Asparaginase II of Saccharomyces cerevisiae. Characterization of the ASP3 gene

Purified preparations of asparaginase II of Saccharomyces cerevisiae exhibit two protein bands upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cloning and sequencing of the ASP3 gene, and partial amino acid sequencing as asparaginase II, imply that both bands are encoded by ASP3 but have different N termini. Northern blot analysis using the cloned ASP3 gene as a probe indicates that nitrogen catabolite repression of asparaginase II is achieved by alteration in mRNA levels. Deletion of sequences greater than 600 base pairs upstream from the initiation AUG codon results in an altered response to certain nitrogen sources in strains containing the truncated gene.

GH secretory dynamics and responsiveness to SMS 201-995 treatment in acromegaly

Recently, SMS 201-995, a long acting somatostatin analogue, has been used in successful therapy for inhibition of growth hormone (GH) levels in acromegaly. But, it was reported that inhibitory and clinical effects in the individual patient were different in many cases. Therefore, to find the predictive factor for patients with effective inhibition of GH, we investigated the paradoxical response to thyrotropin releasing hormone (TRH), growth hormone releasing hormone (GHRH) and diurnal variation of GH secretion between responders and non-responders to SMS 201-995. The results were as follows; Responders, patients with suppressive response to SMS 201-995, totalled 4 of 8 patients. The paradoxical response of GH to TRH was observed in 3 of 4 responders and 3 of 4 non-responders. The response of GH to GHRH was not noted in either of the groups. The diurnal variation of GH secretion showed in one of the responders and in 3 of the non-responders. These results suggested that the absence of diurnal variation of GH secretion was a characteristic feature of responders to SMS 201-995 and thus diurnal variation of GH secretion could be used as a predictive factor for SMS 201-995 therapy, and the pathogenetic mechanism of acromegaly might be dependent on the controlled regulation of GHRH and endogenous somatostatin.

Solid and papillary epithelial neoplasms of the pancreas: CT findings

Five female patients and one male patient with solid and papillary epithelial neoplasms of the pancreas were examined with computed tomography (CT). The mean age of the patients was 27 years (range, 13-46 years). All cases showed well-encapsulated, round or lobulated masses consisting of both cystic and solid areas. Cystic portions showed CT numbers that suggested hemorrhagic necrosis. There were no internal septations within the masses. In three tumors located in the head of the pancreas, dilatation of the biliary tree was absent or minimal, although the masses were large. Two tumors contained calcifications. One tumor demonstrated metastatic deposits in liver and lymph nodes. Metastatic masses appeared similar to the primary pancreatic mass. Solid and papillary neoplasm of the pancreas should be the primary diagnostic consideration when characteristic CT findings are detected in a young female patient.

Diagnosis of epiphrenic esophageal diverticulum by computed tomography

Epiphrenic diverticulum is typically demonstrated by computed tomography examination as a thin walled, air or air-fluid filled structure communicating with the esophagus. However, those not associated with a distal esophageal obstruction (stricture, achalasia) may remain contracted in resting state and thus may not be visible. Occasionally the diverticulum may have to be differentiated from mediastinal abscess or tumors and even hiatus hernia.

Mortality among workers at a butadiene facility

Several studies of styrene-butadiene rubber (SBR) workers have reported excess cancers at various sites; however, little could be concluded concerning specific etiologic agents because of the multiple exposures encountered by these groups. The current study examined cause-specific mortality in a cohort of 2,586 male workers employed for at least 6 months between 1943 and 1979 in a butadiene manufacturing plant that supplied butadiene to two SBR plants. Standardized mortality ratios were calculated using national (NSMR) and local (LSMR) comparison populations. The all-cause NSMR was 80 (p less than 0.05) and the all-cancer NSMR was 84; the corresponding LSMRs were 96 and 76 (p less than 0.05). No significant excesses were observed for any cause of death except lymphosarcoma and reticulum cell sarcoma (NSMR = 235). When the cohort was subdivided into routine, nonroutine, and low-exposure groups, the SMRs were consistently elevated for this cause of death in all three groups. However, direct comparisons between each of the two exposure groups and the low-exposure group were inconsistent. This suggests butadiene may not be responsible for the excess, but the association deserves close attention in future studies.

