Interaction of myasthenic serum globulin with the acetylcholine receptor.

A serum factor from patients with myasthenia gravis which inhibited the binding of 125I-labeled alpha-bungarotoxin to acetylcholine receptor extracted with Triton X-100 from rat muscle has been studied in detail. The inhibitory activity was localized to the IgG fraction based upon the fractionations by sodium sulfate precipitation and DEAE chromatography as well as reaction with anti-IgG globulin. The myasthenic globulin inhibited toxin binding to receptors extracted from degenerated muscle but did not inhibit toxin binding to normal junctional receptors. At saturation levels of myasthenic globulin, the number of denervated acetylcholine receptors available for toxin binding was reduced approx. 50 percent. The myastehnic globulin was found to bind to denervated acetylcholine receptors but not to normal acetylcholine receptors by a radioimmunoassay technique in which myasthenic globulin incubated with 125I-labeled alpha bungarotoxin-receptor complexes was precipitated by anti-IgG serum. The globulin binding was saturable over the same range as inhibition of toxin binding. The data suggest that the myasthenic IgC binds to a site on the receptor complex juxtaposed to the acetylcholine receptor site. The myasthenic globulin appears to be a useful probe for investigation differences between acetylcholine receptors extracted from normal and denervated muscle and for investigating the pathogenesis of myasthenia gravis.     

Cholinergic sites in skeletal muscle. I. Denervation effects.

Cholinergic interactions in systems derived from rat skeletal mixed muscle are detailed. The isotherms of the binding of [125I]diiodo-alpha-bungarotoxin over the range of 10(-10)-10(-5) M toxin have been separated into a "nonspecific" component exclusive to the toxin and a "specific" component that binds both the toxin and d-tubocurarine. The "specific" component appears to reflect two independent sets of binding sites. One of the sets has an affinity constant on the order of 10(9) M-1. Following denervation, the number of sites in this high-affinity set begins to increase after 3 days, reaches a peak (28-fold higher than normal) on the 8th day, and begins to decline. Similar results are obtained when sensitivity of this set to an antibody derived from patients with myasthenia gravis is examined. This sensitivity is reflected by the inhibition of the alpha-bungarotoxin binding by the myasthenic IgG fraction. Following denervation, sensitivity first appears on day 3 progresses coincidentally with the increase in new sites in the set. The charcteristics of this set suggest that it represents the acetylcholine receptor and that the new sites appearing during the course of denervation are extrajunctional receptor sites. The interaction with the myasthenic IgG indicates an antigenic difference between junctional and extrajunctional receptors. The second set of specific binding sites has an affinity constant on the order of 10(5) M-1. The number of sites in this set increases only fivefold as a result of denervation. The increase also begins between days 2 and 3. The definition of this low affinity set of sites is not presently clear.     

ACETYLCHOLINE RECEPTORS: NUMBER and DISTRIBUTION IN INTACT and DEAFFERENTED SUPERIOR CERVICAL GANGLION OF THE RAT1

Abstract— α-Bungarotoxin (α-BuTX) has been used as a marker for studying the acetylcholine receptors (AChRs) in the superior cervical ganglion (SCG) of the adult rat. Binding of [¹²⁵I]α-BuTX to detergent-solubilized AChRs from rat SCG is a saturable and practically irreversible process. The rate constant of association of the toxin-receptor complex is 1.66 × 10⁵M ^?1 S^?1. The receptor is of nicotinic type. One SCG of adult rat binds about 57 fmol of [¹²⁵I]α-BuTX corresponding to 9.2 × 10⁵ AChRs per sympathetic neuron. Light microscope autoradiography shows that AChRs are mainly localized along neuronal processes (probably dendrites). The perikarya exhibit a weak radioactive reaction, while the nerve fibres are devoid of AChRs. Following preganglionic denervation the number of AChRs never increases and their spatial distribution seems not to change.     

Fc gamma receptors on rat eosinophils: isotype-dependent cell activation

Fc receptors for rat IgG subclasses (IgG2a, IgG2c, and IgG1) were studied on rat eosinophils by rosette formation with erythrocytes coated with monoclonal immunoglobulin (Ig) or anti-Ig antisera in a reverse assay. Inhibition experiments revealed that IgG2a and IgG2c bind to the same receptor (IgG2a/IgG2c Fc receptor), distinct from the receptor for IgG1. In addition to the recent demonstration of the blocking effect of IgG2c antibodies in immunity to schistosomes, the present results show that the existence of this common receptor led to the specific inhibition by IgG2c of IgG2a-mediated eosinophil peroxidase release. Kinetic experiments on Schistosoma mansoni-infected rat eosinophils indicate that the IgG2a/IgG2c Fc receptors were occupied by cytophilic antibodies of the IgG2a isotype during the early phase of infection and by IgG2c thereafter. By rosette experiments it was possible to displace both in vivo and in vitro cytophilically bound IgG2a from its receptor. These results confirm, therefore, the major role played by antibodies in the modulation of eosinophil effector function during schistosomiasis. They underline, moreover, the possible isotypic regulation of cell activation.     

