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Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than approximately 650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of approximately 650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation may considerably affect their distribution and dynamics.

Herbal remedies from the Indian subcontinent have been found to have high concentrations of heavy metals and unsupervised treatment may result in toxicity. We report the case of an Indian patient with hepatitis who was found to have lead poisoning where the source was traced to ethnic remedies he had been taking for diabetes.

A reversed-phase high-performance liquid-chromatographic method for the simultaneous determination of retinol, alpha-tocopherol, alpha-carotene, beta-carotene, cryptoxanthin, lutein/zeaxanthin, and lycopene is described. This method was applied to plasma measurements in healthy young and elderly subjects. The plasma, deproteinized with ethanol, is extracted twice with n-hexane. After evaporation, the residue is dissolved in 50 microL of tetrahydrofuran and made up to 200 microL with ethanol. Samples (50 microL) are injected onto a 250 x 4.6 mm column of 5-microns-particle Spherisorb ODS1 (Phase Separations) that had been equilibrated with solvent mixture A:B (90:10 by vol) [A = 100 mmol/L ammonium acetate in methanol: acetonitrile (80:20 by vol) and B = 100 mmol/L ammonium acetate in water] at 2 mL/min. The analytes are eluted by running a 12-min linear gradient to 100% A; solvent A is then maintained for 10 min. Intrabatch CVs were 2.3%, 3.3%, 2.8%, 3.6%, 3.6%, and 3.0% for retinol, alpha-tocopherol, lutein/zeaxanthin, cryptoxanthin, lycopene, and beta-carotene, respectively. The corresponding interbatch CVs were 4.9%, 5.8%, 12.3%, 6.5%, 8.0%, and 3.4%.

Thrombolysis is effective in treating patients with acute myocardial infarction when started within 12 h of onset, and thus is in widespread use. Early diagnosis is essential but some patients admitted to the coronary care unit with myocardial infarction do not meet the diagnostic criteria on arrival, and thus do not undergo thrombolysis. We studied 117 patients admitted consecutively to our coronary care unit with suspected but unproven myocardial infarction; normally none would have received thrombolytic agents. In each patient creatine kinase levels were measured on admission and after intervals by nurses using capillary blood samples and a dry chemistry system. Infarction was subsequently confirmed in 29 patients. Of these, 17 (59%) were correctly diagnosed and underwent thrombolysis within 12 h on the basis of a raised creatine kinase measured at the bedside. Our findings suggest that use of a bedside assay by nurses allows additional patients with myocardial infarction to receive the benefit of thrombolytic therapy within the first 12 h.

This prospective double blind randomised seven day crossover controlled clinical trial was carried out to determine whether enterally fed patients with moderately impaired gastrointestinal function require a predigested nitrogen (N) source compared with whole protein. Twelve malnourished patients with varying gastrointestinal abnormalities, who required enteral feeding, received 2.25 l of one of two isocaloric isonitrogenous enteral diets (1 kcal/ml, 4.8 g nitrogen/l) containing either predominantly medium chain peptides (tetra or higher peptides) or whole protein as the nitrogen source. Nitrogen absorption and balance were calculated from dietary intake and analysis of 24 hour total urinary and faecal nitrogen for the last five days of each study period. There was no significant difference in either stool weight (110 (SEM) (49) v 111 (32) g/d), nitrogen absorption (91 (2) v 89 (2)%) or nitrogen balance (+1.0 (1.3) v +0.6 (1.4) g nitrogen/d) between the peptide and whole protein nitrogen sources when all patients are considered. There was, however, evidence to suggest a nutritional advantage from administering an enteral diet whose nitrogen source comprises oligopeptides, rather than whole protein, to a subgroup of patients with small bowel disease.

