Utilizing associational resistance for biocontrol: impacted by temperature, supported by indirect defence.

BACKGROUND: Associational herbivore resistance is potentiated by neighbouring heterogenic plant species that impact a focal plant's attraction to herbivores or the damage that they cause. One mechanism to confer associational resistance is believed to be exposure to neighbour-emitted volatiles, the receivers of which range from intra- and interspecific neighbour plants to higher-trophic-level insects. In previous studies the passive adsorption of neighbour-emitted semivolatiles has been reported, but little is known regarding the mechanisms and ecological consequences on the receiver plant and its associated biota. To utilize volatile-based associational resistance for agricultural applications, it is imperative to know its effectiveness under varying diurnal temperatures and whether herbivore natural enemies, providing biological control, are impacted. Mimicking varying diurnal temperatures in a laboratory set-up, we assessed how the tritrophic model system Brassica oleracea var. italica (broccoli)-Plutella xylostella (crucifer specialist herbivore)-Cotesia vestalis (endoparasitoid of P. xylostella) is influenced by exposure to the natural semivolatile emitter plant Rhododendron tomentosum Harmaja. RESULTS: Rhododendron tomentosum-exposed B. oleracea was less susceptible to P. xylostella oviposition at both night-time (12°C) and day-time (22°C) temperatures and less favoured and damaged by P. xylostella larvae at 12°C. Exposure did not interfere with indirect defence, i.e. attraction of the natural enemy C. vestalis on host-damaged, R. tomentosum-exposed B. oleracea under 22°C, while there was a reduction in attraction (marginal preference towards host-damaged B. oleracea) under 12°C. CONCLUSIONS: The ability of R. tomentosum exposure to render associational resistance against an agriculturally important Brassica herbivore P. xylostella without severely compromising the specialist parasitoid C. vestalis host location encourages further studies on the potential of using this naturally abundant plant for biocontrol. The generality of our finding on temperature as a potential regulating mechanism for the efficacy of semivolatile emitter-based associational resistance towards specialist pest larval damage should be further studied in natural and agricultural associations. Our study emphasizes the need to develop techniques to compare volatiles at the leaf versus air interface and associate their appearance and ecological role with times of activity and level of specialisation of herbivores and their natural enemies.

The effect of warming and enhanced ultraviolet radiation on gender-specific emissions of volatile organic compounds from European aspen.

Different environmental stress factors often occur together but their combined effects on plant secondary metabolism are seldom considered. We studied the effect of enhanced ultraviolet (UV-B) (31% increase) radiation and temperature (ambient +2 °C) singly and in combination on gender-specific emissions of volatile organic compounds (VOCs) from 2-year-old clones of European aspen (Populus tremula L.). Plants grew in 36 experimental plots (6 replicates for Control, UV-A, UV-B, T, UV-A+T and UV-B+T treatments), in an experimental field. VOCs emitted from shoots were sampled from two (1 male and 1 female) randomly selected saplings (total of 72 saplings), per plot on two sampling occasions (June and July) in 2014. There was a significant UV-B×temperature interaction effect on emission rates of different VOCs. Isoprene emission rate was increased due to warming, but warming also modified VOC responses to both UV-A and UV-B radiation. Thus, UV-A increased isoprene emissions without warming, whereas UV-B increased emissions only in combination with warming. Warming-modified UV-A and UV-B responses were also seen in monoterpenes (MTs), sesquiterpenes (SQTs) and green leaf volatiles (GLVs). MTs showed also a UV × gender interaction effect as females had higher emission rates under UV-A and UV-B than males. UV × gender and T × gender interactions caused significant differences in VOC blend as there was more variation (more GLVs and trans-ß-caryophyllene) in VOCs from female saplings compared to male saplings. VOCs from the rhizosphere were also collected from each plot in two exposure seasons, but no significant treatment effects were observed. Our results suggest that simultaneous warming and elevated-UV-radiation increase the emission of VOCs from aspen. Thus the contribution of combined environmental factors on VOC emissions may have a greater impact to the photochemical reactions in the atmosphere compared to the impact of individual factors acting alone.

Volatile organic compounds emitted from silver birch of different provenances across a latitudinal gradient in Finland.

