Properties of phosphatidylinositol kinase activities in rabbit erythrocyte membranes

Properties of phosphatidylinositol kinase activities in rabbit erythrocyte membranes were studied by measuring 32P incorporation into di- and triphosphoinositide from Mg-[gamma-32P]ATP. The Km's for 32P incorporation into di- and triphosphoinositide were 110 and 48 microM ATP, respectively. The optimal temperature for 32P incorporation into diphosphoinositide was at 32 degrees C, whereas the optimum for triphosphoinositide labeling occurred at 43 degrees C. Differences in the effects of pH on the rate of 32P incorporation into di- and triphosphoinositide were also found. At 37 degrees C but not at 25 degrees C 32P-labeled diphosphoinositide was phosphorylated to triphosphoinositide in the presence of Mg-ATP. Triton X-100 partially inhibited 32P incorporation into diphosphoinositide but completely inhibited the synthesis of triphosphoinositide. At physiological concentrations, 0.4 mM MgCl2 half-maximally activated di- and triphosphoinositide synthesis. Higher concentrations of MgCl2 (5 to 50 mM) decreased 32P incorporation into diphosphoinositide and greatly enhanced 32P incorporation into triphosphoinositide. NaCl or KCl (less than or equal to 100 mM) did not have any effects on polyphosphoinositide synthesis, whereas 150 to 300 mM NaCl or KCl decreased synthesis of diphosphoinositide and increased synthesis of triphosphoinositide. Further studies showed that 50 mM MgCl2 and 200 mM NaCl or KCl stimulate kinase-mediated phosphorylation of diphosphoinositide to triphosphoinositide. Triton X-100 inhibited the ability of 50 mM MgCl2 and neomycin to stimulate phosphorylation of diphosphoinositide to triphosphoinositide. The pathways for synthesis of di- and triphosphoinositides in erythrocyte membranes are discussed.     

Re-activation of the peptidyltransferase centre of rabbit reticulocyte ribosomes after inactivation by exposure to low concentrations of magnesium ion.

1. The larger subrivosomal particles of rabbit reticulocytes retained full activity in the puromycin reaction and in poly(U)-directed polyphenylalanine synthesis after 4h at 0 degrees C when buffered 0.5M-NH4Cl/10-30mM-MgCl2 was the solvent. 2. Activity in the puromycin reaction was diminished to approx 10% after 15-30 min at 0 degrees C when the concentration of MgCl2 was lowered to 2mM. 3. Activity was not restored when the concentration of MgCl2 was raised from 2mM to 10-30 mM at 0 degrees C. However, activity was recovered as measured by both assay systems when the ribosome fraction was heated to 37 degrees C at the higher concentrations of MgCl2. 4. Recovery of activity was noted during the course of the polyphenylalanine synthesis in 50 mM-KCl/5mM-MgCl2/25mM-Tris/HCl, pH 7.6, at 37 degrees C. Re-activation was slow at 20 degrees C and below. 5. No more than about 5% of the protein moiety of the subparticle was lost in 0.5M-NH4Cl on decreasing MgCl2 concentration from 10mM to 2mM. No proteins were detected in the supernatant fractions by gel electrophoresis after ribosomes were separated by differential centrifugation. The supernatant fraction was not essential for the recovery of activity. However, at higher (e.g. 1M) concentrations of NH4Cl, proteins were split from the subparticle. 6. The loss and regain of activity found on lowering and restoring the concentration of MgCl2 at 0.5M-NH4Cl appears to arise from a conformational change that does not seem to be associated with a loss and regain of particular proteins. 7. A 2% decrease in E260 was noticed when the concentration of Mg2+ was restored, and the change in the spectrum indicated a net increase of approx. 100A-U base-pairs per subribosomal particle. 8. When the concentration of Mg2+ was restored, S20,W of the subparticle remained at 52+/- 1S until the sample was incubated at 37 degrees C when S20,W increased to 56 +/- 1S compared with the value of 58 +/- 1S for the subparticle as originally isolated.     