Antibodies to muscarinic acetylcholine receptors in myasthenia gravis

IgG obtained from patients with myasthenia gravis block the specific binding of the muscarinic antagonists (³H)-N-methyl-4-piperidyl benzilate (4NMPB) and (³H)-Quinuclidinyl benzilate to rat brain muscarinic acetylcholine receptors. IgG obtained from healthy controls have a much smaller effect. The inhibitory effect of the myasthenic IgG increases linearly with immunoglobulin concentration and has no effect on the affinity of the muscarinic receptors towards (³H)-4NMPB (K_D = 0.7 ± 0.1 nM). This implies that the inhibition is probably due to the blocking of some of the muscarinic receptors by the myasthenic IgG, and not due to alteration in affinity of all the receptors. it remains to be established whether the presence of antimuscarinic receptor activity in the serum of myasthenic patients is of importance in the pathophysiology and diagnosis of myasthenia gravis.     

A Cys-loop mutation in the Caenorhabditis elegans nicotinic receptor subunit UNC-63 impairs but does not abolish channel function

The nematode Caenorhabditis elegans is an established model organism for studying neurobiology. UNC-63 is a C. elegans nicotinic acetylcholine receptor (nAChR) α-subunit. It is an essential component of the levamisole-sensitive muscle nAChR (L-nAChR) and therefore plays an important role in cholinergic transmission at the nematode neuromuscular junction. Here, we show that worms with the unc-63(x26) allele, with its αC151Y mutation disrupting the Cys-loop, have deficient muscle function reflected by impaired swimming (thrashing). Single-channel recordings from cultured muscle cells from the mutant strain showed a 100-fold reduced frequency of opening events and shorter channel openings of L-nAChRs compared with those of wild-type worms. Anti-UNC-63 antibody staining in both cultured adult muscle and embryonic cells showed that L-nAChRs were expressed at similar levels in the mutant and wild-type cells, suggesting that the functional changes in the receptor, rather than changes in expression, are the predominant effect of the mutation. The kinetic changes mimic those reported in patients with fast-channel congenital myasthenic syndromes. We show that pyridostigmine bromide and 3,4-diaminopyridine, which are drugs used to treat fast-channel congenital myasthenic syndromes, partially rescued the motility defect seen in unc-63(x26). The C. elegans unc-63(x26) mutant may therefore offer a useful model to assist in the development of therapies for syndromes produced by altered function of human nAChRs.     

Biochemical and genetic analysis of variant C of caprine αs2-casein (Capra hircus)

Two alleles, A and B, were previously described at the goat α_s2-casein locus. Isoelectric focusing allowed us to subdivide the former one in two new alleles, called A and C. Although α_s2-casein C cannot actually be distinguished from its A counterpart by starch or polyacrylamide gel electrophoresis, it differs from the previous allele by a single substitution Lys (A)/Ile (C) at position 167, which was confirmed at the nucleotide level. The frequencies of the three α_s2-casein alleles A, B and C were estimated to be 0.85, 0.04 and 0.11 in the French dairy breeds ‘Alpine’ and ‘Saanen’.     

Serum concentrations of MCP-1 and IL-6 in combination predict the presence of coronary artery disease and mortality in subjects undergoing coronary angiography

The UBA–UBX domain-containing proteins can interact with ubiquitinated substrates and p97 during endoplasmic reticulum-associated degradation (ERAD). Here, we found that the expressions of all UBA–UBX genes p47, SAKS1, UBXD8, FAF1, and UBXD7 were elevated upon ER stress, albeit with different levels. Of which p47, SAKS1, and UBXD8 are ‘immediate’ respondents whereas FAF1 and UBXD7 were ‘late’ respondents to ER stress. Interestingly, the expression of specific UBA–UBX genes were altered in cells stably expressing three different ERAD substrates such as α-TCR, α1-antitrypsin, and δCD3. We first found that p47 and UBXD8 expression levels were increased in α-TCR and α1-antitrypsin stable cell lines, respectively, whereas SAKS1 expression level was reduced in all the three ERAD substrates tested. Of note, we also found p47 promotes, whereas SASK1 delays the degradation of a single ERAD substrate, α-TCR. Additionally, we found that SAKS1 selectively inhibits the degradation of ERAD substrates without affecting cytosolic proteasomal substrates. Taken together, our results identified that UBA–UBX proteins possess substrate selectivity and opposite role of two different UBA–UBX proteins in the degradation of a single ERAD substrate.     

