Involvement of protein kinase(s) in the intracellular signal transduction pathways for activation and adaptation of adenylate cyclase in Dictyostelium discoideum

Binding of cyclic AMP (cAMP) to cell surface receptors induces activation and adaptation of adenylate cyclase while 2,3-dimercapto-1-propanol (BAL) acts only on the activation pathway. Here we show that an inhibitor of protein kinase (K252a) inhibits the cAMP-induced activation of the cyclase but not (rather enhances) the BAL-induced activation. These results suggest that protein kinase is involved in transduction of the activation signal and that phosphorylation might take place between the receptor and the action site of BAL. Since adaptation causes cessation of the activation, the enhancement of the BAL-induced cAMP accumulation by K252a might imply that K252a also blocks transduction of the adaptation signal.

Suppression of tyrocidine production by purine nucleotides and related substances in Bacillus brevis

Bacillus brevis (ATCC 8185) produces an antibiotic peptide, tyrocidine. We found that adenosine or 5'-AMP suppressed the production of tyrocidine with half-maximum inhibition at 100-300 microM. This inhibition was specific to the production of tyrocidine since neither adenosine nor 5'-AMP showed any effect on bacterial growth. Cyclic nucleotides had no effect. These results suggest that adenosine, 5'-AMP or its metabolite was specifically involved in the regulation of tyrocidine production.

[Clinical significance of red cell distribution width in polycythemia vera]

We evaluated changes in red cell distribution width-standard deviation (RDW-SD) measured using a multiple parameter automated hematology analyzer E 4000 in patients with polycythemia vera (PV). Patients with iron deficiency anemia, those with chronic myelogenous leukemia, those with primary thrombocythemia, and normal subjects were examined as controls. In the patients with PV, as in those with the other 3 diseases, RDW-SD tended to be higher than in the normal controls when red blood cell counts were high. The RDW-SD in patients with PV transiently increased following administration of a myelosuppressive, which corresponded to the transition period from microcytes to normal blood cells. It was even higher during the polycythemic period than during the myelofibrotic period. This may be associated with hematopoietic abnormality due to extramedullary hematopoiesis. RDW-SD seems to well reflect the pathologic status of PV.

Role of cyclic AMP and ammonia in induction and maintenance of post-aggregative differentiation in a suspension culture of Dictyostelium discoideum

The effects of ammonia and cAMP on prespore and prestalk differentiation of Dictyostelium discoideum were investigated by monitoring eight developmentally regulated proteins as differentiation markers under the shake culture conditions in glucose/albumin medium. In the medium containing cAMP, cells form small agglomerates and undergo prespore differentiation [19]. Under the conditions where agglomeration was prevented, ammonia induced four marker proteins out of eight tested in the presence of cAMP, which included not only a prespore specific enzyme but also cell-type non-specific proteins. No inhibitory effect of ammonia was observed in presumptive cell differentiation. These results suggest that ammonia is an inducer of differentiation at the protein level as well as the mRNA level as found previously [24]. The effects of cAMP were examined with special attention to the difference between induction of differentiation and maintenance of differentiated state in this specific medium. The induction of differentiation from early aggregative cells was cAMP-dependent with all the marker proteins tested. This agrees with the observations so far obtained in other culture systems. However, when already differentiated cell masses (slugs) were dissociated and shaken in this specific medium, only two enzymes required cAMP to maintain the activity while five out of eight kinds of the proteins continued to be expressed as in undisturbed slugs even without cAMP. This suggests that for the maintenance of the differentiated state after slug disaggregation cAMP may not be required with respect to the majority of proteins, if cells are provided with some favorable conditions such as glucose/albumin medium.