Climate warming is having an impact on distribution, acclimation and defence capability of plants. We compared the emission rate and composition of volatile organic compounds (VOCs) from silver birch (Betula pendula (Roth)) provenances along a latitudinal gradient in a common garden experiment over the years 2012 and 2013. Micropropagated silver birch saplings from three provenances were acquired along a gradient of 7° latitude and planted at central (Joensuu 62°N) and northern (Kolari 67°N) sites. We collected VOCs emitted by shoots and assessed levels of herbivore damage of three genotypes of each provenance on three occasions at the central site and four occasions at the northern site. In 2012, trees of all provenances growing at the central site had higher total VOC emission rates than the same provenances growing at the northern site; in 2013 the reverse was true, thus indicating a variable effect of latitude. Trees of the southern provenance had lower VOC emission rates than trees of the central and northern provenances during both sampling years. However, northward or southward translocation itself had no significant effect on the total VOC emission rates, and no clear effect on insect herbivore damage. When VOC blend composition was studied, trees of all provenances usually emitted more green leaf volatiles at the northern site and more sesquiterpenes at the central site. The monoterpene composition of emissions from trees of the central provenance was distinct from that of the other provenances. In summary, provenance translocation did not have a clear effect in the short-term on VOC emissions and herbivory was not usually intense at the lower latitude. Our data did not support the hypothesis that trees growing at lower latitudes would experience more intense herbivory, and therefore allocate resources to chemical defence in the form of inducible VOC emissions.

A prospective study of 110 Ethiopians with thyrotoxicosis.

One hundred and ten Ethiopian thyrotoxic patients were studied between February 1986 and January 1991 in a weekly endocrine clinic of Tikur Anbessa Teaching Hospital (TATH) in Addis Ababa, Ethiopia. This gives an incidence of 22 patients per year. There were 14 males and 96 females (M:F = 1:7). Fifty three patients (48.2%) had Graves' hyperthyroidism, 37 (33.7%) toxic multinodular goitre (TMNG), 14 (12.7%) toxic adenoma, 4 (3.6%) Jodbasedow phenomenon and 2 (1.8%) had thyroiditis. The mean age was 29.2 +/- 9.8 (+/- S.D.) years for Graves' cases, 49.0 +/- 10.9 years for TMNG cases and 46.4 +/- 15.9 years for toxic adenoma cases. The clinical presentation was similar to other reported series. The majority (88.7%) of Graves' patients were below 40 years while 75.7% of TMNG patients were over 40 years of age; this is in keeping with the observed younger age incidence of Graves' hyperthyroidism and older age incidence of TMNG. All patients responded to propylthiouracil therapy and no major side effect was recognized. Nine patients underwent sub-total thyroidectomy of whom one became hypothyroid a year later. One became toxic after a year, while 6 remained euthyroid 3 years after the surgery; the other patient did not return subsequently. The result of this study shows that thyrotoxicosis is not a rare condition in Ethiopia.

The management of diabetic ketoacidosis by continuous infusion of low-dose insulin using the ordinary intravenous plastic bag and tubing.

Although the hourly intramuscular insulin regimen has been used in the management of diabetic ketoacidosis (DKA) in Ethiopia for over 7 years, continuous intravenous (IV) insulin infusion has never been previously used. In Tikur Anbessa Hospital, Addis Abeba, in 198788, we used the ordinary IV plastic bag and tubings alone to concurrently infuse the low-dose insulin and hydration solution in the management of 15 episodes of DKA in 13 patients, 5 males and 8 females. Initial blood glucose was over 400 mg/dl and urine ketones 4+ in all, and the level of consciousness ranged from drowsy to coma. Initially, 5 to 10 units of crystalline zinc insulin (CZI) was given IV directly to all but 2 patients. Then CZI was added to the normal saline IV bag and the dose of insulin was adjusted according to fluid requirements while at the same time maintaining the insulin rate at 5 to 10 units/hour until the blood glucose dropped to 250 mg/dl or lower. At this point the IV fluid was changed to 5% dextrose and the insulin infusion was reduced to 2 to 4 units/hour. The mean insulin requirement until the dextrose infusion was initiated was 33.2 +/- 7.3 units, IV fluid requirement was 3.5 +/- 0.8 litres and mean duration of treatment 4.4 +/- 1.6 hours. There was one death which was not due to insulin resistance, while all other patients fully recovered. The study demonstrates that insulin infusion using the ordinary IV plastic bag and tubings is safe, simple, and convenient in the management of DKA and hence should be used whenever indicated and feasible.