Estimates of quantal content during 'chemical potentiation' of transmitter release.

The number of quantal transmitter packets (m), released from motor nerve terminals in response to a single stimulus, has been estimated from the ratio of the amplitudes of endplate currents (e.p.c.) to spontaneous miniature endplate currents (m.e.p.c.), in voltage-clamped endplates of the frog. At 6 degrees C, the average value of m at normal nerve-muscle junctions was about 300. If allowance is made for the temporal dispersion of quantal transmitter release during the e.p.c., this value is increased by about 30%. After treatment with diaminopyridine or tetraethylammonium, transmitter release in response to a nerve stimulus is greatly enhanced and values of m exceeding 10(4) are frequently found. Moreover, the duration of the e.p.c. becomes much longer than that of the m.e.p.cs. The number of packets then liberated during the e.p.c. is much larger than the number of 'active zones' of the endplate and may even exceed the total number of vesicles lined up in twin-files adjacent to the presynaptic membrane.     

Some magnetic properties of Pseudomonas cytochrome oxidase.

The magnetic properties of the haem groups of Pseudomonas cytochrome oxidase and its cyanide-bound derivatives were studied in both the oxidized and reduced states by means of m.c.d. (magnetic circular dichroism) at low temperatures. In addition, the oxidized forms of the enzyme were also investigated by e.p.r. (electron-paramagnetic-resonance) spectroscopy, and a parallel study, using both e.p.r. and m.c.d., was made on Pseudomonas cytochrome c-551 to aid spectral assignments. For ascorbate-reduced Pseudomonas cytochrome oxidase, the temperature-independence of those features in the m.c.d. spectrum corresponding to the haem c, and the temperature-dependence of those signals corresponding to the haem d1, showed the former to be low-spin and the latter to be high-spin (s = 2). However, addition of cyanide to the reduced enzyme gave a form of the protein that was completely low-spin. The e.p.r. and m.c.d. sectra of oxidized Pseudomonas cytochrome oxidase and its cyanide derivative were consistent with the haem c and d1 components being low-spin in both cases. Pseudomonas cytochrome c-551 was found to be low-spin in both its oxidized and reduced redox states.     

Optimisation of the transmit beam parameters for generation of subharmonic signals in native and altered populations of a commercial microbubble contrast agent SonoVue®

The aim of this work was to establish the optimum acoustic characterisation approach and insonation transmit beam parameters for subharmonic signal generation with ‘native’ and ‘altered’ populations of a commonly-used microbubble contrast agent. Dynamic contrast-enhanced (DCE) ultrasound is a non-invasive method of imaging the microvasculature, typically implemented using harmonic imaging. Subharmonic imaging, in which echoes at half the fundamental frequency are detected, detects signals which are generated by the ultrasound contrast agents (UCAs) but not by tissue. However, optimal transmission parameters and furthermore, the optimum acoustic characterisation method have not been established. The subharmonic response of ‘native’ and ‘altered’ UCA, altered through decantation, was investigated at transmit centre frequencies 1.8–5 MHz and pulse lengths 1–8 cycles. The ‘altered’ UCA had reduced polydispersity (1–4 µm: 82% bubble volume), compared to ‘native’ (4–10 µm: 57% bubble volume). A custom-built narrow-band acoustic characterisation system was found to be more appropriate for acoustic characterisation compared to the commonly used broadband pulse-echo approach. Both UCA generated the highest subharmonic signal at pulse length of 3-cycles. The maximum ‘native’ subharmonic signal was generated at a transmit centre frequency of 1.9 MHz, corresponding to a subharmonic at 0.95 MHz. This optimal frequency increased in the ‘altered’ population to 2.3–2.5 MHz, bringing the subharmonic above 1 MHz and hence into a range amenable to clinical abdominal imaging transducers. The use of subharmonic signal detection coupled with a modified UCA size distribution has potential to significantly improve the quantification sensitivity and accuracy of DCE ultrasound imaging.     