Adjuvant treatment of operable stomach cancer with polyadenylic.polyuridylic acid in addition to chemotherapeutic agents. Differential effect on natural killer cell and antibody-dependent cellular cytotoxicity

Peripheral blood lymphocytes of operable stomach cancer patients were evaluated sequentially for their natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities before and after chemotherapy in association with polyadenylic.polyuridylic acid [poly(A).poly(U)]. Their cytotoxicity was measured by 4 h-chromium release assays, using human K562 and sensitized murine L1210 cells as targets for assays of NK and ADCC respectively. The mean NK cytotoxicity of 89 patients before treatment was significantly lower than that of the 18 sex- and age-matched healthy controls, whereas assays of ADCC showed similar levels of cytotoxicity in both groups. Patients who had received postoperative chemotherapy (5 fluorouracil, 12 mg/kg and adriamycin, 40 mg/M2) once, had, 5 days after injection, NK cytotoxicity levels similar to those before treatment. For these patients, an additional administration of poly(A).poly(U) (100 mg) resulted, 2 days later, in a significant increase in the levels of NK cytotoxicity without affecting the levels of ADCC. Repeated injections of poly(A).poly(U) alternated with chemotherapy induced, consistently, exclusive enhancement of NK activity after each injection. These results suggest that the effector cells for NK and ADCC activities are of functionally different cell populations.

Studies on changes of beta-adrenergic receptors in polymorphonuclear cell and mononuclear cell with the changes of thyroid function

Although it has been well established that thyroid hormones increase β-adrenergic receptors of various tissues in the animal studies, there are controversies about the β-adrenergic receptor changes of human mononuclear cells and polymorphonuclear cells. The present study was performed to analyze the change of β-adrenergic receptor of those cells according to the thyroid functional status and to evaluate their usefulness in assessment of sympathetic hyperactivity. We measured [³H]-dihydroalprenolol binding to circulating mononuclear and polymorphonuclear cells from 18 patients with hyperthyrodism, 7 with hypothyroidism, 8 with euthyroid goiter and 21 normal controls. Only with polymorphonuclear cells the receptor concentration was significantly higher (P<0.01) in hyperthyroidism (46.07±4.78 fmol/mg protein) than in the normal control (28.42±2.06 fmol/mg protein) and the affinity constants of both cells were comparable to normal control values. And serum concentrations of T₃ were not correlated well with the changes of receptor concentrations in hyperthyroidism. The patients with hypothyroidism and euthyroid goiter showed no significant difference in the receptor concentration and the affinity constants with both cell binding assays. These results indicate that thyroid hormones increase the receptor concentration in polymorphonuclear cells which might be responsible for the symptoms of sympathetic hyperactivity and the polymorphornuclear cells are useful for β-adrenergic receptor assay.

Postprandial 2-hr C-peptide concentration as a guide for insulin treatment in patient with NIDDM

To determine the usefulness of postpradial-2hr serum C-peptide as a guide for insulin treatment in NIDDM, the 67 NIDDM patients admitted in Kyung Hee University Hospital from Nov. 1981 to May 1984 were classified according to postprandial 2-hr insulin, C-peptide levels and 24-hr urine C-peptide levels. The patients were divided into 3 groups according to the level of insulin or C-peptide in normal persons reported previously. In 22 patients with postprandial 2-hr values of more than 5.8 ng/ml for C-peptide, 12 patients (55%) were diet controllable and only 5 patients (22%) required insulin treatment. On the other hand, in the classification according to postprandial 2-hr insulin or 24-hr urine C-peptide levels, higher response groups should be controlled by diet alone, but 9 of 18 patients (50%) for insulin, 8 of 14 patients (57%) for 24-hr urine C-peptide required insulin treatment. The classification according to postprandial 2hr C-peptide levels was a more sensitive guide for insulin treatment than that with postprandial 2hr insulin level or 24hr urine C-peptide level.

The changes of serum-ACE, plasma renin activity and aldosterone in the diabetics with hypertension

It is well known that the serum-ACE levels are elevated in sarcoidosis, Gaucher’s disease, and some granulomatous diseases. Recently, the serum-ACE level was also found to be elevated in diabetes mellitus. To confirm the possible role of plasma renin activity and aldosterone in the pathogenesis of hypertension and to assess the relationship of serum ACE to the plasma renin activity and aldosterone profiles in diabetics, we measured the levels of serum ACE, plasma renin activity, aldosterone and blood pressure in 38 diabetic patients who were admitted to Kyung Hee University Hospital from June 1981 to September, 1982. The results were as follows: The S-ACE activity was significantly elevated in 38 patients with diabetes mellitus (9.42±6.60 Unit) as compared with that in the healthy controls (2.53±1.54 Unit) (p<0.005) (p<0.005). The S-ACE activity was significantly elevated in 15 hypertensive diabetics (14.29± 7.10 Unit) as compared with that in 23 normotensive diabetics (6.24±3.68 Unit) (p<0.005). The S-ACE activity was elevated in 15 diabetic patients with retinopathy (10.6±4.7 Unit) as compared with the levels in 17 diabetic patients without retinopathy (6.7±4.8 U) (p<0.05). The S-ACE activity was directly correlated to the mean arterial pressure (r=0.54) (p<0.005). The plasma renin activity and aldosternone concentrations in diabetics were not different from the normal controls and had no correlationship to the S-ACE activity. After 2 weeks of insulin therapy in 15 diabetics, the S-ACE activity was not changed.

