A new cholescintigraphic agent: Ruthenium-97-DISIDA

These are the first human experiments with ⁹⁷Ru-DISIDA, a potentially new alternative to ¹³¹I-rose bengal where delayed imaging is indicated. ⁹⁷Ru has a convenient half life. A DISIDA labeling kit was utilized to prepare the radiotracer for 17 patients (age 6 weeks-84 years). The Cholescintigraphic data correlated well with other imaging procedures and with clinical findings. Dosimetric calculations were carried out and were compared with the radiation burden associated with the use of ^99mTc-DISIDA and ¹³¹I-rose bengal.     

Radionuclide cholescintigraphic imaging: An evaluation of several 99mTc labelled hepatobiliary radiopharmaceuticals

Recently, much interest has been shown in the development of ^99mTc labelled Cholescintigraphic agents for imaging the hepatobiliary tract. In this study six Cholescintigraphic agents were compared in rabbits with respect to (a) transit efficiency through the liver and (b) the halftime on the washout portion of the liver time-activity curve. The agents compared were P-butyl-IDA (PBIDA), diisopropyl-IDA (DISIDA), two mebrofenin (MBF) agents and two pyridoxylaminates (PDA). Best transit efficiencies were obtained with MBF (34.1 and 31.2%) followed by PDA (27.7 and 24.9%) while DISIDA (23.0%) and PBIDA (19.3%) were the lowest. The same phenomenon was observed regarding the washout halftime, with MBF the most rapid (6.3 and 5.9 min), PDA more prolonged (10.1 and 12.0 min) and DISIDA and PBIDA the slowest (23.0 and 23.2 min). This study confirms the difference in physiological behaviour of the various Cholescintigraphic agents and shows identical flow patterns for locally produced and imported compounds.     

The use of clove oil to induce anaesthesia,and its effects on blood chemistry,in Lates niloticus from Lake Victoria,Uganda

The efficacy of clove oil as an anaesthetic and its effects on blood parameters in Nile perch Lates niloticus were evaluated in 2010. Clove oil concentrations of 49.3, 73.9 and 98.5?mg l^?1 induced anaesthesia in <3?min, while the average recovery time from anaesthesia was 11?min 22 s. The optimal oil clove oil concentration was 49.3?mg l^?1, inducing anaesthesia in 4?min 33 s, with recovery in 3?min 31 s. No stress response was elicited. Clove oil at a concentration of 24.6?mg l^?1 was an effective sedative, whereas a concentration of 49.3?mg l^?1 was sufficient for measuring fish and stripping gametes. A concentration of 73.9?mg l^?1 induced anaesthesia within 4?min and fish recovered in 10?min. Therefore, clove oil was an effective anaesthetic and sedative for the handling of Nile perch within a mass range of 0.4–12?kg fish^?1.     

Turnover of coniferin in pine seedlings

Coniferin (coniferyl alcohol-β-d-glucoside) was not detected in pine seeds (Picea abies) but it accumulated in the stems and roots of pine seedlings. Pulse labeling experiments with l-phenylalanine-[U-¹⁴C] and 100-day-old pine seedlings in hydroponic solution showed a turnover of coniferin with a half life of about 60 hr. Pulse labeling with ¹⁴CO₂ and seedlings kept in soil gave a half life of about 120 hr for coniferin. The results indicate that coniferin could be an intermediate of lignin biosynthesis in pine seedlings.     