部分中国传统月季花粉形态研究

利用扫描电镜观察了15个中国传统月季品种的花粉形态。结果表明:传统月季花粉为单粒花粉,呈长球形或超长球形（P/E为1.92～2.25）,大小为37.59～51.95 μm×17.02～25.33 μm。赤道面观椭圆形或长矩形,极面观三裂圆形,具三孔沟,沿极轴方向等间距环状分布。外壁纹饰条纹型,覆盖层具穿孔,在品种间具有相似性,但变异丰富,划分为4种类型。聚类分析结果表明,花粉大小和外壁纹饰特征在反映传统月季品种的类别上与形态分类基本一致。根据花粉形态演变规律可推断,样品中‘四面镜’可能为最原始的品种类型,‘月月粉’、‘月月红’及‘匍匐红’等品种较为进化。     

Discrepancies between spontaneous and evoked synaptic potentials at normal, regenerating and botulinum toxin poisoned mammalian neuromuscular junctions

Amplitudes and times to peak of spontaneous miniature endplate potentials (m.e.p.ps) and evoked quantal endplate potentials (e.p.ps) were compared at normal, regenerating and botulinum toxin poisoned neuromuscular junctions of the extensor digitorum longus muscle of the rat. At normal junctions the mean time to peak of m.e.p.ps was longer and more variable than that of similar-sized e.p.ps. At endplates where nerve regeneration was induced by mechanical crushing of the motor nerve the frequency of m.e.p.ps was reduced and their amplitude distribution was broader than normal. The distribution of times to peak of m.e.p.ps was considerably broader than that of quantal e.p.ps recorded at the same endplates. At neuromuscular junctions poisoned with botulinum toxin type A, spontaneous and evoked transmitter release were greatly reduced. The amplitude distribution of m.e.p.ps was wider than that of e.p.ps and the time to peak of e.p.ps was about twice as fast as and less variable than that of m.e.p.ps. To explain the observed differences in time to peak among m.e.p.ps and between m.e.p.ps and quantal e.p.ps we suggest that some m.e.p.ps, but not e.p.ps, originate from transmitter quanta released from sites at a greater distance from postsynaptic receptors or that the release or diffusion process for acetylcholine is more prolonged when producing some of the m.e.p.ps. Such mechanisms produce at normal junctions a small population of m.e.p.ps with prolonged times to peak, at regenerating junctions a greater proportion of such m.e.p.ps and in botulinum toxin poisoning a majority.     

Studies on synaptic transmission in spinal cord cultures: a comparison of postsynaptic actions of classical neurotransmitters with the peptides

The postsynaptic action of the classical neurotransmitter noradrenaline (NA), the reversal potential of the excitatory postsynaptic potential (EPSP) and the effects of divalent cations on EPSPs in dissociated spinal cord cultures are described. In co-cultures of locus coeruleus explant and spinal cord cells, it was found that NA could mimic the response evoked by stimulation of the explant on the spinal cord cells surrounding the explants. Both depolarization and hyperpolarization responses were observed. On a few occasions, a biphasic response consisting of a hyperpolarization followed by a depolarization was observed. The depolarizing response was associated with an increase in input resistance of the membrane. This would suggest that NA may have a facilitatory effect on synaptic transmission. The depolarizations were antagonized by the α-antagonist piperoxane, and were not affected by the β-antagonist propranolol at the concentrations tested, indicating that the receptor mediating these responses is of the α-type. The reversal potential for dorsal root ganglion and spinal cord cells was +8±3.2 mV (mean±s.e.m.), and that for spinal cord and spinal cord cells was ?4±4.3 mV (mean±s.e.m.). These values are different from those previously reported for glutamate in spinal cord cultures. The effects of high and low concentrations of calcium ions on quantal output and mean quantal amplitude or quantal size of the EPSP were further examined. As expected, the cation had an effect mainly on the release process: increasing the concentration of calcium increased the amount of neurotransmitter released, while reducing the concentration of calcium reduced release. Quantal size was slightly or not affected by alteration of external calcium. In comparing the postsynaptic actions of classical neurotransmitters to those of peptides, there is apparently no evidence that the actions of the two groups of agents on central neurons are different. It appears, however, that the peptides generally elicit responses at lower concentrations than the classical neurotransmitters. Further experimentation is required to fully elucidate the actions of peptides on mammalian central neurons.     

