A phase 1 study of OSI-930 in combination with erlotinib in patients with advanced solid tumours

AIM

To determine the maximum tolerated dose (MTD) of OSI-930 that can be combined with erlotinib, and establish recommended phase 2 doses when both agents are administered daily in patients with advanced solid tumours.

PATIENTS AND METHODS

Eligible patients with advanced solid tumours were enrolled into this standard "three+three" dose escalation study. Study treatment commenced on day 1 with OSI-930, and erlotinib was introduced on day 8. PK profiles of OSI-930, erlotinib and its active metabolite, OSI-420, were determined. Changes in sVEGFR2 as a pharmacodynamic biomarker of OSI-930 activity were assessed.

RESULTS

Twenty one patients were enrolled to 1 of 3 cohorts: 200 mg OSI-930 BID+100 mg erlotinib QD; 200 mg OSI-930 BID+150 mg erlotinib QD; 300 mg OSI-930 BID+150 mg erlotinib QD. The most common adverse events were anorexia (85%), diarrhoea (75%), rash (70%) and lethargy (65%). The MTD was not reached but the onset of cumulative toxicity necessitating dose modification after the 28-d DLT assessment period was common at the highest dose level. A PK interaction was identified with co-administration of both agents resulting in a two-fold increase in OSI-930 exposure. Pharmacodynamic activity was observed with a decline in sVEGFR levels detected in all patients. Ten patients had disease stabilization (median duration 119 d).

CONCLUSIONS

200 mg OSI-930 BID+150 mg erlotinib QD were the recommended doses for further evaluation of this combination.

61. GP PERSPECTIVES ON PARTNER NOTIFICATION FOR CHLAMYDIA

As part of a larger, combined qualitative-quantitative study of partner notification, 40 semi-structured in-depth telephone interviews were conducted with General Practitioners (GPs), from Victoria, ACT and Queensland, who had diagnosed at least one case of chlamydia in the last year. Rural doctors and those who had experience working with Aboriginal patients were over-sampled to ensure their views were represented in the study. The interviews explored GPs' current practices with regard to partner notification for chlamydia, barriers they perceived to partner notification for chlamydia in the general practice setting and what resources/incentives they felt would improve partner notification for chlamydia. The GPs in our study primarily ask the index patient to carry out partner notification themselves. It was relatively rare for GPs to have experience of notifying partners on the patient's behalf. Half of the GPs report that they only encourage notification of the patient's current/immediate past partners. There was considerable confusion amongst the GPs interviewed as to the role of government partner notification officers. Many thought that support from a government agency would allow partner notification to occur more effectively. Some were under the impression that this process is automatically activated when they 'notify' that they have diagnosed someone with chlamydia. Some of the main barriers perceived include confusion about issues of privacy and confidentiality with regard to partner notification and the sense that there is a lack of clarity as to what is expected of them in terms of partner notification for chlamydia. Most GPs feel that access to decision support tools and clear guidelines would be helpful. Financial incentives for doing partner notification were seen as particularly important to fund allied health workers' time rather than to pay GPs themselves e.g. for practice nurses and Aboriginal health workers. GPs were enthusiastic about computer based resources to aid in partner notification

17. PATIENTS' PERSPECTIVES ON THE BEST WAYS TO TELL PARTNERS ABOUT CHLAMYDIA: HOW ACCEPTABLE ARE THE NEW TECHNOLOGIES?

As part of a larger, combined qualitative-quantitative methods study of partner notification, 40 in-depth telephone interviews were conducted with patients diagnosed with Chlamydia from clinics in Victoria, ACT and Queensland to determine their usage and opinions of different methods partner notification. Overwhelmingly, personal methods such as telling partners face-to-face or over the phone were preferred to impersonal methods such as email, SMS and letter. Face-to-face was considered the "gold standard" in partner notification because it demonstrated courage, caring and respect. Phone contact, while considered insensitive and cowardly by some, was often used because it was quick, convenient and less confronting. Email was viewed as only being acceptable in certain circumstances, such as if the partner was overseas, because it was seen as impersonal and uncaring. SMS was considered the least acceptable method for telling partners with most interviewees seeing it as cold, disrespectful and "gutless". However, interviewees who were fearful of their partner's reaction or who had high numbers of casual partners were enthusiastic about an anonymous SMS facility. For both emails and SMS, interviewees were concerned that the message could be misunderstood, not taken seriously or shown to others. Letters, both from the patients or from their doctor, while not viewed as unfavourably as the newer technologies were less likely to be used. These findings suggest that people diagnosed with Chlamydia are reluctant to use the new technologies for partner notification, except in specific circumstances, and our efforts in developing partner notification resources may best be focused on giving patients the skills and confidence for personal interaction.

