Pneumococcal conjugate vaccines.

We have prepared conjugates of pneumococcal type 4 polysaccharides (PS4) or oligosaccharides to tetanus toxoid using the carbodiimide method. The use of a spacer, 6-aminohexanoic acid, resulted in higher incorporation of carrier protein. Conjugates contained up to 10% free polysaccharide, but no free protein. In general, polysaccharide conjugates induced higher anti-PS4 IgG antibody titers than oligosaccharide conjugates. Conjugates with the highest amount of incorporated protein were the most immunogenic. The response to conjugated PS4 does show characteristics of a T cell-dependent antibody response, in terms of both isotype distribution and induction of immunological memory. Repeated immunization with high doses of PS4TT conjugate resulted in a virtually negative anti-PS4 IgG response, suggestive of the induction of high dose tolerance.     

High genetic diversity of HIV-1 strains in Chad,West Central Africa

The genetic diversity of HIV-1 strains in Chad was documented with a total of 107 samples from patients attending the general hospital in N'Djamena, the capital city of Chad. The genetic subtypes were identified in the V3-V5 env and p24 gag regions by sequence and phylogenetic tree analyses. Of the 107 strains, 78 had the same subtype/CRF designation between env and gag. Four subtypes and three CRFs were found to cocirculate: subtype A, 20.5%; subtype D, 18.7%; CRF02_AG, 13.1%; CRF11_cpx, 13.1%; subtype G, 3.7%; CRF01_AE, 2.8%; and subtype F1, 0.9%. The remaining 29 strains (27%) had discordant subtypes or CRF designations between env and gag; in 15 of these 29 strains, a CRF was involved in the recombination event, and 10 were subtype G in gag and subtype A in env, forming a separate subcluster within subtypes G and A. Subtype D strains represent almost 20% of the HIV-1 strains circulating in Chad and form a separate subcluster in gag and env. Nearly full-length genome sequencing for two such strains (99TCD-MN011 and 99TCD-MN012) revealed that they represent nonrecombinant subtype D variants. Compared with neighboring countries, the genetic subtype distribution of HIV-1 strains in Chad is unique for several reasons: lower prevalence of CRF02, high prevalence of CRF11 and subtype D, and absence of CRF06. These data clearly show that subtype distribution is very heterogeneous in Africa, probably the result of different founder effects.     

Oral contraceptive use in relation to age at menopause in the DOM cohort

BACKGROUND: We investigated the hypothesis that long-term use of oral contraceptives (OCs), in particular high-dose OCs, could postpone age at menopause. METHODS: Data was used from 8701 women who participated in a breast cancer screening programme in Utrecht (DOM-3 cohort), and who did not use hormone replacement therapy (HRT) or OCs in the 4 years prior to their last menses. Data on OC-use, menopausal status, age at menopause, year of birth, parity, smoking behaviour, socio-economic status, body mass index and age at menarche was available. Use of high-dose OCs has been defined in this study as OC-use before 1972. The data was analysed by means of linear regression and Cox's proportional hazards analysis. Women still menstruating, women with surgical menopause and women lost to follow-up were censored at their last known date of menstruation. Endpoint was the natural menopause (n = 4589). RESULTS: The use of high-dose OCs advanced the onset of menopause by approximately 1.2 months for every year of OC-use compared with no OC-use. High-dose OC-use for > or = 3 years, adjusted for confounding variables, increased the risk of earlier menopause compared with no OC-use (adjusted hazard ratio 1.12; 95% CI 1.03--1.21). The use of lower dose OCs did not increase the risk of earlier menopause (adjusted hazard ratio 1.00; 95% CI 0.91--1.09). CONCLUSIONS: These results are inconsistent with the hypothesis that long-term use of OCs could postpone the onset of menopause by inhibiting follicle depletion. Possible explanations are discussed.     

Absolute and relative dose-surface and dose-volume histograms of the bladder: which one is the most representative for the actual treatment?

The purpose of this study was to quantify to what extent relative and absolute bladder dose-volume and dose-surface histograms of the planning CT scan were representative for the actual treatment. We used data of 17 patients, who each received 11 repeat CT scans and a planning CT scan. The repeat CT scans were matched on the planning CT scan by the bony anatomy. Clinical treatment plans were used to evaluate the impact of bladder filling changes on the four histogram types. The impact was quantified by calculating for this patient group the correlation coefficient between the planning histogram and the treatment histogram. We found that the absolute dose-surface histogram was the most representative one for the actual treatment.     

Efficient rescue of infectious bursal disease virus from cloned cDNA: evidence for involvement of the 3'-terminal sequence in genome replication

To study the mechanism of replication of infectious bursal disease virus (IBDV), and to determine factors on the IBDV RNA which are involved in viral replication, we used cloned full-length cDNA of both the A- and B-segments to generate infectious IBDV. Infectious IBDV was rescued from plasmids that contained full-length IBDV cDNA behind a T7 promoter, by transfecting these plasmids into cells which were infected with a recombinant Fowlpox virus that expressed T7 RNA polymerase. By using the cDNA transfection system we evaluated the effect of the length of the 3' terminus of the A-segment plus strand of IBDV. Although wild-type IBDV predominantly contains four cytosines at the 3' terminus, no difference in virus yield was found when virus was rescued from cDNAs containing three to six adjacent cytosines. When the 3' terminus was shorter than three cytosines the efficiency to generate infectious IBDV from cDNA was reduced, but IBDV could still be recovered reproducibly. The rescued viruses from cDNAs containing 3'-terminal deletions appeared to have a restored 3'-terminal sequence. The missing nucleotides are probably restored by using complementary bases of a stem-loop structure as template.     