Essential oils from buds and leaves of two hazelnut (Corylus L.) cultivars with different resistance to filbert big bud mite (Phytoptus avellanae Nal.) and filbert aphid (Myzocallis coryli Goetze)

The aim of this study was to identify the allelopatic effect of the components of a mixture of essential oils (EO) contained in the buds and leaves of hazel (Corylus L.) on herbivores. We examined the effect of these compounds on the choice of plants of two different hazel cultivars by Phytoptus avellanae Nal. (filbert big bud mite) and Myzocallis coryli Goetze (filbert aphid), which are the most important pests of hazel in Poland and throughout the world. Our results show that plants of cv. ‘Mogulnus’ were more resistant than those of cv. ‘Barra’ to the feeding of mites and aphids in all study years. Using gas chromatography (GC) and GC/mass spectrometry methodology, we determined the qualitative and quantitative composition of EO in the buds and leaves of plants of these two hazel cultivars. The EO obtained from the analysed materials was a mixture of mono- and sesquiterpenes. The emission of volatile organic compounds from plants is known to repel or attract pests. The mixture of EO present in the hazel buds of cv. ‘Mogulus’, which is resistant to filbert big bud mite, was characterized by a high content of nerol, α-campholenol, methyl salicylate, spatulenol, β-caryophylene and δ-cadinene. In contrast, the leaves of this cultivar, colonized by filbert aphid but to a relatively small extent, contained greater quantities of nerol, α-campholenol, p-cymene, α-terpineol and germacrene D, than the leaves of cv. ‘Barra’, which is more accepted by aphids. However, the leaves of cv. ‘Barra’ were characterized by a considerably high content of menthol, limonene, isomenthone, methyl salicylate and L-menthone.     

Fruit misshapen in strawberry cultivars (Fragaria×ananassa) is related to achenes functionality

Fruit deformation is a phenomenon commonly observed in commercial strawberry cultivars (Fragaria×ananassa) with a negative impact on the economic benefit of crop production. To better understand this physiopathy, we evaluated fruit size and the relative amount of ‘small’ (<0.4 mm) and ‘big’ achenes (>0.6 mm) in misshapen (MF) and well‐formed (WF) fruits from ‘Camarosa’, ‘Ventana’ and ‘Medina’ strawberry cultivars growing in the field. In ‘Camarosa’, size‐dependent achenes functionality was assessed by analysing achenes germinability and differences in time to ripening between MF and WF. We found that the occurrence of fruit deformation was not only strongly dependent on the cultivar (i.e. genetic factor) but also was promoted by low temperatures (i.e. environmental factor). Regardless of the cultivar, MF showed higher percentage of ‘small’ non‐functional achenes than WF, indicating a failure in achene development, which could be related to the functional integrity of reproductive structures. To test this hypothesis, we performed an experiment by pollinating strawberry flowers with pollen developed under low and mild temperatures. Low temperatures reduced pollen viability, and flowers pollinated with low quality pollen led to a higher amount of MF. However, fruit deformation was not completely explained by differences in pollen quality, neither by differences in pistil maturity and receptivity nor ovule viability, suggesting that non‐functional achenes might result from a disruption in postfertilisation processes such as embryo abortion as a consequence of low temperatures.     

Continuous infusion of substance P into rat striatum alleviates nociceptive behavior via phosphorylation of extracellular signal‐regulated kinase 1/2

Intraplantar injection of 0.4% formalin into the rat hind paw leads to a biphasic nociceptive response; an ‘acute’ phase (0–15 min) and ‘tonic’ phase (16–120 min), which is accompanied by significant phosphorylation of extracellular signal‐regulated kinase (ERK)1/2 in the contralateral striatum at 120 min post‐formalin injection. To uncover a possible relationship between the slow‐onset substance P (SP) release and increased ERK1/2 phosphorylation in the striatum, continuous infusion of SP into the striatum by reverse microdialysis (0.4 μg/mL in microdialysis fiber, 1 μL/min) was performed to mimic volume neurotransmission of SP. Continuous infusion for 3 h of SP reduced the duration of ‘tonic’ phase nociception, and this SP effect was mediated by neurokinin 1 (NK1) receptors since pre‐treatment with NK1 receptor antagonist CP96345 (10 μM) blocked the effect of SP infusion. However, formalin‐induced ‘tonic’ phase nociception was significantly prolonged following acute injection of the MAP/ERK kinase 1/2 inhibitor PD0325901 (100 pmol) by microinjection. The coinfusion of SP and PD0325901 significantly increased the ‘tonic’ phase of nociception. These data demonstrate that volume transmission of striatal SP triggered by peripheral nociceptive stimulation does not lead to pain facilitation but a significant decrease of tonic nociception by the activation of the SP‐NK1 receptor–ERK1/2 system.

