Radiation-epidemiological studies of thyroid cancer incidence among children and adolescents in the Bryansk oblast of Russia after the Chernobyl accident (1991–2001 follow-up period)

In this study, thyroid cancer incidence (follow-up period: 1991–2001) has been analyzed, including persons who were exposed as children at an age between 0 and 17 years and who are living in the Bryansk oblast, the worst contaminated area of Russia after the Chernobyl accident. According to the census of 1989, the population of this oblast comprises 375 thousand people. Thyroid doses from incorporated radioiodine isotopes—both for the thyroid cancer cases and the study population—were determined based on the official methodology approved by the Russian Scientific Commission on Radiation Protection. Between 1991 and 2001, a total of 199 thyroid cancer cases were diagnosed at cancer centers (the so-called oncological dispensaries) of the investigated regions. The performed analysis relies on medical and dosimetric information available from the Russian National Medical and Dosimetric Registry which was established after the Chernobyl accident. Diagnoses were confirmed histologically for 95% of the cases. The analysis described revealed statistically significant radiation risk only for those exposed as children at an age of 0–9 years. In this group, the standardized incidence ratio (the national incidence rate was used as a reference) in the considered time period is estimated to be 6.7 (5.1, 8.6 95%CI) and 14.6 (10.3, 20.2 95%CI) for girls and boys, respectively. The risk dependence on age at exposure has also been studied. It has been shown that the smaller the age the higher the risk. For girls whose age at exposure was 0–4 years, the excess relative risk per 1 Gy for the period 1991–2001 was 45.3 (5.2, 9,953 95%CI; with internal control) and 28.8 (4.3, 2,238 95%CI; with external control), respectively. For boys whose age at exposure was 0–9 years the corresponding excess relative risk per 1 Gy was 68.6 (10.0, 4,520 95%CI) and 177.4 (−276, 10⁶ 95%CI), respectively. Dependence of radiation risk on time was studied, with the focus on two follow-up periods 1991–1996 and 1997–2001, respectively. In 1997–2001 the radiation risk is shown to decrease among girls, and increase among boys.     

The effects of temperature, altitude and latitude on the arrival and departure dates of the swallow Hirundo rustica in the Slovak Republic

The (barn) swallow Hirundo rustica is a traditional harbinger of spring in many countries of the Northern Hemisphere. This paper uses information on the arrival and departure dates of the swallow in the Slovak Republic for the 30 years 1961–1985 and 1996–2000. Records were taken at 19 locations throughout the Republic representing an altitude range from 105 m to 760 m. Monthly temperature data were constructed from six meteorological stations. With the use of regression techniques, trends towards later arrival, earlier departure and the effects of latitude, altitude and temperature are all apparent. Received: 25 October 2000 / Revised: 23 April 2001 / Accepted: 23 April 2001     

Childhood leukemia in Belarus before and after the Chernobyl accident

Childhood leukemia (ICD 204–208 [1]) incidence rates in the different regions of Belarus are reported for a period before and after the Chernobyl accident (1982–1994). There are, at this point, no recognizable trends towards higher rates.     

Thyroid cancer risk in Belarus after the Chernobyl accident: Comparison with external exposures

Within the time period 1990–1993, childhood thyroid cancer incidence due to the Chernobyl accident increased dramatically in Belarus, especially with regard to the birth cohort January 1, 1971, to May 31, 1986. This rise subsequently slowed down, i.e. during the period 1994–1996. The respective data were analysed and compared with the results of an analysis on the time dependence of thyroid cancer incidence in a pooled cohort of persons who had been exposed during childhood to external radiation with high dose rates. Concerning the period of 5–10 years following exposure, the excess absolute cancer risk per unit thyroid dose in the latter (external) exposure group was found to exceed the one in the Belarus group by a factor of two. This difference, however, is not statistically significant. The age-adjusted average excess absolute risk per unit thyroid dose for the period of 5–50 years following external childhood exposure was found to be 8 female and 14 male cases per 10⁴ person-year · Gy, which is a factor about 2.5 times higher than for the non-adjusted risk in the pooled cohort, as reported by Ron et al. in 1995. Assessments of future excess thyroid cancer cases due to the Chernobyl accident were done on the basis of the time dependence of thyroid cancer risk following external exposure. The thyroid cancer incidence among the birth cohort considered in Belarus and for a period starting from the cessation of the available observation data (1 January 1997) and extending to 50 years after the Chernobyl accident has been estimated to be about 15,000 cases, with an uncertainty range of 5000–45,000 cases. According to our calculations, 80% of these cases exceed the baseline risk under enhanced thyroid surveillance. Received: 8 June 1999 / Accepted in revised form: 20 November 1999     

