Two histidine residues are essential for ribonuclease T1 activity as is the case for ribonuclease A

Ribonuclease T1 (RNase T1, EC 3.1.27.3) is a guanosine-specific ribonuclease that cleaves the 3',5'-phosphodiester linkage of single-stranded RNA. It is assumed that the reaction is generated by concerted acid-base catalysis between residues Glu-58 and His-92 or His-40. From the results of chemical modification and NMR studies, it appeared that the residue Glu-58 was indispensable for nucleolytic activity. However, we have recently demonstrated that Glu-58 is an important but not an essential residue for catalytic activity, using the methods of genetic engineering to change Glu-58 to Gln-58 etc [Nishikawa, S., Morioka, H., Fuchimura, K., Tanaka, T., Uesugi, S., Ohtsuka, E., & Ikehara, M. (1986) Biochem. Biophys. Res. Commun. 138, 789-794]. In the present paper, we report that mutants of RNase T1 with residue Ala-40 or Ala-92 have almost no activity, while mutants that contain Ala-58 retain considerable activity. These results show that the two histidine residues, His-40 and His-92, but not Glu-58, are indispensable for the catalytic activity of the enzyme. We propose a revised reaction mechanism in which two histidine residues play a major role, as they do in the case of RNase A.

12-O-tetradecanoylphorbol-13-acetate induces an immediate, but transient increase in mitotic activity uncoupled from DNA synthesis in the monolayer cultures of rat keratinocyte

A single wave of mitotic activity was observed in a monolayer culture of rat keratinocytes immediately after exposure to 12-O-tetradecanoylphorbol-13-acetate. A peak for cells in prophase, observed at 10 min after the exposure, was followed by a peak for metaphase at 20 min, for anaphase at 25 min and telophase at 30 min after the exposure. Thereafter, the mitotic activity began to subside. This transient stimulation of mitotic activity resulted in an increase of population density in the monolayer culture. There was neither a stimulation of DNA synthesis during this period nor a change of the DNA content after the mitotic activity was completed. This single burst of synchronous mitotic activity which did not require a substantial stimulation of DNA synthesis suggests that the effect was on the initiation process of mitosis among a subpopulation of cells, presumably cells delayed in the G2 phase of the cell cycle.

Pseudomosaicism for trisomy 13. Three case reports

Pseudomosaicism is of particular concern in prenatal diagnosis when it involves mosaicism for a cytogenetic abnormality associated with a clinical syndrome which is compatible with postnatal life, such as trisomies for chromosomes 13, 18, and 21. The lack of data regarding the outcome of pregnancies involving these specific kinds of pseudomosaicism makes genetic counselling difficult. Three cases of prenatal diagnosis of pseudomosaicism for trisomy 13, each of which had a normal outcome, will be presented (Tables 1 and 2). The three main areas for consideration are: (1) the genetic counselling issues, (2) the additional prenatal diagnostic options available to evaluate the status of the fetus in an attempt to identify some of the clinical features of trisomy 13, and (3) the outcome of the pregnancies.

Exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA) induces the synthesis of histidine-rich protein (filaggrin) in monolayer cultures of rat keratinocytes

The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent tumor promoter, on epidermal differentiation has been studied by investigating the appearance of the epidermal differentiative marker protein, histidine-rich protein (HRP), in monolayer cultures of rat keratinocytes grown in low-calcium (0.1 mM) medium. Monoclonal antibody, 3F6-6, raised against the 60K HRP (HRPII) derived from the epidermis of the newborn rat was utilized to detect HRP in cultured keratinocytes. As a major component of keratohyalin in the cells of the granular layer in epidermis, HRP is not normally found in a monolayer culture of rat keratinocytes containing a high population of proliferating cells. However, when these cultures were exposed to 10 ng/ml of TPA, DNA and protein synthesis were decreased by up to 95% and 60%, respectively, and the cells in the monolayer culture became HRP-positive within 18-24 h. TPA has been shown to cause a withdrawal of the basal cells from the cell cycle and a commitment of these cells to an accelerated rate of terminal differentiation. Exposure to TPA at the same time that the calcium level of the monolayer cultures was raised to 2.0 mM in order to allow stratification resulted in positive immunostaining for HRP much earlier and much more intensively than in the absence of TPA. TPA also enhanced stratification of these cultures; however, the positive expression of HRP preceded the stratification. These observations support the view that the induction of terminal differentiation occurs independently of stratification and that the process of terminal differentiation (maturation) of basal cells precedes and triggers the movement of these cells to a suprabasal position (stratification).

