass/volume ratio was normal (1.08 +/- 0.31 g/ml for the preoperative group; 0.97 +/- 0.19 for control subjects). Although end-diastolic volume returned to normal after the procedure, wall mass remained elevated and contributed to an elevated mass/volume ratio (1.20 +/- 0.38 g/ml). After the procedure, systemic vascular resistance index was significantly elevated compared with that before surgery or with that of control subjects (1,199 +/- 373, 2,120 +/- 645, 1,556 +/- 275 dynes.s.cm-5.m2: pre- and postrepair and control subjects, respectively). Radionuclide studies demonstrated that preoperative ejection fraction (52 +/- 9, 50 +/- 9, 60 +/- 8%), peak ejection (2.58 +/- 0.66, 2.95 +/- 0.81, 3.73 +/- 0.70 EDV/s) and peak filling rates (2.84 +/- 0.75, 2.75 +/- 0.79, 3.84 +/- 0.51 end-diastolic volumes [EDV/s]) were significantly reduced compared with those of control subjects and remained so after surgery.

CONCLUSIONS

These data suggest that systolic and diastolic function is depressed preoperatively in these patients, remains unchanged after the creation of an atrial-dependent circulation and is associated with an increased systemic vascular resistance. Long-term issues addressing preservation of cardiac function need to be prospectively studied.

Evaluation of ventricular diastolic function in normal children using equilibrium radionuclide angiography

Twenty children, aged 10.3 +/- 4.5 (3.3 to 17.5) years, were studied by equilibrium radionuclide angiography to establish a normal range for diastolic parameters. Ejection fraction (EF), peak ejection rate (PER) and time to peak ejection rate (TPER), peak filling rate (PFR) and time to peak filling rate (TPFR) were obtained from ventricular time-activity curves and their first derivative curves, and PFR and TPFR were considered as the diastolic parameters. Normal ranges obtained were as follows: EF, 60 +/- 8%; PER, 3.73 +/- 0.70 EDV-1; TPER, 109 +/- 25 ms; PFR, 3.84 +/- 0.51 EDVs-1; TPFR, 136 +/- 21 ms. There were significant correlations between PER and EF (P less than 0.001), PFR and EF (P less than 0.05), while age and heart rate had no influence upon these variables. Such normal ranges will be useful for evaluation of systolic and diastolic function in children with heart disease.

Maximal work capacity and dietary status of rural black South African schoolboys aged 10-14 years

The anthropometric and physical characteristics, nutritional status, exercise habits and physiological response to maximal exercise of 22 rural black schoolboys aged 9.5 to 14.5 years, attending a local farm school on the outskirts of Johannesburg, were studied. Kilojoule intake ranged from 37% to 41% of the recommended daily allowance and percentage body fat was correspondingly low. Protein intake was, however, satisfactory and there was no evidence of stunted or wasted growth. Maximum oxygen consumption (VO2 max) ranged from 48.9 ml/kg/min to 50.6 ml/kg/min and 1.55 l/min to 2.01 l/min. Despite partially inadequate nutritional intakes and regular exposure to pollutants, the maximal work capacity of these subjects compares favourably with the age-related ranges of VO2 max reported by previous researchers. A possible adaptation to nutritional and environmental stress is suggested.

A systems approach to planning biomedical information services

A systems approach to planning was applied within the Biomedical Information Communication Center at Oregon Health Sciences University when its User Services division launched a strategic planning effort. By looking at the choice subsystem, the organizational structure, and the behavioral subsystem, those engaged in planning attempted to assure that desired change would permeate the entire system. The challenge of applying a theoretically ideal planning model within an environment averse to planning is delineated.

Quantitative assessment of blood flow in pediatric recipients of renal transplants

We applied a renal blood flow (RBF) quantification technique to pediatric data, which depends minimally on bolus shape, uses a conventional radiopharmaceutical 99mTc-DTPA, and generates a value for RBF as a percentage of cardiac output (RBF/CO). Mean RBF was 16.9% (+/- 4.8) for normal transplants, 13.1% (+/- 2.9) for transplants undergoing mild-to-moderate chronic rejection, 7.9% (+/- 1.3) for those with mild acute rejection and 3.3% (+/- 1.4) for those with moderate-to-severe acute rejection. Very low blood flow values within 24 hr following transplantation may have prognostic significance. Patients who required transplant-nephrectomy had significantly lower RBF/CO values than children who retained their allograft.