On the detection of dynamic responses in a drought-perturbed tropical rainforest in Borneo

The dynamics of aseasonal lowland dipterocarp forest in Borneo is influenced by perturbation from droughts. These events might be increasing in frequency and intensity in the future. This paper describes drought-affected dynamics between 1986 and 2001 in Sabah, Malaysia, and considers how it is possible, reliably and accurately, to measure both coarse- and fine-scale responses of the forest. Some fundamental concerns about methodology and data analysis emerge. In two plots forming 8 ha, mortality, recruitment, and stem growth rates of trees ≥10 cm gbh (girth at breast height) were measured in a ‘pre-drought’ period (1986–1996), and in a period (1996–2001) including the 1997–1998 ENSO-drought. For 2.56 ha of subplots, mortality and growth rates of small trees (10–<50 cm gbh) were found also for two sub-periods (1996–1999, 1999–2001). A total of c. 19 K trees were recorded. Mortality rate increased by 25% while both recruitment and relative growth rates increased by 12% for all trees at the coarse scale. For small trees, at the fine scale, mortality increased by 6% and 9% from pre-drought to drought and on to ‘post-drought’ sub-periods. Relative growth rates correspondingly decreased by 38% and increased by 98%. Tree size and topography interacted in a complex manner with between-plot differences. The forest appears to have been sustained by off-setting elevated tree mortality by highly resilient stem growth. This last is seen as the key integrating tree variable which links the external driver (drought causing water stress) and population dynamics recorded as mortality and recruitment. Suitably sound measurements of stem girth, leading to valid growth rates, are needed to understand and model tree dynamic responses to perturbations. The proportion of sound data, however, is in part determined by the drought itself. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phylogenetic Position of Mammoth and Steller's Sea Cow Within Tethytheria Demonstrated by Mitochondrial DNA Sequences

Here we report DNA sequences from mitochondrial cytochrome b gene segments (1,005 base pairs per species) for the extinct woolly mammoth (Mammuthus primigenius) and Steller's sea cow (Hydrodamalis gigas) and the extant Asian elephant (Elephas maximus), the Western Indian manatee (Trichechus manatus), and the hyrax (Procavia capensis). These molecular data have allowed us to construct the phylogeny for the Tethytheria. Our molecular data resolve the trichotomy between the two species of living elephants and the mammoth and confirm that the mammoth was more closely related to the Asian elephant than to the African elephant. Our data also suggest that the sea cow–dugong divergence was likely as ancient as the dugong–manatee split, and it appears to have been much earlier (22 million years ago) than had been previously estimated (4–8 million years ago) by immunological comparison. Received: 8 August 1996 / Accepted: 30 September 1996     

Climate-driven warming during spring destabilises a Daphnia population: a mechanistic food web approach

Temperature-driven changes in interactions between populations are crucial to the estimation of the impact of global warming on aquatic food webs. We analysed inter-annual variability in two data sets from Bautzen reservoir, Germany. In a long-term data set (1981–1999) we examined the pelagic phenology of Daphnia galeata, a keystone species, the invertebrate predator Leptodora kindtii, phytoplankton and Secchi depth in relation to water temperature and the North Atlantic Oscillation index. In a short-term data set (1995–1998) we examined food web relations, particularly the consumption of D. galeata by young-of-the-year (YOY) percids and L. kindtii and rates of population change of D. galeata (abundance, recruitment pattern and non-consumptive mortality). The start of the clear-water stage (CWS) was correlated with winter temperatures. It started 5.8 days earlier per degree warming after warm winters (mean January–March temperature ≥2.5°C) compared to cold winters (mean temperature <2.5°C). However, the end of the CWS remained relatively constant. Predation by L. kindtii and YOY percids on D. galeata started distinctly earlier, i.e. by 13.0 and 6.5 days per degree warming, respectively, in years when the average May temperature was high (≥14°C) compared to years when it was low (<14°C). Significant reductions of Daphnia abundance in midsummer occurred only in years in which the mean May temperature exceeded 14°C. This temperature regime resulted in a match of over-exploitation of food resources by Daphnia during the CWS and strong predation by YOY percids and L. kindtii. Consumptive mortality increased at higher rates with a rise in temperature than net recruitment, resulting in lower Daphnia densities at the end of the CWS. Our data suggest that even low warming by 1.7°C during a short, but critical seasonal period, resulting in the coincidence of two or more factors adversely affecting a keystone species, such as Daphnia, may induce changes in whole lake food webs and thus alter entire ecosystems. Priority programme of the German Research Foundation—contribution 9.     