60. THE RIGHT THING TO DO: PATIENTS' VIEWS AND EXPERIENCES OF TELLING PARTNERS ABOUT CHLAMYDIA

Partner notification for patients diagnosed with chlamydia is recommended to assist in controlling the increasing incidence of this often asymptomatic but treatable infection. Few studies, however, have ascertained the views on partner notification from those who are often expected to perform it - the individuals who have been diagnosed with chlamydia. As part of a larger combined qualitative-quantitative methods study of partner notification, 40 in-depth telephone interviews were conducted with people diagnosed with chlamydia from clinics in Victoria, ACT and Queensland. Reactions to chlamydia diagnosis, as well as reasons for, and feelings about, telling their sexual partners about this infection were explored. Common reactions to initial diagnosis were surprise, shock and shame, as well as relief about being able to put a name to symptoms. Many spoke of relief on learning the condition was treatable. Both men and women commonly saw partner notification as a social duty, and cited concerns about their own health and the health of others as a reason for telling partners and ex-partners about the diagnosis. An infrequent reason offered for partner notification was to confront a partner to clarify fidelity. Reasons for not contacting a partner were typically fear of reaction, or a lack of contact details. Although participants reported sexual partners exhibiting a variety of reactions when told of the diagnosis, results showed that for almost everyone, the experience of notifying their partner was better than they had expected. Views about taking antibiotics to the partner varied according to the currency of the relationship, with some feeling it could be offered as appeasement, and others feeling it might be seen as intrusive. Overall, the findings from this study suggest that partner notification by people diagnosed with chlamydia is achievable, with many of these results likely to be transferable to other settings.

Production of biologically active equine interleukin 12 through expression of p35, p40 and single chain IL-12 in mammalian and baculovirus expression systems

Interleukin-12 (IL-12) is a key cytokine in the development of cell-mediated immune responses. Bioactive IL-12 is a heterodimeric cytokine composed of disulphide linked p35 and p40 subunits. The aim of this study was to verify biologically activity of the products expressed from equine interleukin-12 (IL-12) p35 and p40 cDNAs and to establish whether equine IL-12 could be expressed as a p35/p40 fusion polypeptide, as has been reported for IL-12a of several mammalian species. We report production of equine IL-12 through expression of p35 and p40 subunits in mammalian and insect cells and of a p35:p40 fusion polypeptide in mammalian cells. Conditioned medium recovered from cultures transiently transfected with constructs encoding equine p35 and p40 subunits or single chain IL-12 enhanced IFN-gamma production in cells derived from equine lymph nodes. Preincubation of IFN-gamma inducing preparations with anti-p40 monoclonal antibody resulted in a significant decrease in IFN-gamma induction capacity. Medium recovered from p35 and p40-expressing baculovirus infected cultures enhanced target cell IFN-gamma production and proliferation. Experimental studies in mice and other animals have revealed a therapeutic benefit of IL-12 in cancer, inflammatory and infectious disease and an adjuvant effect in prophylactic regimes. Production of a bioactive species-specific IL-12 is a first step towards an investigation of its potential application in equine species.

Inhibition of growth of a tapeworm Hymenolepis diminuta in its normal host (rat)

The biomass of 8-day-old worms of Hymenolepis diminuta in secondary infections, administered to rats 3-10 days after chemotherapeutically expelling a primary infection, was 70-90% less, and the worms were more posteriorly distributed, than in naive controls. The strong depressive effect on growth waned rapidly over 2-5 weeks, but even in rats not challenged until 17 months later, worm growth was weakly depressed by 30%. The extent to which growth was depressed in a secondary infection was independent of the number of worms in the challenge but increased with number of worms in the immunizing infection up to four to eight worms. Further increase up to 64 worms had little effect. This suggests, as it is known that the biomass of worms in a rat reaches a maximum with infections of between five and 10 worms, that the change in the intestine is proportional to biomass, not number, of worms. It is argued that partially suppressed immuno-inflammatory changes in the intestine, which will affect secondary worms so strongly, will also have depressed growth and fecundity effects on the primary worms, that a dynamic equilibrium is reached between the strength of the intestinal response and the biomass of the tapeworm, and that it is reaching this equilibrium, not a 'crowding effect', which limits H. diminuta to a level compatible with the survival of the rat.