Chronology of chromosome reduplication in Chinese hamster cells incubated at low temperature

Experiments have been carried out on Chinese hamster fibroblasts. Cultures at the log-stage of growth were incubated at 15 or 25° C for 24 hrs. In two groups of experiments the cells were labeled with H³-TdR for 6 hrs at the respective temperature, washed and further incubated at 37° C. In each group of experiments cultures labeled with H³-TdR at 37° C for 20 min were used as a control. It was found: 1. the delay in the onset of cell passage through the mitotic cycle at 37° in cultures exposed to 15 or 25° C was about equal to 1,5-1 hr resp. and cells proceeded through the life cycle without blockages at any phase of the cycle; 2. the patterns of chromosome reproduction during the second half of the S-phase were the same after labeling at 15, 25 and 37° C. — In the third group the cells were labelled with HP-TdR for 10–60 min and 6 hrs resp. at 25° C. The patterns of reproduction of chromosome pairs 1–4 and small metacentrics were found to be the same in cells labeled briefly and those labeled for 6 hrs. After brief labeling asynchronous reduplication of different segments in many chromosomes became evident. It was masked because of heavy labeling after 6 hrs treatment.     

Optimal rates of 2,4‐dichlophenoxyacetic acid foliar application for control of common scab in potato

Applications of the synthetic auxin 2,4‐dichlorophenoxyacetic acid (2,4‐D) to the foliage of potato plants can reduce common scab, a tuber disease. However, in prior research effective applications at 200 mg L^?1 2,4‐D resulted in phytotoxic side effects with reduced tuber yield and quality. This study showed that minimal significant threshold rates from 8.3 to 23.6 mg L^?1 2,4‐D reduced disease incidence in pot trials, and from 10.8 to 41.0 mg L^?1 minimised disease severity in both pot and field trials. In only one pot trial, significant phytotoxicity was found with rates of 100 mg L^?1 or greater, reducing mean total tuber mass per plot and 38 mg L^?1 or greater, reducing mean mass per tuber. Notably, within the field trial, a more reliable plant growth system for estimation of yield, no significant impacts were observed. Disease control was associated with decreased sensitivity of tubers to thaxtomin A, the phytotoxin produced by the common scab pathogen essential for disease induction. The amount of residual 2,4‐D in tubers at harvest varied with cultivar, Russet Burbank accumulating more 2,4‐D than Desiree. Application rates less than 100 mg L^?1 resulted in levels of 2,4‐D below the Australian standard maximum residue limit. These data suggest that applications of 2,4‐D at low rates could provide a commercially suitable control strategy for common scab.     

ATP-dependent calcium transport and its correlation with Ca2+-ATPase activity in basolateral plasma membranes of rat duodenum

Isolated basolateral plasmamembrane vesicles from rat duodenum epithelial cells exhibit ATP-dependent calcium-accumulation and Ca²⁺-dependent ATPase activity. Calcium accumulation stimulated by ATP is prevented by the calcium ionophore A23187, inhibited 80% by 0.1 mM orthovanadate but is not effected by oligomycin. Calcium accumulation is not observed with the substrate β-γ-(CH₂)-ATP, ADP and p-nitrophenyl phosphate. Kinetic studies reveal an apparent K_m of 0.2 μM Ca²⁺ and a V_max of 5.3 nmol Ca²⁺/min per mg protein for the ATP-dependent calcium-uptake system. Calmodulin and phenothiazines have no effect on calcium accumulation in freshly prepared membranes, but small effects are inducable after a wash with a 5 mM EGTA. The kinetic parameters of Ca²⁺-ATPase are: K_m = 0.25 μM Ca²⁺ and V_max = 19.2 nmol P_i/min per mg protein. Three techniques, osmotic shock, treatment with Triton X-100 or the channel-forming peptide alamethacin, reveal that about 40% of the vesicles are resealed. Assuming that half of the resealed vesicles have an inside-out orientation, the V_max of ATP-dependent calcium uptake amounts to 25 nmol Ca²⁺/min per mg protein and of the Ca²⁺-ATPase to 23 nmol P_i/min per mg protein. The close correlation between kinetic parameters of Ca²⁺-ATPase and ATP-dependent calcium-transport strongly suggests that both systems are expressions of a Ca²⁺-pump located in duodenal basolateral plasma membranes.     