Glycine has been regarded as a poor source of nitrogen for total parenteral nutrition. Two prospective randomised cross over controlled clinical trials were undertaken to compare the efficacy of high and low glycine containing amino acid solutions in parenterally fed malnourished hypoalbuminaemic patients with gastrointestinal disease. In the first study (n = 9), amino acid solutions in which glycine accounted for 23% and 4% of total nitrogen were compared. No statistically significant difference was found in urea nitrogen/total urinary nitrogen excretion (mean (SEM) 83.4 (1.4) v 81.6 (1.7)%, p = 0.31), nitrogen balance (-1.9 (2.4) v -0.6 (2.0) g/day, p = 0.31) or plasma protein concentrations and blood urea nitrogen. In the second extended study (n = 5), there was no significant difference in net whole body protein synthesis (+1.3 (4.7) v-0.2 (3.7) mg/kg/hour, p = 0.69) or fractional (0.403 (0.070) v 0.480 (0.41)%/hour, p = 0.68) and absolute albumin synthesis rates (6.0 (0.9) v 7.2 (0.06) mg/kg/hour, p = 0.22), on comparing solutions of 25% and 8% glycine nitrogen. In addition, a significantly higher proportion of total urinary nitrogen comprised urea when patients received the low glycine containing amino acid source (81.4 (2.5) v 83.8 (3.2)%, p = 0.04). It is concluded that there are no apparent short term nutritional or metabolic disadvantages to using amino acid solutions that contain up to 25% of nitrogen as glycine in total parenteral nutrition.

In a case/control study, serum concentrations of vitamins A and E and major carotenoids were determined in patients with Alzheimer's disease, multi-infarct dementia and control subjects. The results showed that both Alzheimer's and multi-infarct dementia patients had significantly lower levels of vitamin E and beta-carotene than controls (vitamin E: 18.65 +/- 3.62 mumol/l in Alzheimer's disease and 15.80 +/- 6.93 mumol/l in multi-infarct dementia versus 30.03 +/- 12.03 mumol/l in controls; beta-carotene less than 0.13 to 0.42 mumol/l in Alzheimer's disease and less than 0.13 to 0.30 mumol/l in multi-infarct dementia versus 0.13 to 1.53 mumol/l in controls). Vitamin A was significantly reduced only in the Alzheimer's patients (1.56 +/- 0.78 mumol/l in Alzheimer's disease versus 2.13 +/- 0.86 mumol/l in controls).

The effect of sulphasalazine and olsalazine on jejunal and ileal water and electrolyte absorption was investigated in normal subjects by a steady state intestinal perfusion of a physiological glucose bicarbonate electrolyte solution in the absence and presence of increasing concentrations of each drug. (Olsalazine 0.25 g/l, 1.0 g/l, jejunum; 0.5 g/l, 1.0 g/l, ileum; sulphasalazine 0.25 g/l, 0.5 g/l, 2.0 g/l jejunum; 1.0 g/l, 2.0 g/l, ileum.) In the jejunum olsalazine at 1.0 g/l significantly inhibited water, sodium, chloride, and potassium absorption (p less than 0.05). In the ileum olsalazine at 0.5 and 1 g/l significantly inhibited glucose uptake (p less than 0.04) and water absorption (p less than 0.03). In the jejunum sulphasalazine had a dose related and significant inhibitory effect on water, bicarbonate, and sodium absorption and at 2.0 g/l an inhibitory effect on chloride, potassium (p less than 0.005), and glucose (p less than 0.05) absorption. In the ileum sulphasalazine had no significant effect on water and electrolyte absorption. All inhibitory effects were rapidly reversible. These data show that unexplained diarrhoea in patients with ulcerative colitis treated with olsalazine may occur as a consequence of inhibition of water and electrolyte absorption in the small intestine and that the mechanisms of inhibition of sulphasalazine and olsalazine are different.

A series of studies was performed to test the efficacy and safety of a parenteral lipid emulsion, Lipofundin S, when given as part of a complete nutritive mixture from the three-liter bag total parenteral nutrition (TPN) delivery system. In vitro stability studies with mixtures corresponding to high and low nutritional intakes showed the fat emulsion to be stable during refrigerated storage for at least 6 days. The clinical use of Lipofundin S in 3-liter TPN bags was studied in 39 consecutive patients requiring TPN, and there were no untoward side-effects. Nitrogen balance was maintained in patients with pancreatitis, those recovering postoperatively, and those with miscellaneous conditions. However, patients with multiple trauma remained in negative balance. The ability of sera, from patients on TPN to agglutinate Lipofundin S was compared to that from healthy controls, and acutely ill patients not on TPN. Patients on TPN showed a higher degree of in vitro creaming than acutely ill controls, and this may have been related to the severity of the underlying illness. These studies suggest that this parenteral lipid emulsion can be safely administered to patients requiring TPN when given from the 3-liter bag delivery system.

