Nitrous oxide: emission from soils during nitrification of fertilizer nitrogen.

Nitrous oxide is released from soils to the atmosphere during nitrification of ammonium and ammonium-producing fertilizers under aerobic conditions as well as by denitrification of nitrate under anaerobic conditions. Emissions of nitrous oxide during nitrification of fertilizer nitrogen may be significant in regard to the potential threat of fertilizer-derived nitrous oxide to the stratospheric ozone layer. Such emissions can be greatly reduced through the use of nitrapyrin, which inhibits nitrification of ammonium by soil microorganisms.

Conjugal thyroid disease--six couples with thyrotoxicosis, one couple with hypothyroidism, and one couple with thyroid cancer.

Six married couples with thyrotoxicosis, one couple with primary hypothyroidism, and one couple with well differentiated thyroid cancer are reported. The occurrence of conjugal thyroid disease raises the possibility that environmental factors may have played an aetiological role.

Primary thyroid lymphoma: clinical features, treatment and outcome: a report of 8 cases.

AIM: To assess the clinical findings and response to treatment of patients with primary thyroid lymphoma. METHODS: Patients with primary thyroid lymphoma were identified by reviewing the diagnoses of all patients with thyroid malignancies diagnosed at Christchurch Hospital between 1980-91. The records of patients with primary thyroid lymphoma were abstracted. RESULTS: During the 12 year period eight patients (6 females, 2 males) with primary thyroid lymphoma were diagnosed and treated. The median age was 78 years (range 18-90 yr). All patients presented with recent thyroid masses and obstructive symptoms were prominent. Two patients were initially referred with endocrine dysfunction--one thyrotoxic and one hypothyroid. Six patients had nonHodgkin lymphoma and two Hodgkin's disease, with all having stage IA disease. Two patients were treated by thyroidectomy, and in the remaining six patients the thyroid lymphoma masses regressed following radiotherapy with the two youngest patients also receiving chemotherapy. At follow up all five elderly patients have since died--two of disseminated lymphoma, two of concurrent cancers and one of vascular disease, and the three younger patients remain in remission after 4.5, 6.5 and 10.5 years. CONCLUSION: Primary thyroid lymphoma usually presents with obstructive symptoms, but there may be associated thyroid dysfunction. Thyroid lymphoma masses respond well to radiotherapy.

Elimination of the adverse effects of urea fertilizer on seed germination, seedling growth, and early plant growth in soil.

The rapidly increasing importance of urea fertilizer in world agriculture has stimulated research to find methods of reducing the problems associated with the use of this fertilizer. One of these problems is that urea has adverse effects on seed germination, seedling growth, and early plant growth in soil. Because there is evidence that these adverse effects are caused largely, if not entirely, by ammonia produced through hydrolysis of urea fertilizer by soil urease, we explored the possibility that they could be reduced or eliminated by amending urea fertilizer with a small amount of a urease inhibitor. Studies with seeds of alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), rye (Secale cereale L.), sorghum [Sorghum bicolor (L.) Moench], and wheat (Triticum aestivum L.) showed that phenylphosphorodiamidate and N-(n-butyl)thiophosphoric triamide were the most effective of 10 urease inhibitors evaluated for reduction of the adverse effect of urea on seed germination. N-(n-butyl)-thiophosphoric triamide was superior to phenylphosphorodiamidate for reducing the adverse effects of urea solutions on seed germination and seedling growth in soil, and it completely eliminated the adverse effect of urea granules on early plant growth in soil. The data reported indicate that the adverse effects of urea fertilizer on seed germination, seedling growth, and early plant growth in soil could be eliminated or markedly reduced by amending the fertilizer with as little as 0.01% (wt/wt) of N-(n-butyl)thiophosphoric triamide.

Effects of Mn2+ and Mg2+ on assimilation of NO3- and NH4+ by soil microorganisms.

Although it has been demonstrated that Mn2+ and Mg2+ can influence the activity of glutamine synthetase in various organisms, there is little information concerning the effects of these cations on the activity of this enzyme in soil microorganisms or on ability of these microorganisms to assimilate NO3- and NH4+. We studied the effects of different concentrations of Mn2+ and Mg2+ on assimilatory NO3- reduction and NH4+ assimilation in cultures of two microorganisms commonly found in soil [Pseudomonas fluorescens (ATCC 13525) and Azotobacter chroococcum (ATCC 9043)] and in an enrichment culture of soil microorganisms. We found that Mn2+ strongly inhibited NH4+ assimilation by soil microorganisms and blocked the inhibitory effect of NH4+ on assimilatory NO3- reductase (ANR) activity, thereby uncoupling ANR activity from nitrogen assimilation and causing the NH4+ formed by ANR activity to be released to the environment. Mg2+ counteracted the effect of Mn2+ on microbial metabolism of nitrogen, which suggests that the overall effect of these cations on nitrogen assimilation by soil microorganisms will depend on the ratio of their concentrations in soil.

Regulation of assimilatory nitrate reductase activity in soil by microbial assimilation of ammonium.