Metabolism of 3H- and 14C-labelled lactate in starved rats

1. [2-³H,U-¹⁴C]- or [3-³H,U-¹⁴C]-Lactate was administered by infusion or bolus injection to overnight-starved rats. Tracer lactate was injected or infused through indwelling cannulas into the aorta and blood was sampled from the vena cava (A–VC mode), or it was administered into the vena cava and sampled from the aorta (V–A mode). Sampling was continued after infusion was terminated to obtain the wash-out curves for the tracer. The activities of lactate, glucose, amino acids and water were followed. 2. The kinetics of labelled lactate in the two modes differed markedly, but the kinetics of labelled glucose were much the same irrespective of mode. 3. The kinetics of ³H-labelled lactate differed markedly from those for [U-¹⁴C]lactate. Isotopic steady state was attained in less than 1h of infusion of [³H]lactate but required over 6h for [U-¹⁴C]lactate. 4. ³H from [2-³H]lactate labels glucose more extensive than does that from [3-³H]lactate. [3-³H]Lactate also labels plasma amino acids. The distribution of ³H in glucose was determined. 5. Maximal radioactivity in ³HOH in plasma is attained in less than 1min after injection. Near-maximal radioactivity in [¹⁴C]glucose and [³H]glucose is attained within 2–3min after injection. 6. The apparent replacement rates for lactate were calculated from the areas under the specific-radioactivity curves or plateau specific radioactivities after primed infusion. Results calculated from bolus injection and infusion agreed closely. The apparent replacement rate for [³H]lactate from the A–VC mode averaged about 16mg/min per kg body wt. and that in the V–A mode about 8.5mg/min per kg body wt. The apparent rates for [¹⁴C]lactate (`rate of irreversible disposal') were 8mg/min per kg body wt. for the A–VC mode and 5.5mg/min per kg body wt. for the V–A mode. Apparent recycling of lactate carbon was 55–60% according to the A–VC mode and 35% according to the V–A mode. 7. The specific radioactivities of [U-¹⁴C]glucose at isotopic steady state were 55% and 45% that of [U-¹⁴C]lactate in the A–VC and V–A modes respectively. We calculated, correcting for the dilution of ¹⁴C in gluconeogenesis via oxaloacetate, that over 70% of newly synthesized glucose was derived from circulating lactate. 8. Recycling of ³H between lactate and glucose was evaluated. It has no significant effect on the calculation of the replacement rate, but affects considerably the areas under the wash-out curves for both [2-³H]- and [3-³H]-lactate, and calculation of mean transit time and total lactate mass in the body. Corrected for recycling, in the A–VC mode the mean transit time is about 3min, the lactate mass about 50mg/kg body wt. and the lactate space about 65% of body space. The V–A mode yields a mass and lactate space about half those with the A–VC mode. 9. The area under the wash-out curve for [¹⁴C]lactate is some 20–30 times that for [³H]lactate, and apparent carbon mass is 400–500mg/kg body wt. and presumably includes the carbon of glucose, pyruvate and amino acids, which are exchanging rapidly with that of lactate.     

Labeling deoxyribonucleic acid to high specific activity in vitro by nick translation with DNA polymerase I

Circular (e.g. simian virus 40) and linear (e.g. λ phage) DNAs have been labeled to high specific radioactivities (>10⁸ cts/min per μg) in vitro using deoxynucleoside [α-³²P]triphosphates (100 to 250 Ci/mmol) as substrates and the nick translation activity of Escherichia coli DNA polymerase I. The reaction product yields single-stranded fragments about 400 nucleotides long following denaturation. Because restriction fragments derived from different regions of the nick-translated DNA have nearly the same specific radioactivity (cts/min per 10[su3] bases), we infer that nicks are introduced, and nick translation is initiated, with equal probability within all internal regions of the DNA. Such labeled DNAs (and restriction endonuclease fragments derived from them) are useful probes for detecting rare homologous sequences by in situ hybridization and reassociation kinetic analysis.     