Heat-shocked A20 lymphoma cells fail to induce degranulation of cytotoxic T lymphocytes: possible mechanism of resistance

A20 lymphoma cells were subjected to heat shock for 2 h at 42 and 43 +/- 0.1 degrees C and then evaluated at 37 degrees C for sensitivity to lysis by intact allo-specific cytotoxic T lymphocytes (CTLs), perforin-containing granules isolated from CTLs, and Fas-mediated apoptosis. Heat shock at 42 degrees C caused little change in sensitivity of the lymphoma cell line to lysis by intact CTLs or their isolated cytotoxic granules, but caused increased sensitivity to Fas-mediated apoptosis. However, A20 cells shocked at 43 degrees C declined significantly in sensitivity to lysis by intact CTLs, while remaining very sensitive to perforin granules and to Fas-mediated apoptosis. Expression of the inducible heat shock protein was observed in A20 cells incubated at 43 degrees C, but not in those incubated at 42 degrees C, suggesting a role for heat shock proteins. Furthermore, A20 cells shocked at 43 degrees C did not provoke degranulation and secretion of granzymes by antigen-specific CTLs, although formation of CTL-target conjugates and levels of MHC class I molecules remained unchanged. These observations demonstrate that hyperthermia or febrile conditions may reduce susceptibility of target cells to CTL attack due to failure of antigen presentation and the inability of CTLs to recognize heat stressed targets, thus enabling targets to escape CTL attack.     

Plasma membrane Mg(2+)-ATPase of Pachysolen tannophilus: characterization and role in alcohol tolerance.

Following cell fractionation in sucrose density gradients, plasma membrane Mg(2+)-ATPase from Pachysolen tannophilus was studied. The ATPase displayed an apparent Km for ATP of 1.42 mM and was inhibited by high concentrations of Mg2+. The inhibitory effects of ethanol, 1-propanol, 1-butanol, and benzyl alcohol on Mg(2+)-ATPase were evaluated, and the concentration of each alcohol that inhibited ATPase activity by 50% (IC50) was determined. The IC50 decreased as the chain length of the alcohol increased. Moreover, the IC50 for ATPase activity was similar to the IC50 for growth rate, suggesting an association between impaired growth and ATPase inhibition. Almost complete inhibition of ATPase activity occurred at temperatures approaching 60 degrees C, and the optimal temperature was around 44 degrees C for ATPase from both control and ethanol-treated cells. Inclusion of 50 mM MgCl2 or CaCl2 in the medium did not rescue cells from the deleterious effects of ethanol.     

Plasma membrane Mg(2+)-ATPase of Pachysolen tannophilus: characterization and role in alcohol tolerance.

Following cell fractionation in sucrose density gradients, plasma membrane Mg(2+)-ATPase from Pachysolen tannophilus was studied. The ATPase displayed an apparent Km for ATP of 1.42 mM and was inhibited by high concentrations of Mg2+. The inhibitory effects of ethanol, 1-propanol, 1-butanol, and benzyl alcohol on Mg(2+)-ATPase were evaluated, and the concentration of each alcohol that inhibited ATPase activity by 50% (IC50) was determined. The IC50 decreased as the chain length of the alcohol increased. Moreover, the IC50 for ATPase activity was similar to the IC50 for growth rate, suggesting an association between impaired growth and ATPase inhibition. Almost complete inhibition of ATPase activity occurred at temperatures approaching 60 degrees C, and the optimal temperature was around 44 degrees C for ATPase from both control and ethanol-treated cells. Inclusion of 50 mM MgCl2 or CaCl2 in the medium did not rescue cells from the deleterious effects of ethanol.     

Interrelationships and metabolic effects of fatty acids in the perfused rat liver at hyperthermic temperatures

Livers of fasted rats were perfused for 70 min at 37 degrees-43 degrees C in the presence or absence of acetate, octanoate or palmitate. Hepatic biosynthetic capacity was assessed by measuring rates of gluconeogenesis, ureogenesis, ketogenesis and O2 consumption. In the presence of each fatty acid, gluconeogenesis, ureogenesis and oxygen consumption were maintained at 37 degrees and 42 degrees C. At 43 degrees, the rate of glucose formation decreased markedly and rates of ureogenesis and oxygen consumption were distinctly lower. As the temperature was increased from 37 degrees to 43 degrees C without fatty acids, i.e. albumin only, there was a progressive decrease in the rate of gluconeogenesis while the ratio of net C3 utilized to glucose formed, increased successively. The values of this ratio in the presence of palmitate or octanoate at 43 degrees were smaller than those for albumin or acetate, but higher than the figure of 2 for complete conversion of C3 units to glucose. Although fatty acid was added in equimolar amounts of C2 units, total ketone formation was influenced significantly by chain length. Hepatic ketogenesis was similar at 37 degrees with albumin, palmitate, or acetate, but was stimulated significantly by octanoate at 37 degrees and 42 degrees C. At 42 degrees, ketone formation increased in the presence of palmitate. At 43 degrees C, ketogenesis with palmitate or octanoate decreased, while that with acetate or albumin was maintained at the same lower rates. The ratio of 3-hydroxybutyrate to acetoacetate in the perfusate was increased with palmitate at the end of perfusion at 37 degrees and 42 degrees C or octanoate at 42 degrees and 43 degrees C. Thus, long (palmitate)- and medium (octanoate)- but not short (acetate)-chain fatty acids enhance not only beta-oxidation, but influence the redox state of hepatic mitochondria with an increase in the state of reduction of the pyridine nucleotides. Such a shift in the redox state would be operable in the perfused liver even at 43 degrees C and may be responsible for improved conversion of lactate to glucose when medium- or long-chain fatty acids are present at hyperthermic temperatures.     