RAAS gene polymorphisms influence progression of pediatric hypertrophic cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is a disease with variable rate of progression. Young age is an independent risk factor for poor outcome in HCM. The influence of renin–angiotensin–aldosterone (RAAS) genotype on the progression of HCM in children is unknown. Children with HCM (n = 65) were enrolled prospectively across two centers (2001–2005). All subjects were genotyped for five RAAS gene polymorphisms previously associated with LV hypertrophy (pro-LVH): AGT M235T, ACE DD, CMA-1903 A/G, AGTR1 1666 A/C and CYP11B2-344 C/T. Linear regression models, based on maximum likelihood estimates, were created to assess the independent effect of RAAS genotype on LV hypertrophy (LVH). Forty-six subjects were homozygous for <2 and 19 were homozygous for ≥2 pro-LVH RAAS polymorphisms. Mean age at presentation was 9.6 ± 6 years. Forty children had follow-up echocardiograms after a median of 1.5 years. Indexed LV mass (LVMI) and LV mass z-scores were higher at presentation and follow-up in subjects with ≥2 pro-LVH genotypes compared to those with <2 (P < 0.05). Subjects with ≥2 pro-LVH genotypes also demonstrated a greater increase in septal thickness (IVST) and in LV outflow tract (LVOT) obstruction on follow-up (P < 0.05). On multivariate analysis, a higher number of pro-LVH genotypes was associated with a larger effect size (P < 0.05). Pro-LVH RAAS gene polymorphisms are associated with progressive septal hypertrophy and LVOT obstruction in children with HCM. Identification of RAAS modifier genes may help to risk-stratify patients with HCM. This work was presented in part at the Annual Scientific Sessions of the American Heart Association, New Orleans, November 2004.     

Growth and Development in Wild Owl Monkeys (<Emphasis Type="Italic">Aotus azarai</Emphasis>) of Argentina

Life history predicts that in sexually dimorphic species in which males are the larger sex, males should reach sexual maturity later than females (or vice versa if females are the larger sex). The corresponding prediction that in sexually monomorphic species maturational rates will differ little between the sexes has rarely been tested. We report here sex differences in growth and development to adulthood for 70 female and 69 male wild owl monkeys (Aotus azarai). In addition, using evidence from natal dispersal and first reproduction (mean: 74 mo) for 7 individuals of known age, we assigned ages to categories: infant, 0–6 mo; juvenile, 6.1–24 mo; subadult, 24.1–48 mo; adult >48 mo. We compared von Bertalanffy growth curves and growth rates derived from linear piecewise regressions for juvenile and subadult females and males. Growth rates did not differ between the sexes, although juvenile females were slightly longer than males. Females reached maximum maxillary canine height at ca. 2 yr, about a year earlier than males, and females’ maxillary canines were shorter than males’. Thus apart from canine eruption and possibly crown–rump length, the development of Azara’s owl monkeys conforms to the prediction by life history that in monomorphic species the sexes should develop at similar paces.     

Polymorphism of the <Emphasis Type="Italic">cox1</Emphasis> mtDNA gene from cercarial isolates of the avian schistosome <Emphasis Type="Italic">Bilharziella polonica</Emphasis> (Trematoda: Schistosomatidae) from Belarussian lakes

We have studied the phylogeographic structure of avian schistosomes Bilharziella polonica (Trematoda: Schistosomatidae), parasites of 18 molluscs Planorbarius corneus (family Planorbidae) from three Belarussian lakes. Low nucleotide (π < 0.5%) and high haplotype (h = 85.6%) diversity of the gene encoding the cytochrome C oxidase first subunit (cox1) was found on the part of the species range studied. The phylogenetic reconstructions showed that the sample examined consists of at least two lineages of haplotypes, A and C. Haplotype diversity was somewhat higher in lineage C. The genetic divergence between these genealogical lines reached 0.55%, while the time of possible divergence was 180000–270000 years. Possible evolutionary scenarios for differentiation of the B. polonica lines and effectiveness of using cox1 for barcoding trematode populations and finding coevolutionary parasite-host relationships are discussed.     