Production of toxic shock syndrome toxin 1 in a mouse model of Staphylococcus aureus abscess formation

A mouse model of abscess formation is described in which toxic shock syndrome toxin 1 (TSST-1) is produced by Staphylococcus aureus in vivo. Mice injected intravenously with S. aureus developed renal abscesses within 4-7 days. Kidneys excised from infected mice were cultured quantitatively, and extracts from the kidneys were assayed for TSST-1 with use of a competitive enzyme-linked immunosorbent assay. Animals with less than 10(7) S. aureus/g of kidney had less than 6 ng of TSST-1/mL of extract. Toxin levels ranged from less than 6 ng/mL to 271 ng/mL in kidney extracts from mice with greater than 10(7) S. aureus/g of kidney. Urine from infected mice also contained measurable levels of TSST-1 (range, less than 6-728 ng/mL). Mice developed serum antibodies to TSST-1 by 2 weeks after challenge. Serum samples collected 5-7 days after bacterial challenge did not show biochemical changes typical of a toxic shock-like illness in these animals.

Purified capsular polysaccharide-induced immunity to Staphylococcus aureus infection

In this study, we determined that immunization with capsular polysaccharide from Staphylococcus aureus could protect mice against nonlethal infections induced by encapsulated staphylococci. We immunized mice with either formalin-killed bacteria or purified capsular polysaccharide (PCP) and challenged them with one of three related S. aureus strains that varied in capsule size. Quantitative cultures of blood and kidney from the animals were performed to evaluate protection. Immunization with whole bacteria protected mice against infection with the homologous strain. Mice immunized with PCP were protected when challenged intravenously with either a highly encapsulated S. aureus strain or a microencapsulated mutant but not with an unencapsulated mutant. Protection correlated with capsular antibody levels in the immunized animals. Immunity to staphylococcal infection could be passively transferred to naive animals by using immune serum. These experiments suggest that the S. aureus capsular polysaccharide merits further study as a potential vaccine candidate for preventing staphylococcal infection.

Virulence studies, in mice, of transposon-induced mutants of Staphylococcus aureus differing in capsule size

We used three related strains of Staphylococcus aureus to determine whether capsule size influenced bacterial virulence. Strain SA1 mucoid elaborated a large capsule demonstrable by transmission electron microscopy (TEM). Nonmucoid isolates were derived from strain SA1 mucoid by Tn551 insertional mutagenesis. By TEM, strain JL24 produced a "microcapsule," whereas strain JL25 was unencapsulated. Strain SA1 mucoid had a 50% lethal dose for mice greater than 3,000-fold lower than that of strains JL24 and JL25. Quantitative cultures of blood and kidney from animals challenged intravenously revealed that strain SA1 mucoid was cleared less readily from the bloodstream and kidneys than the nonmucoid mutants. In an in vitro assay, only strain SA1 mucoid demonstrated antibody-dependent, complement-mediated opsonophagocytosis by human leukocytes. Strains JL24 and JL25 were opsonized for phagocytosis by complement alone. Thus a highly encapsulated strain of S. aureus was more virulent in mice than two related nonmucoid strains. The microencapsulated mutant was not more virulent than the unencapsulated mutant.

Chemical characterization and immunogenicity of capsular polysaccharide isolated from mucoid Staphylococcus aureus

In this study we report the isolation and purification of the capsular polysaccharide elaborated by Staphylococcus aureus SA1 mucoid. The capsule was isolated from bacterial extracts and culture supernatants by a series of ethanol precipitations and enzyme digestions, followed by ion-exchange chromatography. Teichoic acid contamination was eliminated by oxidation with sodium metaperiodate, and the final product eluted in the void volume of a Sephacryl S-300 column. The purified capsular polysaccharide was analyzed by gas-liquid chromatography-mass spectroscopy, 13C and 1H nuclear magnetic resonance, amino acid analysis, immunelectrophoresis, and numerous biochemical assays. The major constituents of the capsule were 2-acetamido-2-deoxy-alpha-galacturonic acid (4-O linked), 2-acetamido-2-deoxy-alpha-fucose (3-O linked), and taurine. The polysaccharide also contained O-acetyl groups which were removed by mild alkaline hydrolysis. Serologically and biochemically, the capsule from strain SA1 mucoid appeared very similar to that produced by strain M. Purified capsular polysaccharide was immunogenic in both rabbits and mice. The optimal immunizing dose in mice was 0.1 microgram of purified capsular polysaccharide administered intraperitoneally. SA1 mucoid resisted opsonophagocytic killing by human leukocytes and complement. However, antibodies raised to the purified capsular polysaccharide neutralized the antiphagocytic effect of the capsule.