Effect of incubation temperature on isolation of Campylobacter jejuni genotypes from foodstuffs enriched in Preston broth

Preston broth and agar incubated at either 37 or 42 degrees C have been widely used to isolate campylobacters from foodstuffs. The consequences of using either incubation temperature were investigated. Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased. Samples were incubated in Preston broth at 37 and 42 degrees C and then streaked onto Preston agar and incubated as before. Two Campylobacter isolates per treatment were characterized. Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only. In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters. The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari. The incubation temperature had no significant effect on the number of positive samples or on the species isolated. However, genotyping of the C. jejuni isolates revealed profound differences in the types obtained. Overall (from poultry and lamb), the use of a single incubation temperature, 37 degrees C, gave 56% of the total number of RAPD C. jejuni genotypes, and hence, 44% remained undetected. The effect was especially marked in the poultry samples, where incubation at 37 degrees C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42 degrees C. Thus, the incubation temperature of Preston media selects for certain genotypes of C. jejuni, and to detect the widest range, samples should be incubated at both 37 and 42 degrees C. Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution.     

Involvement of calcium, calmodulin and protein phosphorylation in morphogenesis of Candida albicans

N-Acetyl-D-glucosamine-induced germ tube formation in Candida albicans at 37 degrees C was accompanied by an increase in the rate of protein phosphorylation. The calmodulin antagonist trifluoperazine and the Ca2+ ionophore A23187, which inhibited germ tube formation, also reduced the rate of phosphorylation. The rate of phosphorylation was also reduced when cells were incubated at 25 degrees C, which favoured yeast-phase growth. Two-dimensional SDS-PAGE analysis of phosphoproteins from germ-tube-forming and yeast cells revealed two germ-tube-specific and three yeast-specific phosphoproteins. Germ tubes and hyphae had more calmodulin activity than yeast cells, irrespective of the germ-tube-inducing condition used. As a first step towards understanding the inhibitory effect of trifluoperazine on germ tube formation, calmodulin from C. albicans was purified to homogeneity. It was heat stable, and displayed a pronounced Ca2(+)-induced shift in electrophoretic mobility.     

Effects of hyperthermia on DNA interstrand crosslinking after treatment with BCNU in 9L rat brain tumor cells

The effects of hyperthermia (42 degrees C) on 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU)-mediated DNA interstrand crosslink formation were investigated in 9L rat brain tumor cells using the technique of alkaline elution. When cells were treated with 60 microM BCNU for 1 hr at 37 degrees C and incubated for 6 hr in drug-free medium at 42 degrees C, there was a 50% increase in crosslinking; and when cells were treated at 42 degrees C and incubated at 37 degrees C, there was a 45% increase in crosslinking compared with the results for cells treated and incubated at 37 degrees C. When cells were treated and incubated at 42 degrees C, there was a 129% increase in DNA crosslinking. The same relative order of results was found for cell survival. These results suggest that hyperthermia can increase DNA interstrand crosslink formation and the consequent cell death through two independent mechanisms: an increase in the amount of initial alkylation because of the increased rate of hydrolysis of BCNU at higher temperatures, and the effect of heat on DNA structure that leads to an increase in the number of crosslinks formed.     