Effect of beta-endorphin and cortisol on the PHA stimulated lymphoblastogenesis

The mechanism of immune suppression in a severely stressful condition is not known. Since the demonstration of β-endorphin receptor on the surface of the circulating lymphocyte, it was reported that β-endorphin could suppress PHA stimulated lymphoblastogenesis. Because the concentration of β-endorphin was supraphysiologically high, it is doubtful that β-endorphin can suppress the lymphoblastogenesis directly in vivo. We investigated the suppression of PHA stimulated lymphoblastogenesis by β-endorphin in vitro and the effect of β-endorphin in some conditions where β-endorphin increases in vivo. PHA induced lymphoblastogenesis of T lymphocyte was maximal at the concentration of 5 μg/ml. β-endorphin could not suppress the blastogenesis even at the highest concentration. In the five healthy men who received metyrapone the previous night, PHA stimulated blastogeneses were not significantly suppressed. In a patient with Nelson’s syndrome, the lymphoblastogenesis was suppressed at all concentrations of PHA. Cortisol significant suppressed the blastogenesis even at the concentration of 10 μg/dl and its suppressive effect was shown in dose dependant manner. Our results suggested that β-endorphin could not suppress the lymphoblastogenesis directly in vivo.

Asparaginase II of Saccharomyces cerevisiae: positive selection of two mutations that prevent enzyme synthesis

A positive selection method, D-aspartic acid beta-hydroxamate resistance, was used to isolate Saccharomyces cerevisiae strains lacking the ability to synthesize asparaginase II. Of 100 such mutant strains, 93 exhibited mutations which were allelic with asp3, a previously characterized mutation. The other seven strains carried a new mutation, asp6. The asp6 mutation segregated 2:2 in asp6 X wild-type crosses and assorted from the asp3 mutation in asp6 X asp3 crosses. All seven asp6 mutant isolates reverted at a relatively high frequency, whereas the asp3 mutant isolates did not revert under the same conditions. Various independent asp3 isolates were mated to give heteroallelic diploids, which when sporulated and spread on D-asparagine medium yielded no recombinant strains.

Asparaginase II of Saccharomyces cerevisiae: comparison of enzyme stability in vivo and in vitro

Asparaginase II of Saccharomyces cerevisiae is a cell wall mannan containing glycoprotein. Recent studies have demonstrated that asparaginase II activity increases in exponentially growing cell cultures and then decreases as the cells enter the stationary phase. Enzyme inactivation has been attributed to a Zn2+-dependent protease which is synthesized de novo during the late exponential phase [Pauling, K.D., & Jones, G.E. (1980) J. Gen. Microbiol. 117, 423-430; Pauling, K.D., & Jones, G.E. (1980) Biochim. Biophys. Acta 616, 271-282]. We have investigated the mechanism of asparaginase II inactivation using both whole cell suspensions and highly purified enzyme. Our data indicate that the rate of asparaginase II inactivation in cell suspensions is primarily influenced by pH changes that occur as a consequence of cell growth and glucose fermentation and that enzyme inactivation is not dependent on Zn2+ or on de novo protein synthesis. Also, in vitro studies with purified enzyme show kinetics of inactivation that are similar to those observed in vivo. Consequently, involvement of a yeast protease in the inactivation process is relatively unlikely.

Transport and metabolic effects of alpha-aminoisobutyric acid in Saccharomyces cerevisiae

alpha-Aminoisobutyric acid is actively transported into yeast cells by the general amino acid transport system. The system exhibits a Km for alpha-aminoisobutyric acid of 270 microM, a Vmax of 24 nmol/min per mg cells (dry weight), and a pH optimum of 4.1-4.3. alpha-Aminoisobutyric acid is also transported by a minor system(s) with a Vmax of 1.7 nmol/min per mg cells. Transport occurs against a concentration gradient with the concentration ratio reaching over 1000:1 (in/out). The alpha-aminoisobutyric acid is not significantly metabolized or incorporated into protein after an 18 h incubation. alpha-Aminoisobutyric acid inhibits cell growth when a poor nitrogen source such as proline is provided but not with good nitrogen sources such as NH+4. During nitrogen starvation alpha-aminoisobutyric acid strongly inhibits the synthesis of the nitrogen catabolite repression sensitive enzyme, asparaginase II. Studies with a mutant yeast strain (GDH-CR) suggest that alpha-aminoisobutyric acid inhibition of asparaginase II synthesis occurs because alpha-aminoisobutyric acid is an effective inhibitor of protein synthesis in nitrogen starved cells.