137Cs mobility in soils and its long-term effect on the external radiation exposure

To predict the external gamma-dose rate of Chernobyl-derived ¹³⁷Cs for a period of about 100 years after its deposition, the vertical distribution of radiocesium in several meadow soils in the Chernobyl area and in Germany was determined, and the corresponding residence half-times of this radionuclide in the various soil layers were evaluated using a compartment model. The resulting residence half-times were subsequently used to calculate the vertical distribution of ¹³⁷Cs in the soil as a function of time and finally to predict the external gamma-dose rates in air for these sites at various times. A regression analysis of the data obtained showed that the time dependence of the relative gamma-dose rate in air D(t) at the Chernobyl sites can be described by an exponential equation D(t) = a + b ⋅ exp(–t/c), where t is the time after deposition. For the ten German sites the best fit was obtained using the two-exponential equation D(t) = a ⋅ exp(–t/b) + c ⋅ exp(–t/d). The gamma-dose rate of ¹³⁷Cs at the Chernobyl sites decreases significantly more slowly with time than at the German sites. This means that after e.g. 30 years the mean relative gamma-dose rate at the German sites will have decreased from 100% (corresponding to an infinite plane source on a smooth surface) to 9% (95% confidence interval 8%–10%), while at the sites in the Chernobyl area it will have decreased only to 21% (20%–23%). This difference is the result of the longer residence half-times of ¹³⁷Cs in the soils at the Chernobyl sites. All results are compared with estimates from earlier studies. Received: 16 October 1996 / Accepted in revised form: 28 November 1996     

Barrai’s parameters for the Kirov oblast population and their geographic distribution

The distribution of surnames in for populations of the district rank in Kirov oblast has been used to calculate Barrai’s parameters, which are the following: I _r, 0.0008–0.0208; H, 6.80-211.57; ν, 0.003–0.058; α, 47.35–1191.39; R, 23.03–50.07. The results have been compared with data on the 1980s; no substantial changes in the studied parameters during a generation have been found.     

A new species: Gerres microphthalmus (Perciformes: Gerreidae) from Japan with notes on limited distribution, included in the “G. filamentosus complex”

 Gerres microphthalmus sp. nov., described on the basis of the holotype and 38 paratypes, has a limited distribution in Japan, including Tanega Island, southeastern Kyushu, southern Shikoku, and southern Kii Peninsula, central Honshu. It has not been recorded from the Ryukyu Islands. The species is the fourth member of the “G. filamentosus complex,” characterized by an elongated second dorsal fin spine, the others being G. filamentosus, G. infasciatus, and G. macracanthus. Gerres microphthalmus sp. nov. is most similar to G. filamentosus in overall body appearance, but differs from the latter in having smaller eyes (8%–11% of standard length vs. 10%–16% in the latter), a higher orbit diameter ratio (as % of snout length) (93%–143% of snout vs. 71%–104% of snout), and fewer pored lateral line scales (40–43 vs. 43–46). The limited distribution pattern of the new species is discussed with G. equulus and Lates japonicus (Centropomidae) having a limited distribution similar to that of the new species. Received: June 28, 2001 / Revised: November 13, 2001 / Accepted: December 10, 2001     

Features of the reproductive ecology of the rock catfish Silurus lithophilus

Some aspects of the reproductive ecology of the rock catfish Silurus lithophilus (Siluriformes: Siluridae), a species endemic to the Lake Biwa system, were investigated from April to July in 1989–1994. Field observations were conducted at a rocky shoal, which was also a spawning ground of S. biwaensis, along the shore of the Seta River, the lake's outlet. Spawning of S. lithophilus occurred around midnight at shallow, rocky places on the shoal (5–70 cm in water depth) from early May to mid-July, starting earlier than S. biwaensis (mid-May to mid-July). Spawning tended to occur at low water temperatures irrespective of high-water events, unlike S. biwaensis, and in low densities (fewer than 8 fish per night) compared to S. biwaensis (1–45 fish per night). Although the rock catfish tended to appear and spawn at higher frequencies on nights when S. biwaensis spawned or appeared, it always avoided conflict with the latter species by spawning at sites far from those used by S. biwaensis or after S. biwaensis had left the vicinity. The survival of eggs of S. lithophilus might be favored by a strategy of diverting predator attention from them by synchronizing spawning nights with S. biwaensis. Received: February 27, 2001 / Revised: October 17, 2001 / Accepted: November 8, 2001     