Lambdoid synostosis. Part 2: Review of cases managed at The Hospital for Sick Children, 1972-1982

Seventy-four patients with premature union of the lambdoid suture were treated at The Hospital for Sick Children during the years 1972 through 1982. Lambdoid synostosis is considered to be a rare form of craniosynostosis, but this is more likely due to lack of recognition rather than to infrequent occurrence. The skull deformity resulting from lambdoid synostosis is often mistakenly attributed to positional molding rather than to actual synostosis. When the lambdoid suture closes, the occiput on the involved side is flat, the forehead on the same side tends to bulge forward, and the ear on this side adopts a low and forward position. Skull x-ray films may demonstrate obliteration of the lambdoid suture, but more frequently one sees sclerosis along one edge of the closing suture. Radionuclide bone scanning will show increased activity during the active phase of union and decreased or absent activity once union has occurred. Craniectomy performed during the neonatal period will correct the deformity and provide for normal cranial growth. Delay in surgery beyond 6 months will frequently necessitate a more extensive cranial repair.

Congenital unilateral pulmonary vein stenosis complicating transposition of the great arteries

Four patients with transposition of the great arteries and unilateral pulmonary vein (PV) stenosis, all left-sided, were studied. Two patients had an intact ventricular septum (1 with a patent ductus arteriosus), 1 patient had a ventricular septal defect and 1 had a ventricular septal defect with pulmonary stenosis. Clinical signs, such as recurrent pneumonia, unilateral pulmonary edema and pleural effusion, were present preoperatively in 2 patients. Diagnosis was made at cardiac catheterization by cineangiography in 2 patients and at Mustard operation when the PV orifices were inspected in the other 2. PV dilatation was attempted in 3 patients, 1 before correction (age 6 months), 1 during and after it (ages 1 and 3 years, respectively) and 1 during corrective surgery (age 15 months). In the fourth patient only the intracardiac baffle was enlarged near the left PV orifices. In the first patient, at Mustard operation (age 18 months), only a fibrotic PV without an orifice was found; this patient died after surgery. The mean follow-up in the 3 survivors was 3.2 years (range 2 months to 7.6 years). All have severe residual PV obstruction documented by technetium-99m lung perfusion scans that show decreased flow to the left lung (0 to 16% total counts; normal 45%); 2 have unilateral pulmonary edema and 1 has pulmonary artery pressure at systemic level. It is believed that in patients with transposition of the great arteries, left-sided unilateral PV stenosis is a congenital anomaly that becomes progressive as a result of postnatal preferential flow to the right lung.

Accuracy of brain scanning in pediatric craniocerebral neoplasms

A total of 2,563 children were studied by cerebral radionclide angiography, immediate postinjection blood-pool imaging, and delayed 2- to 4-hr. brain scanning. Of 110 new neoplasms of the brain or skull examined, 90% were detected by these means. The scan did not appear to be as accurate in craniopharyngiomas (6/10) and brainstem tumors (5/6). Thirty-nine recurrent tumors not studied previously all produced positive brain scans. Meticulous positioning of the pediatric patient is necessary at all times for accurate results.

Dural fluid collections in infants and children. A successful nuclear medical approach

The authors describe their experience in 94 cases of dural fluid collections. The correct diagnosis was made in 94%, which is attributed to (a) including radionuclide angiography and both an immediate and a two- to four-hour delayed scan for every patient undergoing brain studies, (b) a high index of suspicion, and (c) simultaneous interpretation of the scan and the skull film. The false-positive rate was 10%, as shown by cerebral angiography.

Library use of public health materials: description and anaylsis

A method is described for optimizing the efficiency of a journal collection. The method is employed to determine an optimal journal collection in public health. A citation analysis of 3,456 citations from the bibliographies of forty-four master's and doctoral dissertations from five different universities is performed. It is verified that the distribution of references to journal titles is approximately logarithmic (Bradford's Law) and that the distribution of references by year is exponential. These two parameters are combined to formulate an equation which may be used to specify a journal collection satisfying the greatest possible percent of demand. In public health, for example, a 1,500-volume library containing sixty titles could satisfy 73% of the demand for references in health related areas and 48% of the total demand for references for this particular, diverse research group. Other desirable aspects of a public health collection are also described as determined from the data.