A seriously ill patient with diffuse abdominal tenderness of unknown cause is described. The diagnosis proved to be fulminating necrotizing amebic colitis with perforation. This case report serves as a reminder that amebiasis may occur in patients who have not been outside Canada, that it may readily be confused with other types of inflammatory bowel disease, and that particular care should be taken in obtaining a history of exposure. Before inflammatory bowel disease is diagnosed not only should the usual diagnostic tests such as stool examination and mucosal biopsy be done, but also serologic testing for amebiasis should be carried out.

Results of recent controlled studies show that because of difficulties in administering adequate quantities of enteral diet, positive nitrogen balance is not consistently achieved during enteral feeding. In order to determine whether nitrogen balance can be improved in routine clinical practice by prescribing enteral diets containing higher concentrations of nutrients, 118 patients with normal gastrointestinal function needing enteral nutrition were randomised to receive daily 21 of one of three polymeric diets: Standard diet (1.0 kcal/ml; 6.3 gN/l), Energy Dense diet (1.5 kcal/ml; 7.8 gN/l), and Energy-Nitrogen Dense diet (1.5 kcal/ml; 9.4 gN/l. The three diets, administered by continuous nasogastric infusion, were equally well tolerated. Results were analysed only for patients fed five or more days and who received at least 60% of prescribed enteral diet (n = 42). Positive nitrogen balance was achieved only in the patients receiving the Energy-Nitrogen Dense diet (n = 16; + 1.6 (SE) 0.6 gN/d, compared with the Standard diet (n = 12; -3.8 (1.1) gN/d; p less than 0.001), and the Energy Dense diet (m = 14; -1.9 (0.8) gN/d; p less than 0.005). As the findings of this prospective controlled trial show that positive nitrogen balance was not consistently achieved by administering 21 enteral diet containing up to 15.6 gN, consideration could, therefore, be given to routinely using enteral diets containing up to 9.4 gN/l.

A steady-state perfusion technique has been used in vivo in normal subjects to show that at concentrations occurring during therapeutic use (500 mg/1, 1.1 mmol/l) the antibiotic clindamycin reversibly inhibits bicarbonate-stimulated water and electrolyte absorption from the human jejunum. Lactose-stimulated water and electrolyte absorption was not affected by the addition of clindamycin at the same concentration. Clindamycin-induced malabsorption of water and electrolytes may contribute significantly to the diarrhoea that occurs during clindamycin therapy in the absence of pseudomembranous colitis.

The effect of jejunal infusion of glycochenodeoxycholic acid and glycocholic acid on small bowel transit time, fasting jejunal motility and serum bile acid concentrations was investigated in groups of five to six healthy subjects. Glycochenodeoxycholic acid at a concentration of 15 mmol/l (total amount: 5 mmol) and glycocholic acid 15 mmol/l (total amount: 5 mmol), both with lecithin 2.5 mmol/l, delayed (p less than 0.02) small bowel transit when compared with a bile acid free infusion [158.3 (12.5) min v 111.7 (17.6) min and 103.3 (21.8) min v 70.0 (14.9) min], inhibited (p less than 0.01 and p less than 0.05 respectively) the percentage duration of pressure activity of phase 2 [13.1 (1.8)% v 28.1 (3.4)% and 29.2 (5.5)% v 34.9 (3.9)%], but did not change duration of migrating motor complex, or of its phases. Glycochenodeoxycholic acid 10 mmol/l (total amount: 3.3 mmol), either with or without lecithin, did not delay small bowel transit significantly [145.0 (13.2) min v 115.0 (19.5) and 90.0 (11.7) min v 84.0 (8.3)]. When bile acids were infused, serum bile acid curves were similar to those obtained after a liquid meal and the peak serum bile acid concentration occurred 33.7 (6.6) min before (p less than 0.001) completion of small bowel transit. These observations suggest a role for endogenous bile acids in the regulation of small gut motility.