Hymenolepis diminuta: ultrastructural abnormalities in worms from C57 mice

Ultrastructural studies, including stereological analyses of micrographs, have been made of five-worm primary infections of Hymenolepis diminuta from C57 mice to determine whether the immune destrobilation/rejection process was accompanied by significant changes in the fine structure of the scolex tegument. Destrobilation/rejection of worms occurred from Days 9-12 after infection. For the first 5 days after infection, the scolex tegument showed no detectable differences in ultrastructure compared with that of "control" worms from either Wistar rats or immunosuppressed C57 mice. By Day 6, large lipid deposits were observed in the tegument and associated musculature of worms from untreated C57 mice. Further, worms recovered from Days 6-8 after infection also showed increased activity of the Golgi apparatus, GER, and mitochondria of the tegument, resulting in increased numbers of discoidal secretory bodies. Concomitant with destrobilation/rejection from Day 9 was a drop in the number of secretory bodies, an increase in autophagic activity throughout the tegument, and a blistering of the tegument surface plasma membrane. The possible functional significance of the results is discussed in relation to host immunity.

Pulmonary infection with opportunist mycobacteria on Merseyside 1974-1983

During a 10 year period 49 patients were recorded as having pulmonary infection caused by opportunist mycobacteria. Six different species were identified of which M. kansasii (65%) and M. avium-intracellulare (20%) were the most common. Cough and sputum (82%) or haemoptysis (26%) were frequent symptoms on presentation and over two thirds of patients had pre-existing respiratory disease. Chest radiographs showed predominantly apical disease with the right apex (44%) being twice as commonly affected as the left (22%). In 30% the radiograph showed bilateral disease. Clinicians had an individual approach to treatment with no uniform pattern of drug prescribing. A majority of patients (59%) received rifampicin for at least 9 months and those patients with M. kansasii infection responded well with no bacteriological relapses in 20 patients followed for a mean period of 3.9 years. M. avium-intracellulare, M. malmoense and M. xenopi were less responsive to treatment and in four patients receiving chemotherapy death was attributed to mycobacterial infection.

Immunological memory in mice to adult Hymenolepis diminuta (Cestoda)

Following a primary infection with Hymenolepsis diminuta mice were found to be strongly resistant to a challenge infection over a period of eight months. Challenge was by three cysticercoids administered orally, or by inserting into the duodenum one 7-day-old strobilate worm recovered from a donor mouse. Autopsy of immunized mice 6, 8, and 9 days after challenge showed that challenge worms established but that, with few exceptions, only shunted or destrobilated worms remained. Autopsy of recently immunized mice, at daily intervals following challenge, confirmed that transplanted worms establish as well in immunized as in naive mice, and showed that worms grow normally for the first 48 hr but between 48 to 120 hr most worms destrobilate or are lost. In naive mice, transplanted worms survive and grow, approximately doubling their weight daily for at least 6 days (144 hr). The results provide insight to the problem of developing a useful vaccine and the location of memory cells.

Raillietina cesticillus: rejection by bursa-deficient chickens

Chickens in which antibody-forming capacity was abrogated by bursectomy and irradiation developed protective immunity against Raillietina cesticillus as effective as controls which had specific antiworm antibodies in their sera and immunoglobulin positive cells in splenic and intestinal tissues. It is concluded that antibodies are not essential for the rejection of the tapeworm by chickens and may even retard rejection.