Acquired primary endocrine failure in adult Ethiopian patients.

Over a 4 year period, February 1986 to January 1990, 18 patients with acquired primary endocrine failure were seen in the weekly endocrine clinic of Tikur Anbessa teaching and referral hospital in Addis Abeba. Eight patients had hypothyroidism and 4 Addison's disease; 3 of the 5 hypothyroid and 2 of the 3 Addison's cases on whom autoantibodies were determined were positive. One patient had polyglandular failure, involving the adrenal and thyroid glands and the gonads. In one patient tuberculosis was the cause of Addison's disease and 2 patients each had hypothyroidism and hypoparathyroidism, respectively, following surgery. All the patients had clinical, hormonal and/or biochemical evidence of endocrine failure and all but the hypoparathyroid patients responded to the replacement therapy. There was one patient who had an unusual but confusing discordant hypothyroxinaemia and hypertriiodothyroninaemia who developed hypothyroidism during treatment for his Graves' disease; the hypothyroidism resolved when the medication was stopped. The results of this study indicate that autoimmune endocrine failure is probably not as rare as it was previously thought and hence further studies are recommended to find out if the incidence among Ethiopians is, indeed, similar to or different from the results in other African patients.

The pattern of thyroid diseases in adult Ethiopians and experience in management.

During the study period, between February 1986 and July 1991, a total of 373 thyroid patients (68.3% of the total endocrine cases) were seen in the weekly endocrine referral clinic of Tikur Anbessa Hospital (TAH); 258 (69.2%) came from Addis Abeba, 41 were males and 332 females (M:F = 1:8.1) and 71.9% were below 40 years of age. Thyrotoxicosis was seen in 43.7% of the patients, followed by euthyroid solitary nodules (23.6%) and simple goitres (22.3%). Euthyroid multinodular goitre was seen in 6.7% while hypothyroidism and thyroiditis were less frequent. Graves' disease was the main cause (41.7%) of thyrotoxicosis, followed by toxic multinodular goitre TMNG (31.9%), toxic solitary nodule (22.1%), Jodbasedow phenomenon (3.1%) and thyroiditis (1.2%). All thyrotoxic patients responded to the treatment, but 4 of 21 Graves' cases with relative triiodothyronine (T3) elevation relapsed after treatment was discontinued. Nine thyrotoxic patients had surgery after euthyroid state was attained; 1 each became hypothyroid and hyperthyroid a year later, 6 remained euthyroid and 1 did not return. Fine needle aspiration biopsy (FNAB) was helpful both as a diagnostic and therapeutic tool. Of 42 cystic nodules, 30 were repeatedly aspirated; 6 were cured and the rest had a reduction in size by 50%. Nine cases of solitary nodule, 3 cystic and 6 solid, were operated and the histology confirmed the cytology diagnosis in all but 1; in that one case, the cytology showed a benign lesion while the histology revealed papillary carcinoma.

A study of the transfer of insulin-requiring diabetic patients from U-40 to U-100 Lente insulin.

A pilot study of the transfer of insulin-requiring diabetic patients from U-40 to U-100 Lente insulin was conducted in 16 patients. The patients were returned to U-40 after 12 weeks on U-100. There were no adverse events specifically attributable to the process of transfer. The mean blood glucose values for the last day and the last 2 days on U-100 insulin (154.58 +/- 32.09 mg% and 152.99 +/- 29.23 mg% respectively) were significantly lower than those for the corresponding periods on U-40 insulin (178.06 +/- 38.48 mg% and 169.83 +/- 32.34 mg% respectively), (t = 2.79, p = 0.014 and t = 2.30, p = 0.036 respectively). But there was no significant difference between the mean values for the last but one day on U-40 and U-100 (152.36 +/- 27.81 vs 161.59 +/- 33.82; t = 1.16, p = 0.264). There was no significant increase in frequency (2.3 episodes per week on U40 versus 2.8 episodes per week on U-100) or severity of hypoglycaemic attacks with U-100 insulin. On the basis of this experience we feel that transfer from U-40 to U-100 insulin can be achieved without risk of serious adverse consequences provided the transfer is carried out according to a well-designed plan of action.