Effect of puparia incubation temperature: increased infection rates of Trypanosoma congolense in Glossina morsitans centralis, G.fuscipes fuscipes and G.brevipalpis

Puparia of Glossina morsitans centralis (Machado), G.fuscipes fuscipes (Newstead) and G.brevipalpis (Newstead) were incubated at 25 +/- 1 degrees C, 28 +/- 1:25 +/- 1 degrees C, day:night or 29 +/- 1 degrees C throughout the puparial period, and maintained at 70-80% relative humidity. Puparial mortality was higher at 29 than at 25 degrees C (optimum temperature) in all three species, particularly in G.f.fuscipes and G.brevipalpis. Adults of G.m.centralis from puparia incubated at 29 degrees C, and those of this subspecies, G.f.fuscipes and G.brevipalpis from puparia incubated at 28:25 degrees C, day:night or 25 degrees C throughout, were infected as tenerals (27 h old) by feeding them at the same time on goats infected with Trypanosoma congolense (Broden) IL 1180 after the parasites were detected in the wet blood film. Infection rates on day 25 post-infected feed were higher in G.m.centralis from puparia incubated at 29 degrees C and in adults of the three different tsetse species from puparia incubated at 28:25 degrees C, day:night, than in those from puparia incubated at 25 degrees C. However, in G.f.fuscipes the labral and hypopharyngeal infection rates were not significantly different from those of the tsetse produced by puparia kept at 25 degrees C.     

Synthesis of bacteriophage phiC DNA in dna mutants of Esherichia coli.

Host dna functions involved in the replication of microvirid phage phiC DNA were investigated in vivo. Although growth of this phage was markedly inhibited even at 35-37 degrees C even in dna+ host, conversion of the infecting single-stranded DNA into the double-stranded parental replicative form (stage I synthesis) occurred normally at 43 degrees C in dna+, dnaA, dnaB, dnaC(D), and dnaE cells. In dnaG mutant, the stage I synthesis was severely inhibited at 43 degrees C but not at 30 degrees C. The stage I replication of phiC DNA was clearly thermosensitive in dnaZ cells incubated in nutrient broth. In Tris-casamino acids-glucose medium, however, the dnaZ mutant sufficiently supported synthesis of the parental replicative form. At 43 degrees C, synthesis of the progeny replicative form DNA (stage II replication) was significantly inhibited even in dna+ cells and was nearly completely blocked in dnaB or dnaC(D) mutant. At 37 degrees C, the stage II replication proceeded normally in dna+ bacteria.     

Inhibition of the ATPase activity of Escherichia coli ATP synthase by magnesium fluoride

Inhibition of ATPase activity of Escherichia coli ATP synthase by magnesium fluoride (MgFx) was studied. Wild-type F(1)-ATPase was inhibited potently, albeit slowly, when incubated with MgCl(2), NaF, and NaADP. The combination of all three components was required. Reactivation of ATPase activity, after removal of unbound ligands, occurred with half-time of approximately 14 h at 22 degrees C and was quasi-irreversible at 4 degrees C. Mutant F(1)-ATPases, in which catalytic site residues involved in transition state formation were modified, were found to be resistant to inhibition by MgFx. The data demonstrate that MgFx in combination with MgADP behaves as a tight-binding transition state analog in E. coli ATP synthase.     

Effects of limited tryptic cleavage on the physical and enzymatic properties of myosin II from Acanthamoeba castellanii

Limited digestion of Acanthamoeba myosin II by trypsin selectively cleaved the 185,000-Da heavy chains into a 73,000-Da peptide containing the catalytic and actin-binding sites and a 112,000-Da peptide containing the regulatory phosphorylatable sites. The light chains were unaffected. The proteolytic products remained associated and formed bipolar filaments that were very similar in appearance to filaments of native myosin by negative staining electron microscopy. Filaments of trypsin-cleaved, dephosphorylated myosin, however, had a smaller sedimentation coefficient than filaments of native dephosphorylated myosin. Trypsin-cleaved dephosphorylated myosin retained complete Ca2+-ATPase activity but had no actin-activated ATPase activity under conditions that are optimal for native, dephosphorylated myosin (pH 7.0, 4 mM MgCl2, 30 degrees C or pH 6.4, 1 mM MgCl2, 30 degrees C). Trypsin-cleaved dephosphorylated myosin had higher actin-activated ATPase activity at pH 6.0 and 1 mM MgCl2 than undigested dephosphorylated myosin which is appreciably inhibited under these conditions. Trypsin-cleaved, dephosphorylated myosin inhibited the actin-activated ATPase activity of native, dephosphorylated myosin when both were present in the same co-polymers, when enzymatic activity was assayed at pH 7.0, 4 mM MgCl2, and 30 degrees C, but this inhibition was overcome by raising the MgCl2 to 6 mM. These results provide additional evidence that regulation of acanthamoeba myosin II occurs at the filament level and that, under most conditions of assay, the heavy chains must be intact and the regulatory serines unphosphorylated for actin-activated ATPase activity to be maximally expressed.     