Immunologically mediated rejection of Hymenolepis diminuta by its normal host, the rat

The adult tapeworm, Hymenolepis diminuta, living in the lumen of the intestine of its normal rat host was shown to sensitize the intestine. The growth of worms in a secondary infection, given 8, 23, or 41 days after the primary infection had been removed by anthelmintic treatment, was 0.5, 3, and 25%, respectively, of that in the control worms. Thus, there is a strong initial resistance to a challenge infection, but this resistance weakens fifty-fold between days 8 and 41 postinfection. Even primary infections of five worms, which would have survived indefinitely if not expelled by anthelmintics, depressed the growth by over 80% of secondary infections given 8 days later. Rats given a light primary infection manifested their sensitivity only by depressing the growth of challenge worms, but in strongly sensitized rats, worm growth was stunted severely (or the worms destrobilated), partial worm expulsion occurred, and the remaining worms migrated to a more anterior position in the intestine. We suggest that the rapid waning of memory indicates that the protective mechanism evoked in the intestine has as its primary biological function the limitation of the number of worms that can accumulate in the intestine in concurrent infections, not the prevention of reinfection after the loss of worms from previous infections.

Hymenolepis diminuta: the role of the tail in determining the position of the worm in the intestine of the rat

One-worm infections of Hymenolepis diminuta in rats had their strobila severed surgically, in the neck region, on day 14 of an infection. The scolex and remaining strobila survived but were recovered from a more posterior region of the intestine where small worms are attached during development. The movement to the new region was usually not complete in 24 h, but was complete by 72 h, and probably by 48 h. The operation, involving laparotomy and an incision in the duodenal wall which avoided severing the strobila, had no effect on the position of the worm but did depress the growth of the worm during the ensuing 24 h. It is suggested that (1) the preferred site for H. diminuta is 30-50% down the small intestine, (2) the worm monitors information about its position from all over its strobila and (3) as the worm grows, its position is determined by balancing the input of adverse information from its tail and head ends. The slowness with which surgically shortened worms return to the preferred site may be due either to delay in the worm "realising" it has no tail, or to the location stimuli in the intestine being disturbed for 24 h by the operation.

Comparison of polymer, glucose, and hydrostatic pressure induced ultrafiltration in a hollow fiber dialyzer: effects on convective solute transport

Ultrafiltration induced by (1) poly(sodium acrylate), (2) glucose, and (3) hydrostatic pressure was studied in a hollow fiber dialyzer. Poly(sodium acrylate) added to dialysate induced large amounts of ultrafiltration without crossing the dialyzer membrane. Sodium ions of the acrylate polymer were osmotically active but were held in dialysate by the impermeant anionic polymer. The hydrostatic pressure equivalent of osmotic pressure induced primarily by the sodium ions approximated that predicted for a completely impermeant molecule. The apparent (net) sieving coefficients for vitamin B12 observed during polymer and hydrostatic ultrafiltration studies were both significantly higher than that observed during glucose ultrafiltration but did not differ from each other. These studies suggest that sodium salts of polyanions can provide an osmotic driving force to yield large amounts of ultrafiltration in dialysis systems and yet not cross the membrane. The studies also suggest that relatively less efficient convective transport with glucose as compared to hydrostatic pressure is neither a membrane phenomenon nor a characteristic of all osmotic pressure induced ultrafiltration. Relatively low effective solute sieving appears to be associated with osmotic induced ultrafiltration with a permeant solute. Under such conditions it is proposed that molecular interaction within the membrane impairs convective transport.

Effects of ultrafiltration on solute clearances in cuprophan and cellulose hollow fiber dialyzers: in vitro and clinical studies

Hollow fiber dialyzers are currently available with either regenerated cellulose or thinner walled cuprophan fibers. In vitro and clinical studies were undertaken to compare a cellulose with a cuprophan dialyzer in regard to (1) UF's, (2) small and large solute clearances at high and low TMP's, (3) SC's, and (4) effects of ultrafiltration on diffusive and convective components of clearances. The results show that per square meter of surface area, the cuprophan dialyzer has higher rates of UF per TMP and greater clearances, particularly of larger solutes; also with cuprophan the SC for vitamin B12 is higher. Thus all findings suggest greater permeability of cuprophan fibers. In both dialyzers, total clearances increased with UF by amounts compatible with predicted increases in convective transport; diffusive transport remained stable as TMP was increased.