Early ontogeny of Lophonectes gallus (Bothidae) from southeastern Australia

 The early ontogeny of Lophonectes gallus (Bothidae) is described based on 83 specimens (1.9–17.5 mm BL), collected from the Tasman Sea off southeastern Australia. The larvae are diagnosed by the following array of characters: vertebrae 10 + 30–31 = 40–41; one elongated dorsal fin ray and several melanophores present on gut in preflexion stage (1.9–4.7 mm BL); and spines on posterior basipterygial process, and urohyal, cleithrum, and epiotic without spines after postflexion stage (8.0–17.5 mm BL). The larvae are relatively small at metamorphosis (15–18 mm BL) compared with other bothid larvae. Received: March 22, 2001 / Revised: December 12, 2001 / Accepted: December 26, 2001     

Upeneus australiae, a new goatfish (Mullidae: Perciformes) from Australia

 Upeneus australiae sp. nov. is described on the basis of 14 specimens collected from Australian waters. Although it belongs to the seven-spined group of Upeneus, now comprising five species, U. australiae is distinguished from its congeners by the combination of the following characters: 6–7 + 16–18 (modally 7 + 17) gill rakers, ectopterygoids without teeth, five and six black oblique bars on upper and lower caudal lobes, respectively, and peritoneum transparent with small black spots. Received: July 26, 2001 / Revised: November 2, 2001 / Accepted: December 4, 2001     

Growth of larval and juvenile Diaphus theta (Pisces: Myctophidae) in the transitional waters of the western North Pacific

Diaphus theta is one of the most common myctophid fish species in the subarctic and transitional waters of the North Pacific. The growth of larval and juvenile D. theta was investigated using sagittal otolith increment analysis of specimens caught in transitional waters of the western North Pacific. Samples taken over a 24-h period demonstrated that otoliths exhibited daily growth cycles, allowing accurate determination of age. Calcification of the incremental zone of otoliths took place only at night, suggesting that the formation cycle of the increment of juvenile D. theta was different from that of shallow-water fishes and would be related to their diel vertical migration. The relationships between standard length (SL) and daily growth increment (D) were expressed as linear equations: SL = 2.65 + 0.141D (r ² = 0.942) for larvae of 5.1–9.6 mm SL and SL = 3.54 + 0.129D (r ² = 0.933) for juveniles of 13.7–27.6 mm SL. The growth rates were 0.14 mm d⁻¹ in larvae and 0.13 mm d⁻¹ in juveniles; this is slow compared with tropical or subtropical mycto-phid species, in which growth occurs at about twice these rates. The larval period, including the metamorphic stage, was long compared with species at lower latitudes and was estimated to be 71 days. The slow growth rate and long period of larval stage of D. theta would be the life history pattern of high-latitudinal species adapted to a low-temperature habitat. Received: March 23, 2001 / Revised: July 5, 2001 / Accepted: July 19, 2001     

Epidemiological features and resistance pattern in uropathogens isolated from chronic bacterial prostatitis

