Structural requirements for diacylglycerols to mimic tumor-promoting phobol diester action on the epidermal growth factor receptor

The structural requirements for diacylglycerols to mimic the action of tumor-promoting phorbol diesters on the epidermal growth factor (EGF) receptor of A431 human epidermoid carcinoma cells were investigated. Five biological effects were considered: inhibition of high affinity 125I-EGF binding, change in the phosphorylation state of the EGF receptor, inhibition of the EGF-dependent tyrosine phosphorylation of the EGF receptor, inhibition of [3H]phorbol 12 beta, 13 alpha-dibutyrate binding, and stimulation of calcium- and phospholipid-dependent protein kinase (C-kinase) in vitro. A marked effect of the acyl chain length, 3-10 carbons, of symmetric sn-1,2-diacylglycerols was observed on their ability to mimic the effect of 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA). sn-1,2-Dipropanoylglycerol did not mimic the effects of PMA, but sn-1,2-didecanoylglycerol potently mimicked PMA action. A correlation was found between the ability of these diacylglycerols to stimulate the activity of C-kinase in vitro and to mimic the effects of PMA on the EGF receptor in intact cells. Analogues of sn-1,2-dioctanoylglycerol in which the 3' hydroxyl group was substituted with hydrogen, thio or chloro moieties were inactive when assayed for their ability to stimulate C-kinase in vitro and mimic PMA action in intact cells. We conclude that the hydroxyl group of a diacylglycerol is vital for the interaction with the phorbol diester receptor. The stringent correlation between the potency of the 11 diacylglycerol analogues tested to modulate C-kinase in vitro and to mimic PMA action in vivo provides strong evidence for the hypothesis that C-kinase plays a central role in the regulation of A431 cell EGF receptors by tumor-promoting phorbol diesters.     

Application of halophilic nuclease H of Micrococcus varians subsp. halophilus to commercial production of flavoring agent 5'-GMP

RNA was degraded at 60 degrees C for 24 h by halophilic nuclease H in supernatants from broth cultures of Micrococcus varians subsp. halophilus containing 12% NaCl. Since contaminating 5'-nucleotidase exhibited almost no activity under these conditions, the 5'-GMP formed could be recovered from the reaction mixture, and the yield was 805 mg from 5 g of RNA.     

Spatially resolved cytosolic calcium response to angiotensin II and potassium in rat glomerulosa cells measured by digital imaging techniques

The response of cytosolic calcium [Ca2+]i to angiotensin II (AII) and potassium (K+) in individual rat glomerulosa cells was determined using the calcium-sensitive fluorescent dye, fura-2 and digital imaging. Control (4 mM K+) cytosolic calcium levels were generally in the 80-120 nM range and increased monotonically as [K+] was increased from 4 to 12 mM. There was no delay in the onset of the response. In most cells the [Ca2+]i decreased from its peak after 3-4 min, even in the presence of superfusate containing elevated K+. The time course of the change in [Ca2+]i in response to AII stimulation, on the other hand, was more variable. It was most often characterized by an early decrease followed by a large delayed increase. The response also was observed to decline during sustained AII stimulation. The majority of the cells showed some response to one or the other secretagogue with a sizeable minority (25%) having an increase in [Ca2+]i in excess of 200%. While the majority showed a response, the cell to cell variation was substantial. Finally, the pattern of cytosolic calcium increase sometimes showed a marked dependence on the secretagogue used, with different regions of the same cell being more strongly affected by one agent or the other. A few cells (10%) responded to AII only at one pole, establishing a large concentration gradient of calcium across the cell. Because of differences in time course, pattern, and degree of responsiveness, it is likely that the mechanisms underlying the Ca2+ elevation with K+ and AII are different.     

PATTERNS OF REPRODUCTION IN THREE SANDY BEACH WHELKS OF THE GENUS BULLIA GRIFFITH

The breeding cycles of two species of sandy beach whelk (Bulliadigitalis and B. pura) are presented and compared with a thirdspecies (B. rhodostoma). In all three species, egg maturationand copulation occur in spring while summer marks the depositionand spawning of egg capsules. B. digitalis and B. pura migrateoffshore to lay their eggs, the juveniles of both species restrictingthemselves to beyond the breaker zone. Newly hatched snailsof B. rhodostoma appear in the intertidal towards late summer.The discovery of a penis-like structure on females of B. rhodostomais investigated. The pseudopenis was also found on B. pura butnever on B. digitalis. The possibility of a sex-change was eliminatedon the histological investigation of the gonads of a range ofsnails and the examination of sex-ratios over a period of fivemonths. General trends in reproductive behaviour are also discussed. (Received 18 March 1984;     

Controlled trial of methylprednisolone pulses and low dose oral prednisone for the minimal change nephrotic syndrome.

In a multicentre, randomised, prospective trial 89 patients (67 children and 22 adults) with the minimal change nephrotic syndrome were treated with three intravenous pulses of methylprednisolone followed by low dose oral prednisone for six months (group given methylprednisolone) or with high dose oral prednisone for four weeks followed by low dose oral prednisone for five months (control group). Five patients in the group given methylprednisolone and one in the control group did not respond initially. The time to response was shorter in children treated with methylprednisolone. No significant differences between the two groups were observed in the number of patients who relapsed or number of relapses per patient per year. Patients given methylprednisolone tended to relapse earlier than patients in the control group. Side effects related to treatment were significantly fewer in the group given methylprednisolone than in the control group. These data suggest that a short course of methylprednisolone pulses followed by low dose oral prednisone is only marginally less effective than a regimen of high dose oral steroids but can improve the ratio of risk to benefit associated with treatment of the minimal change nephrotic syndrome.     

Monosomy 21: a new case confirmed by in situ hybridization

Summary A new case of total monosomy 21 in a newborn is described. The diagnosis was first made using the cytogenetic data; it was then confirmed by the dosage of copper-superoxide dismutase (SOD-1) which showed a 50% decrease. In situ hybridization with a probe previously assigned to chromosome 21 was used to rule out the possibility of a partial monosomy with an unbalanced reciprocal translocation.     

Development of gastric sensitivity to histamine in the rat

Sensitivity of the developing rat stomach to histamine (HA) was examined on isolated gastric mucosae of rats of various ages from the fetal to adult periods. Spontaneous acid secretion in mu eq/h.cm2 occurred at all the ages studied, at a basal rate of 0.45 +/- 0.07 in fetuses to 0.22 +/- 0.03 (day 5), 0.11 +/- 0.04 (day 10), 0.12 +/- 0.04 (day 12), 0.22 +/- 0.08 (day 16) and 0.33 +/- 0.04 (adults). In the fetal rats as in the adults, marked responses to respectively 10(-5) and 10(-4) M HA were demonstrated. The H2-receptor antagonist cimetidine diminished HA-induced secretion by 66 and 57% in fetuses and adults respectively. Between these two stages (from days 5 to 12), basal secretion and the response to HA dropped significantly. On day 21 of gestation, as well as on the critical days 5 and 12 after parturition, db-cAMP (10(-4) M) caused maximal stimulation of acid secretion. These results indicate that the development of responsiveness to HA in the rat is biphasic. They suggest that after birth, the H2-receptor adenylate cyclase system undergoes major modifications which might lead to the complete lack of responsiveness to HA by day 12.