Effects of ultrafiltration of diffusion and convection in two newer coils

Clearances of sodium and B12 were measured with increasing ultrafiltration in two newer coils with new types of membrane support. In all other coil studies previously reported, clearance increases with ultrafiltration did not equal predictions from contributions of convection implying simultaneous decreases in diffusive solute transport with increasing transmembrane pressure. Such deterioration was attributed to masking of membrane surface area by the membrane support, widening of blood channels, and/or channeling of dialysate flow. In these newer coils, clearance increases were very near to predicted enhancement by convection while diffusion was stable in one type and decreased only modestly in the other. Coil volumes assessed with the kerosene technique increased with higher transmembrane pressure similar to findings in previous coils studies. Thus, although coil blood path dimensions are altered with increasing pressure as in older coils, diffusive clearances remain stable and increases in total clearances equal that predicted from convective solute transport. These results suggest that membrane masking is probably the major mechanism for decreases in diffusion with ultrafiltration in other coils and that the problem has been minimized with improved membrane supports.

Transplantation of Hymenolepis diminuta into naive, immune and irradiated mice

Almost 100% of 7- to 10-day-old Hymenolepis diminuta became established when surgically transplanted from donor mice into the duodenum of naive recipient mice. Transplanted tapeworms survived 8-12 days, by which time they had survived much longer in total than they would have done in the donor. Mice previously immunized by a primary infection rejected transplants within 4 days. Sub-lethal irradiation (550 rad) delayed rejection by immune mice but such mice still rejected worms much more quickly than did naive mice. Surgery was shown to delay by 2-3 days the rejection of worms by naive mice, and the importance of circumventing surgery by administering the worms per os is emphasized. Prospects for reconstituting irradiated immune mice are considered vis-à-vis work with nematodes, and the differences which, on present knowledge, appear to exist between nematode and cestode rejection are briefly discussed.

Immunity to intestinal tapeworms: the rejection of Hymenolepis citelli by mice

Approximately 90% of Hymenolepis citelli cysticercoids given to 6-week-old male CFLP mice by stomach tube became established. Equally high recovery rates were obtained from administering 1, 3 and 6 cysticercoids.

In 1-worm infections worms increase in weight until about day 25–28 post infection. After a few days at maximum weight (mean weights of worms 24–42 mg) there is a small, 10–25%, decrease in weight, after which there is little change in weight up to day 90 (as long as studied).

One-worm infections survived without loss until day 30, after which a slow loss occurred, but only in two experiments, both with older mice, did loss exceed 50% by day 80. In 3-worm infections worms were rejected between days 17 and 30, but loss varied from 50 to 80% during this period in replicate experiments. With 6-worm infections rejection occurred over a shorter period (days 17–22), was more uniform between experiments and was more complete, over 75% of worms being lost. In both 3- and 6-worm infections a residual population, usually of only a single worm, persisted in 20–50% of the mice until the end of the experiments (day 63–78).

Cortisone prevented loss of worms from both 3- and 6-worm infections; worms continued to grow until day 25 ± 2 (as in 1-worm infections), by which time they were considerably larger than (the surviving) worms in mice not receiving cortisone. The biomass (worm burden per mouse) remained constant from day 25 to 55 in mice receiving cortisone.

The results are discussed with particular reference to: H. diminuta and the evidence that mice do mount an immunological response against tapeworms in the intestine; the existence of an antigenic threshold in mice; the apparent existence of a similar rejection pattern in a natural population of H. citelli in Peromyscus maniculatus, and hence the importance of immunity as a factor preventing gradual increase in number of tapeworms in the intestine during the life of a host.

The effect of oxyclozanide on Hymenolepis microstoma and H. diminuta

The effect of oxyclozanide (2,2′-dihydroxy-3,3′,5,5′,6-pentachlorobenzanilide) on Hymenolepis microstoma in the bile duct of mice, and H. diminuta in the small intestine of mice and rats was measured. Oxyclozanide at doses as low as 4mg/kg removed 13-day-old H. diminuta and caused no obvious harmful effect to the rat host up to the maximum level (256 mg/kg) tested. Worms were displaced and degenerating within 1 h. Results in mice were more difficult to assess because of the immune response, but similar total amounts of oxyclozanide caused destrobilation and loss of 7-day-old H. diminuta. Oxyclozanide was less effective against 21-day-old H. microstoma attached in the bile duct. Approximately half the strobila was lost following dosing at 5 mg/kg and progressively greater amounts as the dose level was increased. At 50 mg/kg worm loss commenced but even at 150 mg/kg 25 % of worms survived. The time taken to regrow to the original adult size varied but was complete within 7–9 days at levels up to 25 mg/kg. Double dosing at 5-day intervals did not enhance the effect of a single dose. The apparent existence of a sensitivity gradient down the strobila in H. microstoma is discussed.