Chronic bacterial prostatitis (CBP) is, usually, caused by uropathogens, especially gram-negative bacilli, although infection is sometimes due to Gram-positive and atypical microorganisms. A recent increasing in prevalence of Gram-positive strains has been reported. The aim of this study was to explore the epidemiological features and resistance rates in uropathogens isolated from CBP outpatients in last 10 years. All consecutive outpatients with demonstrated CBP attending a single Sexually Transmitted Disease centre from January 1997 and December 2008, were enrolled and underwent microbiological cultures in first void early morning urine, midstream urine, expressed prostatic secretion, and post prostate massage urine. Prevalence of different bacterial strains was stratified in four different periods: 1997–1999, 2000–2002, 2003–2005, 2006–2008. Any changes observed in epidemiological features and resistance rates in uropathogens over the whole study period have been analyzed. The present study has been planned, thus, as in vitro study. From 6,221 patients, 4,601 Gram-positive and 1,620 Gram-negative bacterial strains have been isolated. Enterococcus faecalis and Escherichia coli strains are the first and second frequent pathogens found, respectively. Significant differences between E. faecalis prevalence in the 1997–1999 and 2006–2008 periods were found. E. coli showed a significant difference between prevalence in 1997–1999 and 2006–2008 periods. Gram-positive organisms showed a decreasing of susceptibility to ciprofloxacin as well as Gram-negative strains, while a good susceptibility to the levofloxacin was evidenced. E. faecalis prevalence seemed to be raised in 2006–2008 periods. Moreover, a decreasing of activity of ciprofloxacin and a good activity profile of levofloxacin have been reported.     

Genome-wide meta-analysis for rheumatoid arthritis

Meta-analysis is being increasingly used as a tool for integrating data from different studies of complex phenotypes, because the power of any one study to identify causal loci is limited. We applied a novel meta-analytical approach (Loesgen et al. in Genet Epidemiol 21(Suppl 1):S142–S147, 2001) in compiling results from four studies of rheumatoid arthritis in Caucasians including two studies from NARAC (Jawaheer et al. in Am J Hum Genet 68:927–936, 2001; Jawaheer et al. in Arthritis Rheum 48:906–916, 2003), one study from the UK (MacKay et al. in Arthritis Rheum 46:632–639, 2001) and one from France (Cornelis et al. in Proc Natl Acad Sci USA 95:10746–10750, 1998). For each study, we obtained NPL scores by performing interval mapping (2 cM intervals) using GeneHunter2 (Kruglyak et al. in Am J Hum Genet 58:1347–1363, 1996; Markianos et al. in Am J Hum Genet 68:963–977, 2001). The marker maps differed among the three consortium groups, therefore, the marker maps were aligned after the interval mapping was completed and the NPL scores that were within 1 cM of each other were combined using the method of Loesgen et al. (Genet Epidemiol 21(Suppl 1):S142–S147, 2001) by calculating the weighted average of the NPL score. This approach avoids some problems in analysis encountered by using GeneHunter2 when some markers in the sample are not genotyped. This procedure provided marginal evidence (P<0.05) of linkage on chromosome 1, 2, 5 and 18, strong evidence (P<0.01) on chromosomes 8 and 16, and overwhelming evidence in the HLA region of chromosome 6.     

Long-term treatment with recombinant interferon alpha-2b prolongs survival of asymptomatic HIV-infected individuals

Rationale and objective: Early long-term treatment with recombinant interferon (IFN) alpha-2b delayed disease progression in asymptomatic Human Immunodeficiency Virus (HIV) carriers in a randomized trial that lasted from October 1987 to February 1992 (14). The aim of the work reported in this paper was to observe if there was also an effect on survival when the same patients were followed-up further. Design and interventions: IFN alpha-2b was given 3 × 10⁶ IU, 3 times weekly. The control group did not receive any treatment. The main end-point for this evaluation was death due to any cause. The deadline was August 1995. Population: Subjects were anti-HIV-1 seropositive, Western blot-confirmed, asymptomatic (CDC group II), or with generalized lymphadenopathies (CDC group III). The groups had 79 (control) and 83 (IFN) patients. Main results: Mean survival was longer in the IFN group (95% CI: 127–152 vs. 101–120 months since infection or 80–90 vs. 70–82 months since the start of treatment). Survival rates were higher in IFN-treated individuals (61–77% vs. 24–54% at 10 years of infection or 53–69% vs. 34–52% at 7 years of treatment or follow-up). It was also confirmed that disease progression is significantly slower in IFN-treated patients. There were 23.4 vs. 3.2% long-term survivors in the IFN and control groups, respectively (p=0.005). IFN-treated patients had fewer AIDS-related malignancies (5 vs. 11), mainly Kaposi’s sarcomas (1 vs. 5). This difference was not statistically significant, but clinically interesting. There was no difference in survival if measured since the onset of AIDS. Conclusion: IFN alpha treatment given from the early stages of infection, but not after the appearance of AIDS symptoms, can prolong survival.