Effect of Escherichia coli endotoxin on adenine nucleotide translocation in canine heart mitochondria

The in vitro effect of Escherichia coli endotoxin on the translocation of adenine nucleotides in dog heart mitochondria was studied. Mitochondrial adenine nucleotides were labeled with ¹⁴C by incubating mitochondrial preparations in the presence of [¹⁴C]ADP. The exchange reaction was initiated by addition of unlabeled ADP, proceeded for 5 to 60 s at 4 °C, and was terminated by addition of atractyloside. The results showed that preincubation of mitochondria with endotoxin (50 μg/mg protein) for 10 min at 23 °C decreased the exchange reaction by 21.2% (P < 0.05). The inhibitory effect of endotoxin was increased with increasing concentrations of endotoxin with an I₅₀ value of 45 μg/mg protein. The initial rate and the total extent of exchange were both affected. Double reciprocal plots showed that only the V but not the K_m for ADP was affected by endotoxin, indicating that the inhibition was noncompetitive in nature. The exchange of adenine nucleotide remained depressed by endotoxin in the presence of either oligomycin or antimycin A, indicating that the inhibitory effect of endotoxin was independent of the action of endotoxin on oxidative phosphorylation. The leakage of labeled adenine nucleotides from mitochondria at 23 °C was increased by 100% by endotoxin (100 μg/mg protein) in the absence of added unlabeled ADP, and this increase in the leakage could not be blocked by atractyloside. The endotoxin-induced changes in adenine nucleotide exchange and leakage were either partially or completely prevented by hydrocortisone, heparin, dibucaine, or EDTA. Since most of these agents have in common an effect on lipid metabolism, it is suggested that endotoxin-induced alterations in the exchange and leakage of adenine nucleotides in heart mitochondria are protected through a mechanism involving membrane lipid reorganization.     

A microdialysis study of allatostatin degradation in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Allatostatins with a typical C‐terminal sequence YXFGL‐NH₂ are insect neuropeptides with inhibitory properties upon Juvenile Hormone production in the corpora allata, vitellogenin release by the fat body, and gut and dorsal vessel motility. All these biological effects are rapidly reversible, suggesting the occurrence of effective mechanisms for inactivation of the peptides. We have studied the degradation of DRLYSFGL‐NH₂ (BLAST‐2), one of the allatostatins of Blattella germanica, in the internal milieu of adult females of this cockroach. The experimental approach combined the use of the radioiodinated derivative [¹²⁵I‐Tyr⁴]BLAST‐2, microdialysis techniques and HPLC analysis with a radioisotope detector. Under these experimental conditions, the half‐life of BLAST‐2 in the internal milieu of the adult female of B. germanica was between 3 and 6 min. Such a short half‐life explains the high doses of allatostatins required to obtain the expected biological effects when tested in vivo, and suggests that circulating allatostatins are subject to rapid rates of synthesis and degradation in order to be operative physiologically.     

<Superscript>177</Superscript>Lu-DOTA-coupled minigastrin peptides: promising theranostic agents in neuroendocrine cancers

Treatment with radionuclide labeled regulatory peptides is a promising tool in the management of patients with inoperable receptor positive neuroendocrine tumors. Peptide receptor lutetium-177 radionuclide therapy currently has gained ample attention due to high specific accumulation of regulatory peptides at tumor cell surface and promising characteristics of β- and γ-energy photons of lutetium-177 radionuclide. In this study gastrin peptides analogues were labeled with lutetium-177 by subsequent mixing of ¹⁷⁷LuCl₃ (~?185 MBq), ammonium acetate buffer of 5 pH, gentistic acid, aqueous solution of gastrin peptide analogues (1 mg/mL) and heating the reaction mixture at 98 °C which resulted in high radiochemical yield (>?96%). Chromatographic analysis was carried out to analyze the radiochemical purity. The shelf life and serum stability results showed the labeled peptides are sufficiently stable up to 4-h. Glomerular filtration rate study results showed moderate filtration through kidneys. The GFR values of ¹⁷⁷Lu-MGCL2 and ¹⁷⁷Lu-MGCL4 was noted 48 mL/min and 45 mL/min, respectively. Biodistribution and scintigraphy study using rat and rabbit models showed minimal non-target accumulation, moderate uptake by liver and kidneys. The promising radiochemical yield, stability, GFR values and biodistribution results of ¹⁷⁷Lu-MGCL2 & 4 indicate, the agents can be tested clinically for PRRT procedures.     