Comparison of Muller-Kauffmann tetrathionate broth with Rappaport-Vassiliadis (RV) medium for the isolation of salmonellas from sewage sludge

The Rappaport-Vassiliadis (RV, modification of Rappaport's) medium was superior to Muller-Kauffmann tetrathionate broth (MKT) for the enrichment and isolation of salmonellas from sewage sludge samples, either naturally contaminated or artificially inoculated with salmonella. Isolation rates for RV (42 degrees C) were higher even when MKT (43 degrees C) performance was improved by the use of brilliant green sul-phamandelate agar. Kinetic results show that the suppression of the competing flora was poorer in MKT than in RV. The use of high inoculum to medium volume ratios (e.g. 1:5000) increased the isolation rates from RV and kinetic data explain why this was so.     

Control of total peripheral resistance during hyperthermia in rats

To elucidate the effect of blood volume on the circulatory adjustment to heat stress, we studied alpha-chloralose-anesthetized rats at three levels of blood volume: normovolemia (NBV), hypervolemia (HBV; +32% plasma volume by isotonic albumin solution infusion), and hypovolemia (LBV; -16% plasma volume by furosemide administration). Body surface heating was performed with an infrared lamp to raise arterial blood temperature (Tb) at the rate of approximately 0.1 degree C/min. Before heating, central venous pressure (CVP) was significantly higher in HBV (0.41 +/- 0.25 mmHg) and lower in LBV (-1.44 +/- 0.22 mmHg) than in NBV (-0.41 +/- 0.10 mmHg). The Tb at which CVP started to decrease was approximately 40 degrees C in HBV, approximately 41 degrees C in NBV, and approximately 42 degrees C in LBV, and it decreased by 1.53 +/- 0.14, 1.92 +/- 0.24, and 0.62 +/- 0.14 mmHg from 37 to 43 degrees C of Tb in HBV, NBV, and LBV, respectively. Stroke volume was closely correlated with CVP, and this relationship was not affected by Tb. Heart rate responses to the raised Tb were similar among the three groups. Mean arterial pressure (MAP) was not affected by blood volume modification or CVP and was maintained at preheating (Tb 37 degrees C) level until Tb rose to 40 degrees C. Above this Tb, MAP increased until Tb reached 43 degrees C (+30-40 mmHg) for all three groups. Total peripheral resistance (TPR) was inversely correlated with CVP, and the slope of the linear relationship between TPR and CVP in LBV was three- to fourfold steeper than in NBV or HBV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of deferoxamine methanesulfonate on Trichophyton mentagrophytes.

Deferoxamine methanesulfonate (Desferal), an iron chelator, inhibited germ tube formation and growth of Trichophyton mentagrophytes in a microculture assay. A 50% reduction of germ tube formation required Desferal at 5 mg/ml and a 50% reduction of growth required 1.5 mg/ml. Growth was almost completely inhibited with 50 and 100 mg/ml. Also, Desferal at 100 mg/ml inhibited further elongation when added to short hyphae (II and 21 micrometer), but showed less inhibitory effects when added to long hyphae (64 micrometer). Iron (133 microgram/ml) reversed the inhibition of growth produced by incubating spores with Desferal at 5 mg/ml, providing iron was added before 72 h incubation. Desferal at 100 mg/ml decreased viability of activated spores incubated for 3 days at 30 degrees C, but did not decrease viability of spores incubated for 3 days at 4 degrees C. The growth inhibitory effect of Desferal and transferrin were compared. Transferrin was inhibitory at low molarities (0.001 to 1.0 mM), while Desferal was inhibitory only at higher molarities (greater than 1 mM). Desferal (0.05 mM) also reversed the inhibition expected with 0.05 mM transferrin. These findings indicate that Desferal and transferrin deprive T. mentagrophytes of nutritional iron and thus inhibit growth of the fungus. Low concentrations of Desferal can also promote growth in the presence of transferrin.     