It is well established that assimilatory nitrate reductase (ANR) activity in soil is inhibited by ammonium (NH4+). To elucidate the mechanism of this inhibition, we studied the effect of L-methionine sulfoximine (MSX), an inhibitor of NH4+ assimilation by microorganisms, on assimilatory reduction of nitrate (NO3-) in aerated soil slurries treated with NH4+. We found that NH4+ strongly inhibited ANR activity in these slurries and that MSX eliminated this inhibition. We also found that MSX induced dissimilatory reduction of NO3- to NH4+ in soil and that the NH4+ thus formed had no effect on the rate of NO-3 reduction. We concluded from these observations that the inhibition of ANR activity by NH4+ is due not to NH4+ per se but to products formed by microbial assimilation of NH4+. This conclusion was supported by a study of the effects of early products of NH4+ assimilation (L amino acids) on ANR activity in soil, because this study showed that the biologically active, L isomers of glutamine and asparagine strongly inhibited ANR activity, whereas the D isomers of these amino acids had little effect on ANR activity. Evidence that ANR activity is regulated by the glutamine formed by NH4+ assimilation was provided by studies showing that inhibitors of glutamine metabolism (azaserine, albizziin, and aminooxyacetate) inhibited ANR activity in soil treated with NO3- but did not do so in the presence of MSX.

Inhibition of assimilatory nitrate reductase activity in soil by glutamine and ammonium analogs.

Recent work in our laboratory indicated that the inhibitory effect of ammonium (NH4+) on assimilatory nitrate reductase (ANR) activity in soil is not due to NH4+ per se but to glutamine formed by microbial assimilation of NH4+. To test this conclusion, we studied the effects of eight analogs of L-glutamine (L-glutamic acid gamma-methyl ester, L-glutamic acid gamma-hydrazide, L-glutamic acid gamma-hydroxamate, L-glutamic acid gamma-ethyl ester, L-glutamic acid dimethyl ester, L-asparagine, L-aspartic acid beta-methyl ester, and L-aspartic acid beta-hydroxamate) and two analogs of ammonium (hydroxylamine and methylamine) on ANR activity in soil slurries. The studies with the L-glutamine analogs showed that all except L-glutamic acid dimethyl ester inhibited ANR activity in soil. The sharp contrast observed between the strong inhibitory effect of L-glutamic acid gamma-methyl ester on ANR activity and the complete lack of an inhibitory effect with the corresponding dimethyl ester suggests that only the free-acid form of glutamine effectively inhibits ANR activity. The studies with hydroxylamine and methylamine showed that both of these ammonium analogs inhibited ANR activity in soil and that this inhibition was dependent upon glutamine synthetase activity. This dependence indicates that inhibition of ANR activity by hydroxylamine and methylamine was due to formation of the glutamine analogs L-glutamic acid gamma-hydroxamate and L-glutamic acid gamma-methylamide, respectively. These observations support the conclusion that the inhibitory effect of NH4+ on ANR activity in soil is due to glutamine formed by microbial assimilation of NH4+.

Staging laparotomy in Hodgkin's disease.

A surgeon's experience in staging laparotomy for Hodgkin's disease over an eight-year period is reviewed. The laparotomies concerned were the vast majority of such staging procedures done in this regional centre over this period. A relatively large series of staging operations performed by one surgeon has thus been accumulated and demonstrates the value of experience, and in the light of the allows questioning of the need for some of the steps considered to be basic to staging laparotomy. In the 19 cases reviewed, staging laparotomy altered the method of management in 44%.

Arthritis and hypogammaglobulinaemia. A. Family survey.

1. Hypogammaglobulinaemic patients admitted to the Medical Research Council's immunoglobulin therapy trials up to 1963 were examined for evidence of arthritis and were compared with population samples from Leigh, Wensleydale and Watford which were used as controls. 2. Four out of 60 males had inflammatory polyarthritis compared with an expected 0.4. In addition, 3 had synovitis limited to the knees and 4 had had polyarthritis in the past, the expected figures being 0.12 and 2.4 respectively. None of the patients had definite rheumatoid arthritis as defined by the American Rheumatism Association Criteria, though one satisfied the New York Criteria for Still's disease. All were seronegative and none of the patients with polyarthritis had radiological evidence of arthritis. None of the 18 female patients had arthritis. The prevalence of arthritis of synovitis in males was 29% in 1964, but in the following 3 years varied between 8 and 11%, suggesting a strong environmental influence. 3. All of the 7 males with inflammatory polyarthritis had levels of IgG, IgA, IgM and IgD, which were less than 30% of the standard normals and steatorrhoea was present in three. Steatorrhoea was also noted in 2 of 5 patients wih arthritis who died before the start of the survey, compared with 7% of all the males. 4. Clinical inflammatory polyarthritis was no more common in the first-degree relatives of patients with hypogammaglobulinaemia than in the population as a whole and they had no excess of erosive arthritis visible in X-rays of the hands or feet nor was sacro-iliitis excessively frequent. 5. Positive tests for rheumatoid factor were found in only 2 of the patients with hypogammaglobulinaemia and the first-degree relatives had no more positive sheep cell agglutination or latex fixation tests than expected in random population samples. 6. It is concluded that the seronegative polyarthritis which occurs in patients with hypogammaglobulinaemia is unrelated genetically to rheumatoid arthritis or Still's disease.