Effects of HNS-32, a novel antiarrhythmic drug,on ventricular arrhythmias induced by coronary artery occlusion and reperfusion in anesthetized rats

HNS-32 (N¹,N¹-dimethyl-N²-(2-pyridylmethyl)-5-isopropyl-3, 8-dimethylazulene-1-carboxamidine: CAS 186086-10-2) is a newly synthesized compound, and possesses antiarrhythmic properties with vasodilator action in dog hearts. The aim of this study was to investigate the dose-dependent effects of HNS-32 on ischemia- and/or reperfusion-induced ventricular arrhythmias in anesthetized rats in vivo and compared with those of mexiletine. Saline or drugs were administered intravenously 5 min prior to coronary artery occlusion. On the ischemia-induced ventricular arrhythmias, HNS-32 showed dose-dependent reduction of total number of premature ventricular complexes (PVC) from 2091 ± 225 to 656 ± 116 and 286 ± 69 beats/30 min (p < 0.05), the ventricular tachycardia (VT) duration from 183 ± 33 to 28 ± 9 and 4 ± 2 sec (p < 0.05), the incidence of VT from 100 to 90 (n.s.) and 40% (p < 0.05), and the incidence of ventricular fibrillation (VF) from 50 to 0 and 0% (p < 0.05) with 3 and 5 mg/kg, respectively. Mexiletine also reduced these parameters to 936 ± 159 beats/30 min (p < 0.05), 39 ± 22 sec (p < 0.05), 90% (n.s.) and 10% (n.s.), respectively. HNS-32 completely suppressed the late reperfusion-induced arrhythmias, however mexiletine did not affect them. On the early reperfusion-induced ventricular arrhythmias, HNS-32 showed dose-dependent reduction of VT duration from 126 ± 34 to 37 ± 12 and 3 ± 2 sec (p < 0.05), incidence of VT from 100 to 90 (n.s.) and 40% (p < 0.05), incidence of VF from 100 to 10 and 0% (p < 0.05), and mortality rate from 90 to 0 and 0% (p < 0.05), with 3 and 5 mg/kg, respectively. Mexiletine also reduced these parameters to 16 ± 9 sec (p < 0.05), 80 (n.s.), 50 (p < 0.05), and 10% (p < 0.05), respectively. HNS-32 significantly reduced the heart rate in a dose-dependent manner, from 399 ± 14 to 350 ± 8 and 299 ± 10 beats/min (p < 0.05) with 3 and 5 mg/kg, respectively. The antiarrhythmic effects of HNS-32 were more potent than that of the similar dose of mexiletine against occlusion-induced and reperfusion-induced arrhythmias in in vivo rats.     