Antecedents and consequences of work-home interference among medical residents

A cross-sectional field study is reported in which a comprehensive model of work-home interference (WHI) was developed and tested among 166 medical residents of an academic hospital in the Netherlands. It was hypothesized that WHI functions as a critical mediating pathway in the relationship between work and home characteristics on the one hand, and work-related and general psychological health indicators on the other. The results revealed that one home characteristic and three work characteristics put pressure on the interface between the work and home life, that is, (1) having a spouse who works overtime frequently, (2) an unfavorable worktime schedule, (3) a high quantitative workload and (4) a problematic dependency on the superior. The results further showed that WHI was positively associated with emotional exhaustion and depersonalization (i.e. work-related health indicators), as well as with psychosomatic health complaints and sleep deprivation (i.e. general health indicators). More importantly, the results strongly supported our basic hypothesis that WHI mediates the impact of some work and home characteristics on psychological health indicators. This seems to be particularly true for the general health indicators: none of the home and work characteristics just mentioned, had a direct impact on these general indicators, independent of WHI. With respect to the work-related health indicators, particularly depersonalization, the mediating role of WHI was also strong, though less consistent. The theoretical and practical implications of the findings are discussed.     

A comparison of the pharmacokinetics and tolerability of riluzole after repeat dose administration in healthy elderly and young volunteers

The pharmacokinetics and tolerability of the novel antiexcitatory agent, riluzole, were compared in 18 healthy elderly and 18 healthy gender- and weight-matched young volunteers. All participants received riluzole 50 mg twice daily (the recommended dosage for patients with amyotrophic lateral sclerosis), administered orally for 5 days. The pharmacokinetics of riluzole, determined on the morning of the 5th day of dosing, were not significantly affected by age or gender. The mean terminal elimination half-life (t1/2), however, was statistically significant between elderly and young subjects. Riluzole was well tolerated upon repeat dose administration. Headache was the most frequent adverse event reported, and there was no overt difference in the type, frequency, or severity of adverse events between elderly and young volunteers or between genders. In conclusion, these results indicate that no dosage adjustments of riluzole are required in the elderly.     

Ca2+ dependence of motilide-induced contractions in rabbit duodenal muscle strips in vitro

Summary Recent studies suggested that certain erythromycin A (EM-A) derivatives are motilin receptor agonists. As proposed by Itoh they may be called motilides. We have investigated the Ca²⁺-dependence of contractions induced by two potent motilides, ME-34 [de(N-methyl) 8,9-anhydroeryhtromycin A 6,9-hemiacetal] and EM-523 [de(N-methyl)-N-ethyl-8,9-anhydro-erythromycin A 6,9-hemiacetal], in duodenal tissues and compared the results with those previously obtained with motilin.Isometric and isotonic contractile responses of isolated longitudinal muscle sheets from the rabbit duodenum were tested under normal, Ca²⁺-free and depolarizing conditions. Prior to stimulation with motilides, the maximal response to acetylcholine was recorded and all responses were always expressed as a percentage of this response. Both motilides induced contractions in normally polarized tissue, with an EC₅₀ of 26 ± 5 nM for ME-34 (n = 7), and 27 ± 5 nM for EM-5231 (n = 16) and maximal responses of respectively 88 ± 4% and 80 ± 3%. Like motilin, both compounds induced an extra-contraction in depolarized tissues. The EM-523 response in 140 mM K⁺under isotonic conditions was 84 ± 3% (n = 5) at 10^–5 M, with an EC₅₀ that was shifted to 65 ± 18 nM. Similar figures were obtained for ME-34. When Ca²⁺ was added to Ca²⁺-depleted strips, half-maximal Ca²⁺ values (in mM) were 1.10 ± 0.11 (n = 9) for EM-523 and 1.13 ± 0.12 (n = 3) for ME-34, as compared with 1.12 ± 0.13 (n = 7) for motilin and 2.8 ± 1.1 (n = 9) for K⁺. Both ME-34 and EM-523 also induced a transient contraction in Ca⁺-free solutions under isometric conditions. The response to EM-523 (5 × 10^–6 M) was 49 ± 15% (n = 4) after 3 min. A maximal EM-523 -stimulation reduced a subsequent ACh response by 78 ± 7%, whereas EM-523 and ME-34 could not induce a contraction after ACh.We conclude that motilides depend upon external Ca²⁺ to a similar extent to motilin. Like motilin, they are also able to mobilize intracellular Ca Z + stores. Our results support the hypothesis that motilides act on motilin receptors. Send offprint requests to T. L. Peeters at the above address