Evidence that the adverse effect of urea fertilizer on seed germination in soil is due to ammonia formed through hydrolysis of urea by soil urease.

Studies using seeds of wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) indicated that the adverse effect of urea fertilizer on seed germination in soil is due to ammonia formed through hydrolysis of urea by soil urease and is not due to urea itself, to urea fertilizer impurities such as biuret, or to nitrite formed by nitrification of urea nitrogen. Support for this conclusion was obtained from (i) comparison of the effects on seed germination in soil of purified urea, urea fertilizers, urea fertilizer impurities, and compounds formed by enzymatic and microbial transformations of urea in soil; (ii) studies showing that ammonia volatilized from soils treated with urea completely inhibited germination of seeds close to, but not in contact with, these soils; and (iii) experiments showing that the adverse effect of urea fertilizer on seed germination in soil was completely eliminated when the soil was autoclaved to destroy urease or was treated with phenylphosphorodiamidate to inhibit soil urease activity before treatment with urea fertilizer.

Production of nitrous oxide by ammonia-oxidizing chemoautotrophic microorganisms in soil.

Gas chromatographic studies showed that nitrous oxide was produced in each instance when sterilized (autoclaved) soil was incubated after treatment with ammonium sulfate and inoculation with pure cultures of ammonia-oxidizing chemoautotrophic microorganisms (strains of Nitrosomonas, Nitrosospira, and Nitrosolobus). Production of N(2)O in ammonium-treated sterilized soil inoculated with Nitrosomonas europaea increased with the concentration of ammonium and the moisture content of the soil and was completely inhibited by both nitrapyrin and acetylene. Similar effects of nitrapyrin, acetylene, ammonium concentration, and soil moisture content were observed in studies of factors affecting N(2)O production in nonsterile soil treated with ammonium sulfate. These observations support the conclusion that, at least under some conditions, most of the N(2)O evolved from soils treated with ammonium or ammonium-producing fertilizers is generated by chemoautotrophic nitrifying microorganisms during oxidation of ammonium to nitrite.

Toxic autonomous thyroid nodule following neck irradiation.

A 37-year-old male with a history of neck irradiation in childhood presented with thyrotoxicosis due to an autonomous thyroid nodule. Adjacent to the nodule was a radiation scar from radiotherapy administered 35 years previously. Hemithyroidectomy was performed and histological examination excluded malignant change. Long term follow-up should continue to detect possible nodule formation in the contralateral lobe.

Potential phytotoxicity associated with the use of soil urease inhibitors.

Recent work in our laboratory showed that the adverse effect of urea fertilizer on seed germination and seedling growth in soil is due to ammonia produced through hydrolysis of urea by soil urease (NH(2)CONH(2) + H(2)O --> 2NH(3) + CO(2)) and can be eliminated by amending the fertilizer with a small amount of a urease inhibitor such as N-(n-butyl)thiophosphoric triamide or phenylphosphorodiamidate. Continuation of this work showed that these inhibitors can induce leaf-tip necrosis in plants. Research to account for this phytotoxicity indicated that it resulted from an accumulation of toxic amounts of urea in plants through inhibition of urease activity by N-(n-butyl)thiophosphoric triamide and phenylphosphorodiamidate. Support for this conclusion was provided by experiments showing that these urease inhibitors increased both leaf-tip necrosis and urea concentrations in wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor(L.) Moench] plants grown in soils treated with urea and that the necrotic areas of such plants had a much higher concentration of urea than did the nonnecrotic areas. The potential of urease inhibitors for inducing phytotoxicity should not preclude their use to eliminate the adverse effects of urea fertilizers on seed germination and seedling growth in soil because the ammonia produced through hydrolysis of urea fertilizer by urease is much more detrimental to plant growth than is the urea accumulation induced by urease inhibitors.

Phytotoxicity of foliar-applied urea.

Recent work in our laboratory showed that the adverse effect of urea fertilizer on seed germination and seedling growth in soil is due to ammonia produced through hydrolysis of urea by soil urease (NH(2)CONH(2) + H(2)O --> 2NH(3) + CO(2)) and can be eliminated by amending the fertilizer with a small amount of a urease inhibitor such as phenylphosphorodiamidate. Because the leaf-tip necrosis often observed after foliar fertilization of plants with urea is usually attributed to ammonia formed through hydrolysis of urea by plant urease, we studied the possibility that this necrosis could be eliminated or reduced by adding phenylphosphorodiamidate to the urea fertilizer. We found that, although addition of this urease inhibitor to foliar-applied urea increased the urea content and decreased the ammonia content and urease activity of soybean [Glycine max. (L.) Merr.] leaves fertilized with urea, it increased the leaf-tip necrosis observed after fertilization. We conclude that this necrosis resulted from accumulation of toxic amounts of urea rather than from formation of toxic amounts of ammonia. This conclusion was supported by our finding that the necrotic areas of soybean leaves treated with urea or with urea and phenylphosphorodiamidate contained much higher concentrations of urea than did the nonnecrotic areas.