Sucralfate delays gastric emptying of liquids and solids in duodenal ulcer patients

Gastric emptying studies were performed on nine healthy volunteers and ten duodenal ulcer (DU) patients utilizing a dual radionuclide technique to assess simultaneously emptying rates of liquid (¹¹¹In labeled water) and solid (^99mTc sulfur colloid labeled chicken liver) components of a meal. One gram of sucralfate was compared to placebo in separate days in a randomized double-blind crossover fashion. Subjects ingested the radiolabeled test meal 1 h after receiving medication, and gastric emptying was monitored for 3 h using a γ camera interfaced with a computer. We found that DU patients had significantly faster gastric emptying of solids (P < 0.05) compared to normals on the placebo days, while liquid emptying rates were similar. Sucralfate, in the DU patients, significantly (P < 0.05) slowed gastric emptying of water from 20 to 40 min and emptying of the solid component from 100–160 min after the meal compared to placebo. In normal subjects, gastric emptying of liquids and solids was not significantly affected by sucralfate.We conclude that slowing of gastric emptying, possibly mediated through aluminum ions, occurs in DU patients on sucralfate. This may be one mechanism by which sucralfate enhances healing and decreases recurrence of duodenal ulcer.     

Feasibility study of fluorine-18 labeled dopa for melanoma imaging

Feasibility of fluorine-18 labeled l-dopa for melanoma imaging was investigated. In B16 melanoma-bearing mice given 2-[¹⁸F]fluoro-l-dopa, the radioactivity in the B16 decreased for the first 60 min and then remained constant, while all other tissues investigated decreased with time. High tumor uptake ratios for all other tissues except for the pancreas were obtained at 120 min. 6-[¹⁸F]Fluoro-l-dopa showed a similar tissue distribution. However, the B16 uptake was about half that value for the 2-fluoro analogue. A higher incorporation rate of 2-[¹⁸F]fluoro-l-dopa into the acid-precipitable fraction of the melanoma also showed that the 2-[¹⁸F]fluoro-l-dopa was a preferable melanin precursor. Among the four kinds of non-melanoma tumors in mice or rats three tumors showed an uptake of 2-[¹⁸F]fluoro-l-dopa similar to the B16 at 60 min. However, larger melanoma-to-tissue uptake ratios were observed when compared to non-melanoma tumors.     

Increased PC-1 phosphodiesterase activity and inhibition of glucose uptake in adipocytes of type 2 diabetic rats

This study was designed to understand the cellular mechanisms responsible for defects in the insulin-stimulated signal transduction pathway in a type 2 diabetic animal model. We examined the in vitro PC-1 phosphodiesterase activity and glucose uptake in adipose tissue of streptozotocin (STZ)-induced type 2 diabetic rats. The PC-1 activity was significantly increased in adipose tissue of diabetic rats (0.54 ± 0.08 nmol PNTP hydrolyzed/mg protein/min) compared with controls (0.29 ± 0.05 nmol PNTP hydrolyzed/mg protein/min, p < 0.05). Upon insulin stimulation (100 nM), glucose uptake in the adipose tissue of the controls (4.17 ± 1.28×10⁻⁸ μmol/mg/min) was significantly higher than that in the diabetic rats (1.26 ± 0.35×10⁻⁸; p < 0.05). These results suggest that elevated PC-1 phosphodiesterase activity and decreased glucose uptake in adipose tissues may be acquired characteristics contributing to the development of type 2 diabetes mellitus.     

Effective immobilizing doses of medetomidine-ketamine in free-ranging, wild Norwegian reindeer (Rangifer tarandus tarandus)

Combinations of medetomidine and ketamine were evaluated in free-ranging, wild Norwegian reindeer (Rangifer tarandus tarandus) as part of a reintroduction program in southwestern Norway in November 1995 and November 1996. The drugs were administered by dart from a helicopter. The mean (SD) effective immobilizing doses for 29 adults (8 males, 21 females) were 0.21 (0.04) mg medetomidine/kg and 1.0 (0.2) mg ketamine/ kg based on estimated body mass. There was no significant difference in mean induction times between males and females. However, animals with optimal hits (shoulder or thigh muscles; n=16) had a significantly shorter (P<0.05) mean induction time than did animals with suboptimal hits (abdomen or flank; n=13), 5.6 (2.2) min and 11.1 (4.7) min, respectively. Inductions were calm, and immobilized animals were maintained in sternal recumbency. Clinical side effects included hypoxemia and hyperthermia in most animals. For reversal, all animals received 5 mg atipamezole per mg medetomidine, half intravenously and half intramuscularly, and the mean (SD) time to standing was 3.7 (3.6) min.     