The metabolic response to intravenous glucagon was studied in insulin requiring diabetes before, 1 week and 1 month after treatment with insulin. The rise in plasma 3-hydroxybutyrate following glucagon in the untreated state was converted to a fall after 1 month on insulin. It is suggested that this response could provide a measure of the biological effectiveness of circulating insulin. There was no change in plasma cyclic AMP response to glucagon after treatment with insulin.

The hypothesis that the presence of glycochenodeoxycholic acid (GCDC) in the human Ileal bile acid concentrations showed a 54.0 (9.3)% absorption of glycochenodeoxycholic acid by the been tested in healthy volunteers. Mean transit times, flow rates and intraluminal pressures in a 40 cm jejunal segment proximal (n = 6) and a 40 cm ileal segment distal (n = 6) to a GCDC infusion port were measured. During GCDC infusion (60 mumol/min) jejunal and ileal transit were markedly (p less than 0.05) delayed (31.6 (7.7), mean (SEM) v 14.5 (3.8) min and 37.0 (5.7) v 21.0 (3.5) min, respectively), segment volumes increased (141.1 (30.2) v 59.2 (9.9) ml and 173.2 (26.3) v 83.9 (9.5) ml; p less than 0.05), while flow rates did not change significantly (4.6 (0.6) v 4.5 (0.6) ml/min and 4.8 (0.5) v 4.2 (0.3) ml/min, respectively). Ileal pressures (distal to the GCDC infusion port) decreased (p less than 0.05) promptly (1.0 (0.1) min) after the start of GCDC infusion. Inhibition of jejunal motility was more gradual and reached significance (p less than 0.05) only 30 min after beginning of the infusion. Ileal bile acid concentrations showed a 54.0 (9.3)% absorption of glycochenodeoxycholic acid by the 40 cm ileal segment. These observations suggest the existence of an intestinal control mechanism in healthy man, whereby presence of glycochenodeoxycholic acid in the ileum inhibits motility and delays transit in the jejunum and ileum.

Leonotis leonurus was studied with the aim of characterising nectar quality and quantity, and of monitoring the sunbirds' response to the resource. The flowers produced high quality nectar in low quantities. Nectar quality remained constant during the day and averaged 23.4% sucrose equivalents (an energy content of 3.8j/μl). Nectar production was highest during the morning when flow rates reached a peak of 3.3 μl/h. L. leonurus was visited by four species of sunbirds. In 1977 there were 7.8 visits/h to the flowers. The clump was defended by a single Olive Sunbird (Nectarinia olivacea) who defended the flowers intra- and interspecifically. On one day the territorial bird obtained approximately 57.1 kJ from the Leonotis flowers and expended 5.4 kJ on defence and 13.6 kJ overall while on the territory. Territorial behaviour and intruder pressure was a function of resource availability. When Leonotis nectar levels were high intruder pressure was intense and the territorial bird employed long chases as a defence behaviour. When nectar levels desreased intruder pressure was lower, the territorial bird chased less and employed vocalisations as a relatively inexpensive form of territorial behaviour.In 1978 there was an abundance of nectar sources in the study area due to the late onset of the dry season. Sunbirds were not territorial at Leonotis and visiting rates were lower than in 1977, averaging only 1.7 visits per hour. Instead the sunbirds concentrated on contemporaneously flowering plant species, particularly Halleria lucida.

A young woman developed an anaphylactic-type reaction during induction of anaesthesia, which was later shown to be due to suxamethonium, to which the patient had not been previously exposed. In vitro testing identified not only suxamethonium as the causative agent, but also other potentially hazardous agents, pharmacologically and chemically related to suxamethonium. Furthermore, 'unrelated' neuromuscular blocking drugs elicited no reaction from the patient's leucocytes, suggesting that in future anaesthesia these agents may be used with little risk. The leucocytes of the patient's parents and brother were also tested, the brother showing a minimal positive reaction. Skin testing confirmed the significance of the in vitro histamine release by the patient's leucocytes.