Insulin binding and its action in adipocytes of hyperthyroid and hypothyroid rats

The studies of the effects of thyroid hormone on insulin secretion and glucose metabolism have been made, but the results have been controversial. In order to evaluate the effects of thyroid hormone at the cellular level, insulin binding and insulin-induced lipogenesis in isolated rat epididymal fat cells were studied in control, hyperthyroid and hypothyroid rats. Hyperthyroidism was induced by daily intraperitoneal injection of sodium L-thyroxine and hypothyroidism by a single injection of ¹³¹I. The adipocytes were isolated by treatment of collagenase as originally described by Gliemann (1967). The results were as follows: 1) The fasting serum insulin levels of hyperthyroid (21.6 ± 3.7 uU/ml) and hypothyroid groups (20.5 ± 7.0 uU/ml) were not different from the value of control (23.1 ± 11 uU/ml). The fasting blood glucose level of hypothyroid group (164.9 ± 12.0 mg/dl) was higher than the values of the controls (148.2 ± 13.2 mg/dl) or the hyperthyroid group (147.0 ± 12.5 mg/dl), (p<.005). 2) The specific ¹²⁵I-insulin binding of the hyperthyroid group was not different from the value of the controls, but the value of the hypothyroid group was higher than the value of the controls (p<.005). 3) The insulin receptor concentration of the hypothyroid group (1.09 ± 0.02 ng/0.5×10⁵ cells) was higher than the value of the controls (0.72 ± 0.01 ng/0.5×10⁵ cells) or the hyperthyroid group (0.79 ± 0.02 ng/0.5×10⁵ cells), (p<.05). 4) The average affinities of the receptors in all groups showed an inverse correlation with the insulin concentration. The average affinity of the hypothyroid group was higher than the value of the control or the hyperthyroid group. 5) Insulin-induced lipogenesis was reduced proportionately in all insulin concentrations in both the hyperthyroid and hypothyroid groups compared with the dose-response curve of the control group. The maximal amount of lipogenesis of the hyperthyroid and hypothyroid groups were 63.4% (p<.05) and 32.3% (p<.005) of the controls, respectively. These studies suggest that thyroid hormone may regulate the concentration of insulin receptors, and altered thyroid states reduce insulin-induced lipogenesis in the adipocyte at postreceptor levels.

Percutaneous endoscopic gastrostomy for enteral nutrition

From January to October, 1986, at Wonkwang University Hospital in Iri, percutaneous endoscopic gastrostomy(PEG) was attempted in 26 patients and was successful in 24. This study was designed to review the technique and to evaluate the efficacy of PEG. The mean operation time was 22 minutes (range: 14 to 42 minutes). After feeding started, early positive nitrogen balance was achieved in all patients. All gastrostomies functioned well throughout the patient’s survival with the longest functioning at 10 month. There were no procedure-related deaths, and morbidity was lower and less severe as compared with large-bore nasogastric tube feeding. Complications included minor wound infection in two patients, stomal growth in one patient, leaks around the tube in two patients, and intraperitoneal leak in one patient. No patient developed aspiration pneumonia or required laparotomy for complications from PEG. The gastrostomy tube was easily removed endoscopically when treatment was completed. Feeding via a large-bore tube increased the risk of aspiration pneumonia (72%) and the feeding cost via a small-bore tube with elemental diet exceeded that of PEG by more than tenfold. This author’s experience with these 26 patients has led to the conclusion that PEG is safe, easy to perform, and effective means of creating feeding gastrostomy without laparotomy or general anesthesia. The authors suggest that PEG be the preferred route of alimentation in those patients who are unable to swallow for prolonged periods of time.