Changes during differentiation in requirements for cAMP for expression of cell-type-specific mRNAs in the cellular slime mold, Dictyostelium discoideum

A number of genes encoding developmentally regulated mRNAs in the cellular slime mold, Dictyostelium discoideum, have been described. Many of these are regulated by cAMP. Analysis of the earliest time at which elevated levels of cAMP can induce the expression of these mRNAs reveals a more complex pattern of regulation in which genes change in their ability to be induced in response to cAMP with developmental stage. A prestalk mRNA (C1/D11) previously thought not be regulated by elevated levels of cAMP is inducible by cAMP between aggregation and loose mound stage; later in development its expression becomes independent of elevated cAMP. The early prespore genes (prespore class I) also show two modes of regulation; early in development they are induced independently of continuous elevated levels of cAMP, while later in development their expression is dependent upon elevated cAMP. The period during development when the prestalk genes are cAMP inducible precedes by 2 hr the first time at which either the early prespore class I or late prespore class II mRNAs are inducible by continuous elevated levels of cAMP. Previous analysis of these mRNAs has been carried out using Dictyostelium cells grown axenically. In this report we have studied the developmental expression of these mRNAs in cells grown on bacteria. A substantial shutoff of the class I prestalk and early prespore (class I) mRNAs not seen in axenically grown cells is observed when bacterially grown cells are plated for development. Less than 10% of the maximal level of these mRNAs remains in the cells at the time of mature spore and stalk differentiation. Additionally, in the bacterially grown cells two distinct patterns of developmental regulation are observed for mRNAs which in axenically growing cells appear to be constitutively expressed throughout growth and development.

Cyclic AMP and NH3/NH4+ both regulate cell-type-specific mRNA accumulation in the cellular slime mold, Dictyostelium discoideum

Dictyostelium discoideum cells plated for development until aggregation stage, and then dissociated into media containing glucose, albumin, and cAMP will form into clumps and undergo prespore and prestalk differentiation. Differentiation in this in vitro system is dependent on three components: cAMP, multicellularity, and the acquisition of "differentiation competence" which the cells acquire in a period between interphase and aggregation stage when plated on Millipore filters. We have used this system to explore aspects of the multicellular environment which are involved in regulation the accumulation of the different prespore- and prestalk-specific messenger RNAs. Two classes of prespore messenger RNA, as well as a prestalk-specific messenger RNA, all require the acquisition of differentiation competence in order to be expressed in response to cAMP. Additionally, all of these messenger RNAs require agglomerate formation for maximal expression. The addition of 33 mM ammonium sulfate (NH4)2SO4, however, can entirely replace the requirement for agglomerate formation for expression of the prestalk-specific messenger RNA, and can partially substitute for agglomerate formation in inducing the expression of both classes of prespore-specific messenger RNAs. In this system, cAMP is essential for the initial induction of expression of all three classes of messenger RNAs. In this system, cAMP is essential for the initial induction of expression of all three classes of messenger RNAs while agglomerate formation or elevated NH3/NH+4 is essential only for the maintenance of the elevated levels of the messenger RNAs.

Interaction of cAMP with the cell-surface receptor induces cell-type-specific mRNA accumulation in Dictyostelium discoideum

The accumulation of many postaggregative mRNA species in Dictyostelium discoideum is dependent upon the continuous presence of elevated levels of cAMP. We have analyzed the cyclic nucleotide specificity of this requirement and show that it is similar to that of the cell-surface receptor and distinct from the specificity displayed by the cAMP-dependent protein kinase. The same specificity is displayed for the accumulation of two classes of prespore mRNAs (class I, early; class II, late) and a prestalk mRNA and for the shutoff of a growth-phase mRNA. Under conditions in which cAMP phosphodiesterase activity is competitively inhibited, half-maximal accumulation of prestalk mRNA can be obtained at cAMP concentrations of 320-520 nM, whereas a higher concentration, 1-2 microM, is required for half-maximal accumulation of the prespore mRNAs and shutoff of the growth-phase mRNA. These effects of cAMP and its analogues on gene expression have been obtained under conditions in which cAMP-mediated activation of adenylate cyclase is completely inhibited. We conclude that cAMP acts to stimulate postaggregative gene expression by interacting at the cell-surface receptor.