Metabolic activation of hexamethylmelamine and pentamethylmelamine by liver microsomal preparations

Incubation of [¹⁴C]-ring labeled hexamethylmelamine and pentamethylmelamine with rat and mouse liver microsomal preparations results in metabolic activation of both drugs as measured by covalent binding of radiolabel to acid-precipitable microsomal macromolecules. Covalent binding is dependent on viable microsomes, NADPH, and molecular oxygen. Binding of HMM (280 pmol/mg protein/15 min) was approximately 5 times greater than that observed for PMM (60 pmol/mg protein/15 min), and represents 0.22% of incubated material. Similar results were found with [¹⁴C]-methyl labeled substrates. Pretreatment with phenobarbital increased covalent binding while addition of SKF 525-A, addition of glutathione, or incubation in an 80% carbon monoxide atmosphere reduced covalent binding.     

Biosorption of nickel (II) from effluent of electroplating industry by immobilized cells of Bacillus species

In this study, Ni (II) biosorption capacity of immobilized cells of Bacillus sp. was investigated. Biosorption of Ni (II) was carried out in batch experiments and the important environmental conditions were optimized. The uptake of metal was rapid, and equilibrium was attained within 270 min. Bacillus strains (ten cultures) were isolated from nickel electroplating effluent by heat shock method. These isolates were grown up in nutrient broth supplemented with Ni (II)(50 mg/L). The culture, exhibiting maximum biosorption capacity (q^max: 118 mg/g), was selected and labeled Bacillus Bio‐4. In order to develop an economical biosorption process cell mass of Bacillus, Bio‐4 was immobilized in Na‐alginate. It was concluded from the results that biosorption of nickel is highly dependent on the type of sorbent and experimental conditions employed. Our results demonstrate that 6.0 mg immobilized cells (18 mg cell biomass in 3.0 mL of 1% Na alginate) had a maximum biosorption capacity of 113 mg Ni(II) per liter of suspension at pH 8.0, 100 rpm and 25°C. The Ni (II) removal was estimated to be 97.4%.     

Polyphosphoinositide synthesis in rabbit erythrocyte membranes

Incubation of rabbit erythrocyte ghosts at 25 °C with 1 mm [γ-³²P]ATP and MgCl₂ results in incorporation of ³²P into diphosphoinositide and triphosphoinositide with initial rates of 15.6 and 1.8 nmol ³²P/mg/h, respectively. Incorporation of ³²P into diphosphoinositide plateaus after 20 min whereas incorporation into triphosphoinositide did not plateau until after 80 min. Diphosphoinositide and triphosphoinositide, prelabeled with ³²P, did not undergo significant breakdown when incubated at 25 °C for 15 to 20 min. Turnover of ³²P-labeled diphosphoinositide and triphosphoinositide was insignificant in the presence of MgCl₂ and cold ATP. Diphosphoinositide is not phosphorylated to triphosphoinositide in the presence of Mg-ATP under conditions in which synthesis of these polyphosphoinositides can occur. In the presence of neomycin and Mg-ATP, labeled diphosphoinositide was rapidly phosphorylated to triphosphoinositide. Neomycin had no effect on labeled di- and triphosphoinositide content in the absence of ATP. Freeze-thawing the ghosts or the addition of Triton X-100 does not produce the same effect as neomycin. The results of this investigation suggest that diphosphoinositide and triphosphoinositide are normally synthesized from endogenous phosphatidylinositol in rabbit ghosts by separate enzymatic pathways. Neomycin an aminoglycoside which interacts with polyphosphoinositides may perturb the organization of substrates and kinase activities involved in polyphosphoinositide metabolism and alter these pathways.