Morphological change in pancreatic islets, insulin binding and intracellular glucose metabolism in adipocytes of streptozotocin-induced diabetic rats

To examine the diabetogenic mechanism of streptozotocin, a histological study was performed on the pancreatic islets of male Wistar rats 7 days after an intravenous injection of streptozotocin (75 mg/kg). Furthermore, for the investigation into mechanism of insulin resistance in the insulin-dependent diabetic rats, insulin binding, glucose transport, and lipogenesis were studied in the isolated adipocytes of streptozotocin-induced diabetic rats. 1) The rate of weight gain in the control rats and the diabetic rats were 2.2 ± 1.8 g/day and −2.4 ± 2.1 g/day, respectively (p<0.05). The serum insulin levels in the control rats and the diabetic rats were 23.1 ± 10.8 μU/ml and 16.9 ± 10.6 μU/ml respectively (p<0.05). The plasma glucagon levels in the control rats and the diabetic rats were 165.7 ± 124.9 pg/ml. and 151.2 ± 78.2 pg/ml, respectively (p>0.1). 2) Microscopic examination of the pancreatic islets of the diabetic rats revealed a severe degranulation and disintegration of B cells. Electron microscopic examination showed a disruption of the intracytoplasmic organelles of B cells with complete degranulation. But the morphology of A cells was normal. 3) Maximal specific insulin binding to receptors in the adipocytes of the diabetic rats (2.10 ± 0.30%) showed an increase compared with that of the control rats (1.12 ± 0.21 %) (p<0.05). 4) Insulin receptor concentration in the adipocytes of the diabetic rats (2.33 ± 0.43 ng/0.5 × 10⁵ cells) also showed an increase compared with that of control rats (1.03 ± 0.15 ng/0.5 × 10⁵ cells) (p<0.05). 5) The average affinities in the adipocytes of the diabetic rats slightly decreased in the low receptor occupancy state compared with that of the control rats. 6) Basal and insulin-stimulated glucose transports in adipocytes of the diabetic rats decreased compared with that of the control rats. The maximal glucose transport in the adipocytes of the diabetic rats was 31.7% of the control value (p<0.005). 7) Basal and insulin-stimulated lipogenesis in adipocytes of the diabetic rats decreased compared with that of the control rats. The maximal lipogenesis in the adipocytes of the diabetic rats was 38.4% of the control value (p<0.005). It can be concluded that streptozotocin produces a diabetogenic mechanism in Wistar rats by directly injuring the pancreatic B cells and inducing hypoinsulinemia. The insulin resistance in the streptozotocin-induced diabetic rats results from the defects in the intracellular glucose metabolism such as glucose transport and lipogenesis.

Multiple myeloma in Korea--clinical analysis and treatment results in 61 cases

A clinical analysis was made of 61 cases of multiple myeloma diagnosed between January 1976 and June 1984 at Seoul National University Hospital using the criteria of the Southwest Oncology Group.

The following observations were made. 1) The major clinical problems at Initial presentation were bone pain(52%), anemia(20 %), renal impairment(11%), and infection(10%). 2) Clinical stages at presentation were stage I, 11%; stage II, 8%; and stage III, 81% of patients. Three(5%) of the patients in stage II and 18(31%) in stage III showed renal impairment with a serum creatinine ≥2.0 mg/dl. 3) Combination chemotherapy produced a response rate of 29% with melphalan and prednisone, and 40% with M2 protocol(among 14 and 20 evaluable patients respectively). Both regimens showed statistically significant survival difference between responders and non-responders(p <0.01). 4) The median survival of all patients was 13 months. 5)Age, calcium level, creatinine level, and performance status were important prognostic factors on survival.