Characterization of free radical-mediated damage of canine cardiac sarcoplasmic reticulum

In vitro generation of free radicals by xanthine oxidase acting on xanthine as substrate depressed steady-state calcium uptake by canine cardiac sarcoplasmic reticulum vesicles. The effect of free radicals on the calcium-dependent ATPase activity of the SR vesicles was pH dependent. At pH 7.0, ATPase activity was decreased, but at pH 6.4 it was unchanged. Exposure to free radicals increased the passive permeability of the vesicles to calcium. This increase was inhibited by superoxide dismutase (SOD) at pH 7.0, and SOD plus mannitol at pH 6.4. The increased permeability per se was insufficient to explain the effects of free radicals on ATPase activity, since the calcium ionophore A23187 was unable to mimick these effects. Direct measurement of the number and turnover of the pump units indicated that the number of units was unchanged but turnover was decreased by free radicals at pH 7.0. The overall data suggest at least two mechanisms of free radical damage, one associated with an increase in passive permeability and another associated with an as yet undefined change in some specific steps of the ATPase reaction.

Proportion regulation without pattern formation in Dictyostelium discoideum

When shaken in a glucose-albumin-cAMP medium, dissociated aggregative cells formed small clumps, in which both prespore and prestalk cells differentiated in essentially the same proportions as in a slug. Immunocytochemical staining of sections of such clumps revealed that the two types of cells showed no particular pattern of distribution, unlike the two-zoned prestalk-prespore pattern as observed in the slug. Cells dissociated at stages later than the onset of aggregation always produced a constant proportion of prespore cells, irrespective of the initial proportion when transferred to the culture. Furthermore, prestalk cells fractionated from slugs and transferred to the culture restored almost the normal prespore protortion through conversion of the cell types, whereas proportion of unfractionated slug cells remained unchanged. We conclude from these findings that the normal prestalk-prespore pattern is not required for proportion to be regulated.

The effects of thoracic aortic cross-clamping and declamping on visceral organ blood flow

Blood flow was measured using radioactive microspheres in 11 macaque monkeys 1) before hemorrhage shock, 2) after onset of shock, 3) after aortic cross-clamping and resuscitation, and 4) after release of the cross-clamp and stabilization. Hemodynamic parameters (cardiac output, arterial, right atrial and left atrial pressure) and blood gases were also monitored. Total abdominal organ flow fell with hemorrhage and fell further with aortic clamping. Reinfusion of shed volume did not restore abdominal organ flow (4.7% baselines) but increased LAP and cardiac output to the upper body. Release of the cross-clamp produced profound acidosis that was treated effectively with NcHCO3. After stabilization of blood, flow to kidney remained low (49% baseline) although intestinal flow was increased threefold (320% of baseline). It is clear that thoracic aortic cross-clamping in shock further compromises already reduced visceral blood flow and may contribute to the problem of ischemic multiple organ failure after resuscitation from hemorrhagic shock.

Anaphylaxis-induced increase in plasma cyclic AMP dependent on endogenous catecholamines in rats

Plasma cyclic AMP levels during anaphylactic shock in rats was studied in 7 groups of animals: (1) control rats; (2) rats with adrenomedullectomy; (3) rats treated with propranolol; (4) rats with reserpinization; (5) rats with 6-hydroxydopamine-induced chemical sympathectomy; (6) rats treated with hexamethonium, and (7) rats treated with cocaine (catecholamine uptake inhibitor). All experiments were carried out in ovalbumin-sensitized rats. Plasma cyclic AMP showed a rapid increase during anaphylactic shock in control rats. Adrenomedullectomy abolished the anaphylaxis-induced increase in plasma cyclic AMP, while hexamethonium had no effect. Propranolol caused a dose-dependent abolition of the increase. The treatment of rats with reserpine, 6-hydroxydopamine or cocaine partially inhibited the increase in plasma cyclic AMP. The results show that the adrenal medulla is the major source of catecholamines during anaphylactic shock, and that catecholamines in the adrenergic neuronal terminals may be partly responsible for the anaphylaxis-induced increase in plasma cyclic AMP.