The effect of immunosuppressants on the development of Hymenolepis diminuta in mice

Cortisone, methotrexate and anti-lymphocyte serum were all found to suppress the rejection by SPF CFLP male mice of H. diminuta, which normally occurs between days 9 and 12. Worms continued to grow in mice given immunosuppressants and matured on days 16–18 as they would in a rat, by which time they stretched from the stomach to, and sometimes into, the caecum. Worms in mice given methotrexate ceased to grow after day 16, but this was believed to be due to the deterioration of the host's intestine wall; in mice receiving cortisone growth was faster than normal and worms continued to increase in size until the end of the experiments on days 20–24. The mouse/H. diminuta system is discussed, emphasizing that, as far as is known, H. diminuta (which has no hooks) has no close contact with the tissues and that this is a case of a mammal responding against an organism living freely in the lumen.

The development of Hymenolepis diminuta in primary and secondary infections in mice

Over 90% ofHymenolepis diminutacysts administered by stomach tube become established in CFLP, and Porton strains of mice. The rate of growth of single worm infections in terms of dry weight and length was determined. The rate of growth ofH. diminutain mice is slower than in rats even in worms only a few mm long. In most mice growth ceases abruptly on day 10±1 day when the worm is 4–30 cm long, destrobilation usually occurs leaving a scolex and neck often 0·5–2 mm in length. Destrobilated worms can survive for at least 47 days but little if any regrowth occurs unless the worms are surgically transplanted into rats or previously uninfected mice. Normal growth appears to be resumed within hours in both recipient hosts. The cause of destrobilation is probably not physiological; position of establishment and forward migration during growth of the worm in mice is similar to that in a rat. Destrobilation occurs well before the worm fills the small intestine lengthwise. Strong evidence of an immunological response being involved is given by the fate of a secondary infection given 22 and 28 days after the primary. Lower % recoveries were recorded in secondary infections killed 6–9 days later, and the worms were severely stunted. The various lines of evidence are discussed and it is concluded no reasonable doubt exists thatH. diminutais rejected by CFLP and Porton mice as a result of an immunological response.

Diurnal movement of Hymenolepis diminuta in the rat

Following a 2–5 ml meal containing 2 g (80%) glucose and 30 mg methionine administered by stomach tube at 09.00 h,H. diminutawas found to change its position in the rat's intestine. Usually while the stomach contained food ≤ 45 %, by weight, of the tapeworm lay in the posterior 40 % of the small intestine, after the stomach was empty the reverse was true.

The effect of hyperosmotic fluid entering the duodenum was determined by injecting, following laparotomy, varying amounts of 80 % glucose and 1 ml of varying concentrations. A volume ≤ 0-4 ml of 80 % led to the death and expulsion of worms within 7 h, and 1 ml of < 50 % glucose also killed the worms.

The expulsion of 15 % of the tapeworms from rats given 2–5 ml hypertonic meal by mouth was correlated with the failure of the stomach in some rats to regulate the stomach emptying. Worms in these rats were found from 4 h onwards in the caecum and large intestine, and by 9 h in the faeces.

That the movement of worms, other than those expelled, was not caused by a sub-lethal flux of hyperosmotic fluid was shown by feeding an iso-osmotic meal to rats; the worms moved to a more posterior position during the day, but none was expelled.

Single worm infections in rats kept on a normal feeding regime until 07.00 h and then starved throughout the day also showed a posterior migration. Using a method which involved the simultaneous cutting of the small intestine into 5 cm sections, it was possible to show that this movement involved the whole worm, the scolex moving from a mean position 10–15 cm to one 20–25 cm from the stomach, and the terminal proglottid moving from approximately 75 cm to 95 cm from the stomach.

Worms in Wistar rats responded similarly to those in SPF CFE (Sprague Dawleys) with the exception that there was some evidence that the stomach emptying of a hyperosmotic meal was better controlled and hence a smaller percentage of the worms were expelled.

The results are discussed in relation to diurnal changes in the level of the external site location stimulus which other workers have shown to exist by surgically transplantingH. diminutainto the ileum.