     

Identifying plant functional types using floristic data bases: Ecological correlates of plant range size

Abstract. In an effort to identify ‘plant functional types’, the islands floras of Great Britain and Kríti (Crete, Greece) were examined separately for ecological correlates of plant range size. Plant functional types (PFTs) were defined here as categories into which plants could be grouped on the basis of attributes that predict greater or lesser sensitivity to ecological variability. Plant range size indicates commonness of a species and was assumed to be a proxy for ‘ecological flexibility’, i.e. species of larger range sizes can better withstand environmental change and differences than species of smaller range sizes. Using evolutionary comparative methods that account for the effect of taxonomic relatedness, both floras were investigated for the effects on range size of woodiness vs. non-woodiness, trees vs. shrubs, trees vs. herbs and shrubs vs. herbs. The British flora was examined additionally for the effects of wind- vs. non-wind-pollination, self vs. animal pollination and animal vs. non-animal fruit dispersal on range size. Two analyses showed significant effects on range size: for British species, trees had larger ranges than shrubs, and wind- pollinated species had larger ranges than non-wind-pollinated species. It is suggested that the lack of a similar pattern for shrubs and trees in Kríti is because the lower water availability of Kríti imbues shrubs with an ecophysiological advantage not relevant in plants of Great Britain. That trees have larger range sizes than shrubs in Great Britain is ascribed to the greater importance of competition for light when other factors are not at issue. The greater range of wind-pollinated than non-windpollinated species in Great Britain is postulated to be because both mutualists must be capable of invading new areas. This may be termed a ‘cost of mutualism’. In terms of PFTs, the results indicate that ‘life-form’ is too broad a classification category by which to differentiate relative sensitivity to environmental variability in Great Britain, in that there were significant differences in range size of trees and shrubs, but not between either of the two categories and herbs, or between woody and non-woody plants. Although pollination type may predict relative sensitivity to variation in Great Britain, dispersal type will not. Finally, differences between Great Britain and Kríti in relative range size patterns suggests that plant functional types may be specific to a region or set of conditions.     

Apomorphine induced biting and fighting behaviour in reserpinized rats and an approach to the mechanism of action

Various patterns of aggressive behaviour have been induced by drugs. In the present study, the biting and the fighting responses were induced in rats by apomorphine alone, and reserpine plus apomorphine combination respectively, and these could be blocked completely by a dopamine receptor blocking agent. Dopamine, norepinephrine and clonidine given intraperitoneally or intraventricularly failed to induce these responses. Chemical agents known to increase the concentration of dopamine in the brain, induced the biting, but not the fighting response, whereas these behavioural patterns were more intense due to apomorphine in the rats pretreated with reserpine and dopamine or α-methyltyrosine and reserpine combinations. In amphetamine pretreated rats, apomorphine induced intense biting after 10 min and a few bouts of fighting after 30 min. It is suggested that (i) the receptors on which apomorphine acts may be called ‘Apomorphine Receptor’ rather than ‘Dopamine Receptor’, (ii) dopamine incompletely activates these receptors which are sensitised in the absence of catecholamines and induce a higher degree of stereotyped behaviour i.e. fighting, due to apomorphine.     

Fate of a liposome-associated agent injected into normal and tumour-bearing rodents. Attempts to improve localization in tumour tissues.

Liposomes containing ¹¹¹In-labelled bleomycin were injected intravenously into normal and tumour-bearing rodents and the fate of radioactivity followed. ¹¹¹In levels in tissues retained their maximum values for up to 48h after treatment thereby enabling accurate estimations of tissue participation which with a variety of tumours (Meth ‘A’, 6C3HED, Lewis lung carcinoma and Novikoff hepatoma) in mice and rats was secondary to that of the liver and spleen. Reductions in the size of liposomes decreased liver and spleen participation and increased tumour and kidney involvement. Uptake by lungs, skeletal muscle and brain was also augmented albeit to a lesser extent. Incorporation of anti-Meth ‘A’ cells IgG immunoglobulin into the liposomal carrier led to a modest increase in the uptake of co-entrapped ¹¹¹In by the Meth ‘A’ tumour implanted subcutaneously. Although at the same time, liposomal IgG reduced uptake by the kidney, it effected a drastic increase in hepatic and splenic involvement. This could be prevented by the concurrent administration of excess “empty” liposomes which, however, did not interfere with uptake by tumour tissue.