Glucose tolerance in adult Ethiopian patients with liver disease and porphyria cutanea tarda.

Glucose tolerance test was done in 61 patients with liver disease, 54 with porphyria cutanea tarda and 62 controls. The results showed that 45 patients (73.8%) from the liver disease group, 19 (35.2%) from the porphyria cutanea tarda (PCT) group and only 7 individuals (11.3%) from the control group had an abnormal glucose tolerance test. The differences were significant. Although nutritional state is known to influence the glucose tolerance test, we did not find any significant difference in the mean body mass index between those with an abnormal glucose tolerance test and those without in both groups of patients. Furthermore, the prevalence of an abnormal glucose tolerance test in those above and below 40 years in each group of patients was not significantly different, indicating that age probably played no significant role in this study. Therefore, glucose intolerance is common among Ethiopian patients with liver disease and PCT. As some patients with an abnormal glucose tolerance test may be expected to develop asymptomatic diabetes, we recommend that periodic blood glucose determinations should be part of the management.

Contrasting responses of silver birch VOC emissions to short- and long-term herbivory.

There is a need to incorporate the effects of herbivore damage into future models of plant volatile organic compound (VOC) emissions at leaf or canopy levels. Short-term (a few seconds to 48 h) changes in shoot VOC emissions of silver birch (Betula pendula Roth) in response to feeding by geometrid moths (Erannis defoliaria Hübner) were monitored online by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). In addition, two separate field experiments were established to study the effects of long-term foliage herbivory (FH, 30-32 days of feeding by geometrids Agriopis aurantiaria (Clerck) and E. defoliaria in two consecutive years) and bark herbivory (BH, 21 days of feeding by the pine weevil (Hylobius abietis L.) in the first year) on shoot and rhizosphere VOC emissions of three silver birch genotypes (gt14, gt15 and Hausjärvi provenance). Online monitoring of VOCs emitted from foliage damaged by geometrid larvae showed rapid bursts of green leaf volatiles (GLVs) immediately after feeding activity, whereas terpenoid emissions had a tendency to gradually increase during the monitoring period. Long-term FH caused transient increases in total monoterpene (MT) emissions from gt14 and sesquiterpene (SQT) emissions from Hausjärvi provenance, mainly in the last experimental season. In the BH experiment, genotype effects were detected, with gt14 trees having significantly higher total MT emissions compared with other genotypes. Only MTs were detected in the rhizosphere samples of both field experiments, but their emission rates were unaffected by genotype or herbivory. The results suggest that silver birch shows a rapid VOC emission response to short-term foliage herbivory, whereas the response to long-term foliage herbivory and bark herbivory is less pronounced and variable at different time points.

In vivo and in vitro hypotensive effect of aqueous extract of Moringa stenopetala.

BACKGROUND: Moringa stenopetala, Baker f. (Moringaceae) is used for food and medicine in Southern Ethiopia. OBJECTIVE: To substantiate the hypotensive effect of M. stenopetala in vivo and in vitro. METHODS: An in vivo experiment was carried out on male guinea pigs anaesthetized with pentobarbital. The arterial blood pressure was recorded from a carotid artery filled with heparinized saline via an arterial cannula connected to a pressure transducer. For the in vitro experiment the descending thoracic aorta was removed and kept moistened in Krebs-Henseleit solution and then mounted in a 20ml tissue bath maintained at 37°C and bubbled with a mixture of 95% oxygen and 5% carbon dioxide. RESULTS: Crude aqueous leaf extract of M. stenopetala caused significant fall in systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) at doses of 10, 20, 30 and 40 mg/kg in normotensive anaesthetized guinea pigs (n = 12). The effect might have been mediated by non-autonomic nervous system as the effect is not altered by atropine and propranolol. The extract also caused significant dose and time dependent inhibition of K(+) induced contraction on guinea pig aorta. CONCLUSION: M.stenopetala has blood pressure lowering effect substantiating the use of the plant in traditional medicine.