The enthusiastic assistance of Miss Helen Stallard, B.Sc., and Miss Patricia Grant is gratefully acknowledged, and financial support from the Medical Research Council, London (Grant No. G967/164/T).

The influence of dietary methionine on the amino acid pool of Hymenolepis diminuta in the rat's intestine

The amount of [14C]methionine in the stomach, anterior and posterior intestine wall and lumen, blood and caecum of a rat, and in the anterior and posterior parts of the tapewormHymenolepis diminutain the intestine, was measured at intervals from 10 min to 10 h after feeding a meal of 2 g glucose and 37.5 mg methionine by stomach tube.

Nearly all the meal left the stomach within 5 h; the amount entering the tapeworm depended on the position of the worm. That part lying in the anterior half of the intestine was subjected to a rapid influx reaching a maximum concentration of at least 8 mM within 1–3 h after the meal was administered. The level in the worm then dropped to about 20 % of the peak level, although the stomach was still emptying and the level of methionine in the intestine wall was still rising. This was a stable state, and equal to the concentration in the posterior part of the worm which was reached 2 h after the rat was fed.

The reason why the anterior part of the worm should show a big influx and efflux is discussed and related to changes in concentration of methionine in the lumen. The lack of such a flux into and out of the worm further down the intestine is related to the host's homeostatic control of amino acid balance in the intestine.

The results prove that dietary imbalance of amino acids affect the amino acid pool in a tapeworm for about 3 h, if it lies in the anterior of the gut. A dietary regime is suggested which should produce a prolonged effect and thereby retard growth of the worm.

The weights of the parts of the worms found in the anterior and posterior half of the small intestine revealed an unexpected phenomenon; the majority of the tapeworm, by weight, lies in the anterior of the intestine for about 4 h following a meal, but in the posterior of the intestine after the stomach has emptied.

It is a great pleasure to thank Miss Gillian Moore and Miss Patricia Grant for technical assistance, and Shell International Petroleum Company, London, for financial support.

Maintenance of Schistocephalus solidus in the Laboratory with Observations on Rate of Growth of, and Proglottid Formation in, the Plerocercoid

Procedures for the maintenance of Schistocephalus solidus in the laboratory are described: recovery of eggs from low bulk faeces; incubation and hatching of eggs at 25 C; and infection of Cyclops agilis, Diaptomus gracilis, and Mesocyclops leuckarti with procercoids that at 25 C become infective in 10, 8, and 8 days, respectively. Methods for infecting Gasterosteus aculeatus with specific numbers of plerocercoids, and procedures for maintaining infected sticklebacks, are described. The rate of growth of S. solidus in G. aculeatus at 19 C has been determined up to day 83, by which time plerocercoids are infective and weigh 50 mg fresh weight. The problem of speciation in Schistocephalus is discussed with reference to the conflicting evidence concerning the number of proglottids in the plerocercoid. Statistical evidence shows the number of proglottids increases slowly during growth contrary to previous statements, and ontogenesis is discussed with reference to metamerism. Problems of growth of Schistocephalus in the fish host are enumerated.

The effect of dietary amino acids on the growth of Hymenolepis diminuta

The effect of an amino acid imbalance in the diet on the growth ofHymenolepis diminutain rats was reinvestigated. The claims of earlier workers that growth of the tapeworm is retarded was not substantiated.

The size frequency distribution of 575, 13-day-oldH. diminutarecovered from 9- and 10-worm infections was determined, to reveal the shape of the distribution and total variance. The total variance in worm weights was analysed to determine the amount attributable to variance ‘between rats’ (comparison of the mean weight of the worms recovered from rats) and variance between worms within individual rats. ‘Between rats’ variance was found to account for > 80% of the total variance.

Assuming variance equal to that in the experiments described, the degree to which experiments can determine a difference in effect between two diets on the growth of tapeworms is analysed, and the degree to which this is altered by increasing the number of rats in dietary groups and/or decreasing the ‘between rats’ variance is estimated.

The suitability of various procedures for host dietary experiments on tapeworms is discussed; these include the duration of the experiment, feeding regime, age of worm and the relative advantages of weighing worms singly or in groups.

We gratefully acknowledge the technical help we have received from Miss Patricia Grant and Mr Jack Keys. Our thanks are also due to Mr Robert Elton of the University of Glasgow Statistics Department who has advised us on statistical procedures and calculated Table 6.