Effect of high temperature and water stress on in vitro germination and growth in isolates of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin

In non-irrigated agricultural fields in tropical zones, high temperature and water stress prevail during the main cropping season. Natural epizootics of Beauveria bassiana on lepidopteran pests occur during winter. Application of B. bassiana during hot months when pest populations are at their climax may prove an effective management strategy. Therefore, 29 isolates of B. bassiana were tested for their ability to germinate and grow in temperature and water availability conditions prevailing during the pest season in these fields. The effect of temperature cycles with 8 h duration of high temperature fluctuating with 16 h duration of lower temperature (similar to field conditions); low water availability; and a combination of these two stress conditions was studied. Germination and growth assays were done at fluctuating temperature cycles of 32, 35, 38, and 42+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and in media with water stress created by 10, 20, 30, and 40% polyethylene glycol (PEG 6000). Assays set at a continuous temperature of 25+/-1 degrees C with no PEG in the medium served as controls. Stress was assessed as percentage germination or as growth relative to control. Isolates showing 90% growth relative to the control at temperature cycles including high temperatures of 35 and 38+/-1 degrees C were identified. One isolate (ARSEF 2860) had a thermal threshold above 43 degrees C. At 25 degrees C, all but one isolate of B. bassiana showed >90% growth relative to the control in 10% PEG (-0.45 MPa). Some isolates were found with >90% growth relative to control in medium having 30% PEG with water availability (1.33 MPa), nearly equivalent to that in soils which induce permanent wilting point of plants. When isolates that showed >90% growth relative to the control at both stress conditions, were stressed simultaneously, a decrease in growth was observed. Growth was reduced by approximately 20% at 35+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG and was affected to a greater degree in combinations of harsher stress conditions. The isolate ARSEF 2860 with a thermal threshold of >43 degrees C showed approximately 80% relative growth at a combined stress of 38+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG. These findings will aid the selection of isolates for use in field trials in hot or dry agricultural climates.     

Requirement of Cyclic Adenosine 3′,5′-Monophosphate for the Thermosensitive Effects of Rts1 in a Cyclic Adenosine 3′,5′-Monophosphate-Less Mutant of Escherichia coli

Previous publications showed that a covalently closed circular (CCC) Rts1 plasmid deoxyribonucleic acid (DNA) that confers kanamycin resistance upon the host bacteria inhibits host growth at 42 degrees C but not at 32 degrees C. At 42 degrees C, the CCC Rts1 DNA is not formed, and cells without plasmids emerge. To investigate the possible role of cyclic adenosine 3',5'-monophosphate (cAMP) in the action of Rts1 on host bacteria, Rts1 was placed in an Escherichia coli mutant (CA7902) that lacks adenylate cyclase or in E. coli PP47 (a mutant lacking cAMP receptor protein). Rts1 did not exert the thermosensitive effect on these cells, and CCC Rts1 DNA was formed even at 42 degrees C. Upon addition of cAMP to E. coli CA7902(Rts1), cell growth and formation of CCC Rts1 DNA were inhibited at 42 degrees C. The addition of cAMP to E. coli PP47(Rts1) did not cause inhibitory effects on either cell growth or CCC Rts1 DNA formation at 42 degrees C. The inhibitory effect of cAMP on E. coli CA7902(Rts1) is specific to this cyclic nucleotide, and other cyclic nucleotides such as cyclic guanosine 3',5'-monophosphate did not have the effect. For this inhibitory effect, cells have to be preincubated with cAMP; the presence of cAMP at the time of CCC Rts1 DNA formation is not enough for the inhibitory effect. If the cells are preincubated with cAMP, one can remove cAMP during the [(3)H]thymidine pulse and still observe its inhibitory effect on the formation of CCC Rts1 DNA. The presence of chloramphenicol during this preincubation period abolished the inhibitory effect of cAMP. These observations suggest that cAMP is necessary to induce synthesis of a protein that inhibits CCC Rts1 DNA formation and cell growth at 42 degrees C.     

Effect of temperature and humidity on development, survival and oviposition in laboratory populations of Eriworm, Philosamia ricini (Boisduval) (Lepidoptera Saturniidae)

Experiments were conducted on laboratory populations of Eriworm, Philosamia ricini Boisduval to study the effect of temperature and humidity on development, growth, survival and oviposition. Experiments were performed at four different temperatures (22 +/- 2 degrees C, 26 +/- 2 degrees C, 28 +/- 2 degrees C and 34 +/- 1 degrees C) each with three different humidities (50%, 70% and 90% relative humidity). Shortest developmental period (42 days) was observed in 28 +/- 2 degrees C and 70% RH. Longest developmental period was (63.6 days) observed in 22 +/- 2 degrees C at 50% RH. Highest larval weight (9.1 g) was found in 28 +/- 2 degrees C at 70% RH. Best pupal weight was observed in 26 +/- 2 degrees C at 70% RH. Weight of silk material was found to be maximum in 26 +/- 2 degrees C at 70% RH. Survival was best in 28 +/- 2 degrees C and 26 +/- 2 degrees C at 70% RH. Oviposition was found to be highest in 28 +/- 2 degrees C at 70% RH.