Renal and renin effects of sodium thiopental in rabbits

Unilateral renal arterial infusion of sodium thiopental on renal function and renin secretion were investigated in unanesthetized rabbits. Sodium thiopental infusion in doses of less than 0.3 mg/kg/min into unilateral renal artery caused dose-dependent increases in urine flow, urinary excretion of electrolytes, fractional excretion of sodium and free water clearance with no changes in systemic blood pressure and clearance of p-aminohippuric acid (renal blood flow). An anesthetic dose of sodium thiopental administered intravenously caused decreases in systemic blood pressure, renal hemodynamics, urine flow and free water clearance during the early period of anesthesia followed by increases in urinary excretion of sodium and fractional excretion of sodium. Unilateral renal arterial infusion of sodium thiopental decreased the renin secretion rate and plasma norepinephrine concentration in renal vein, whereas an anesthetic dose of sodium thiopental administered intravenously increased the renin secretion rate. These observations suggest that the diuretic, natriuretic and renin suppressive effects of sodium thiopental may be due to an inhibition of intrarenal sympathetic nervous system or due to a direct tubular action.

Complex chromosomal abnormalities in a patient with lymphoid blast crisis of chronic myelogenous leukemia

A 46-year-old Chinese man underwent lymphoid blast crisis (Ia+, CALLA+, TdT+) after 5 years of chronic phase, Philadelphia-chromosome positive chronic myelogenous leukemia. Chromosome analysis revealed a hyperdiploid karyotype, including two Philadelphia chromosomes--55,XY,t(9;22) (q34;q11), +2, +5, +5, +6, +10, +18, +19, +21, +del(22)(qll----qter)--in the majority of the leukemic blasts. The constellation of a lymphoid blast crisis and complex chromosomal abnormalities usually associated with myeloid blast crisis as well as the clinical data are discussed.

Erythrocyte Na(+)-K+ ATPase activity in the genesis of reducing renal mass in hypertensive rats

To study the relationship between natriuretic factor and experimental low renin hypertension, the erythrocyte Na⁺-K⁺ ATPase activities in the genesis of reducing renal mass in hypertensive rats were measured. The results were as follows : 1. The fractional excretion of Na in hypertensive, reduced renal mass rats (saline-drinking) was higher than that of normotensive, reduced renal mass rats (water-drinking) (p<.001). The plasma renin activities in the hypertensive group were markedly lower than those of the normotensive group (p<.001). 2. The total ATPase activities of rat erythrocyte membrane in the hypertensive group were lower than in those of the normal and the normotensive groups (p<.001, p<.02). 3. The Mg⁺⁺-ATPase activities of rat erythrocyte membrane in the normotensive group tended to decrease significantly (p<.001), but the differences between the normotensive and hypertensive group were not significant. 4. The Na⁺-K⁺ ATPase activities of rat erythrocyte membrane in the hypertensive group were lower than those of the normal and the normotensive group (p<.001). However, the difference between the normal and the normotensive groups was not significant. 5. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from normotensive rats, the total ATPase activities of erythrocyte membrane were not different from those of hypertensive rats. 6. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from normotensive rats, the Mg⁺⁺ ATPase activities of erythrocyte membrane were lower than those of hypertensive rats (p<.01). 7. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from hypertensive rats, the Na⁺-K⁺ ATPase activities of erythrocyte membrane were lower than those of normotensive rats (p<.01). Based on the above findings, it is suggested that the pathogenesis of low renin, reduced renal mass hypertension is primarily mediated by a natriuretic factor (or an ouabain-like factor, inhibitor of Na⁺-K⁺ ATPase) produced by extracellular fluid volume expansion.

Prenatal diagnosis of a de novo complex chromosomal rearrangement involving four chromosomes

A complex chromosome rearrangement, apparently a balanced translocation involving chromosomes 4, 6, 15 and 16, was found in cultured cells of amniotic fluid from a 32-year-old primigravida who requested amniocentesis for prenatal diagnosis because of a family history of mental retardation. Chromosome analysis of peripheral blood from both parents were normal. The couple was counselled for the prenatal diagnosis of this de novo complex translocation and, subsequently, elected to terminate the pregnancy. Post-mortem examination revealed a 23-week fetus with intrauterine growth retardation. The identical chromosome rearrangement was subsequently confirmed in cultured fibroblasts from skin and cord obtained from the abortus. To our knowledge, this is the first report where routine prenatal diagnosis revealed a fetus with a balanced complex chromosomal rearrangement involving four chromosomes of de novo origin.