Effects of cyclic AMP on contact formation and differentiation in Dictyostelium discoideum

It has been shown previously that Dictyostelium discoideum NC4 cells dissociated at the early aggregation stage form cell clumps and differentiate into prespore cells in a shaking culture containing glucose, albumin, EDTA and cyclic AMP. In this culture system, we found that the cells neither differentiate nor form cell clumps in the absence of cyclic AMP. Wheat-germ agglutinin (WGA) completely inhibited the cyclic AMP-induced formation of cell contact and the inhibition was nullified by the addition of N-acetyl-D-glucosamine. When the cells were prevented from forming contact by either rapid shaking or the addition of WGA, they were unable to differentiate even in the presence of cyclic AMP, indicating that contact formation is a prerequisite for prespore differentiation. Cells dissociated from migrating slugs formed cell clumps in shaking culture, with or without cyclic AMP, and the cell contact was sensitive to WGA. In the absence of cyclic AMP, prespore cells lost their differentiated state, even though the cells were in contact. This indicates that cyclic AMP has a second effect, that of pomoting differentiation, in addition to the effect of inducing contact formation. Both effects were required for prespore differentiation of strain NC4 cells.

Comparison of three different assays for the assessment of ciguatoxin in fish tissues: radioimmunoassay, mouse bioassay and in vitro guinea pig atrium assay

Moderate correlation was shown between the following tests: RIA: mouse bioassay (r = 0.58); RIA: guinea pig atrium assay (r = 0.62); guinea pig atrium assay: mouse bioassay (r = 0.62). All three assay procedures showed good correlation when ciguatoxin was present in tissues in high concentrations. The results also suggest that more than one structurally related toxin may be present in the fish tissues.

Free radical damage to sarcoplasmic reticulum of masseter muscle by arachidonic acid and prostaglandin G2

In vitro generation of free radicals by xanthine oxidase acting on hypoxanthine as a substrate induced a decreased calcium uptake velocity and reduced calcium-dependent ATPase activity of isolated sarcoplasmic reticulum (SR) vesicles from canine masseter muscle at pH 7.0. At pH 5.5 calcium uptake velocity was also reduced but ATPase activity was unaffected. Application of arachidonic acid or prostaglandin G2 induced the depression of both calcium uptake velocity and ATPase activity. The effect of arachidonic acid and prostaglandin G2 on ATPase activity depended on the pH. At pH 7.0, ATPase activity was decreased, but at pH 5.5 it was unchanged. These effects were reversed by superoxide dismutase (SOD) at pH 7.0, and by SOD plus mannitol at pH 5.5. Prostaglandin H2, prostaglandin E2 and 11,14,17-eicosatrienoic acid had no effect on calcium uptake velocity and ATPase activity at both pH 7.0 and pH 5.5. These results suggest that damage to the masseter muscle is caused by a free radical superoxide anion generated as a result of increased prostaglandins synthesis, and by the production of more lethal hydroxyl radical switched from the production of superoxide anion at low pH.

Congenital inclusion dermoid cyst of the anterior fontanel in a Japanese infant: case report

We report an 8-month-old Japanese female infant with a congenital inclusion dermoid cyst of the anterior fontanel. At operation it was located beneath the pericranium. The analysis of the fluid contents of the cyst and the histological findings are described.

Prostaglandin E2 and cyclic nucleotides during anaphylactic shock in rats

Anaphylactic shock was induced with ovalbumin in sensitized rats and the relationship between PGE2 and cyclic nucleotides in lung tissue and plasma histamine during anaphylactic shock was studied. PGE2 level and cyclic AMP/cyclic GMP ratio decreased with this ovalbumin-challenge, and the former reached a minimum value 40 sec after the challenge while the latter reached a minimum value 20 sec later. The plasma histamine level was elevated and reached a maximum value concomitant with the minimum value in the cyclic AMP/cyclic GMP ratio. Dibutyryl cyclic AMP elevated the PGE2 level significantly and inhibited the ovalbumin-induced elevation of plasma histamine, however, this effect was abolished by the administration of indomethacin. PGE2 infusion elevated the cyclic AMP level as well as the cyclic AMP/cyclic GMP ratio, in a time-dependent manner, and inhibited the ovalbumin-induced elevation of plasma histamine during 10 min infusion. There was a significant correlation between the cyclic AMP level and the cyclic AMP/cyclic GMP ratio, both elevated by PGE2 infusion. Thus, anaphylactic elevation of the plasma histamine level results from a decrease in the levels of PGE2 in lung tissue rather than a decrease in the cyclic AMP/cyclic GMP ratio, albeit these decreases being coincident during anaphylactic shock.