The role of sunbirds (Nectariniidae) in the pollination ecology of Strelitzia nicolai (Musaceae) was studied for one year in a coastal dune forest in Zululand, South Africa. It was found that S. nicolai produced large quantities of low quality nectar (1.74 j/μl); that nectar production was highest during the day-time; and that the flowers displayed several characteristics attractive to bird-visitors. The flowers were large, conspicuous and provided the birds with a perch, facilitating easy access to the nectar. Flowers were visited by four species of sunbirds: Olive Sunbird Nectarinia olivacea, Grey Sunbird N. veroxii, Black Sunbird N. amethystina, and Collared Sunbird Anthreptes collaris. Sunbirds visited the flowers throughout the year, and apparently cued into changes in the flower angle as an indication of nectar flow rates. Sunbirds perched on the flowers in a manner which effected pollination, the pollen being transferred to the stigma via the birds' feet. Besides the sunbirds, there were other visitors (bushbabies, monkeys and insects) to the flowers, but they did not visit the flowers frequently nor did they appear to be significant pollinators. The high seed set of S. nicolai in the study area attests to the efficacy of the sunbirds as pollinators.

Mouth-to-cecum transit and serum bile acid profile after ingestion of a lactulose-labeled liquid meal (440 kcal) were measured in eight patients with gallstones and a radiologically functioning gallbladder before and three to five months after cholecystectomy and in 15 controls. In the patients mouth-to-cecum transit was longer after the operation, 87.5 +/- 18.5 (mean +/- SEM) min vs 57.5 +/- 9.7 min (P less than 0.05). Mouth-to-cecum transit times before and after the operation were not different from controls (58.0 +/- 6.7 min). Serum bile acid AUCs were similar (P = NS) in patients and controls, while total bile acid and cholylglycine fasting concentrations were higher after cholecystectomy (P less than 0.05 and P less than 0.01 respectively). Cholecystectomy prolongs mouth-to-cecum transit of a liquid meal.

An automated method of chemiluminescence analysis of nitrogen used routinely for 4 yr. Liquid samples (urine, enteral, and parenteral feeds) required simple dilution, whereas feces required a modified acid-digestion procedure, before analysis. For urine samples, the coefficient of variation was within batch from 0.9-3.6%, and between batch 4.3-7.6%. At a sample injection rate of 2 microliter/sec, the useful dynamic range, for urine diluted 1:200, was 0-14 g N/liter. Precision for fecal nitrogen analysis was 3.8-6.7% for samples of low to high nitrogen content. The correlation between this technique and an established Kjeldahl method for fecal analysis was studied (r = 0.96, slope = 1.30). The discrepancy between the methods was due to inefficient conversion of nitrogen to NH4+ during Kjeldahl digestion of feces, rather than systematic errors in chemiluminescence analysis. Reliability was as good as for other automated clinical analyzers and sample cost was ca. 0.22 pounds. It has proved possible to analyze approximately 80 samples in the working day. The efficiency of measuring 24-hr urine urea-nitrogen (UUN) and total urine nitrogen (TUN) in patients on general wards was measured. Results were obtained on 87% of TPN days, but large variations were noted in UUN/TUN from less than 30% to greater than 90% (average 75.7%) in patients receiving TPN, and from less than 55% to 100% (average 83.8%) in patients receiving enteral nutrition. In contrast, UUN/TUN was 87.0% and 84.0% in healthy subjects, fasted or receiving iv nutrition, respectively. We therefore expect that clinical nutritionists will find increasing applications for this method of nitrogen analysis.

The present study questions the concept of routinely using 'starter regimens' at the outset of enteral feeding with chemically defined elemental diets. A hypertonic elemental diet with an osmolality of 630 mOsm/kg was administered by 24-hr nasogastric infusion to 12 patients with exacerbations of inflammatory bowel disease and to two patients with short bowel syndrome. Starter regimens were not used. Upper gastrointestinal symptoms of nausea, abdominal bloating, and colicky pain occurred transiently in only five of 14 patients. Stool frequency did not increase during full-strength feeding, and daily stool weights decreased significantly (p less than 0.01). These findings show that it is safe to administer undiluted hypertonic elemental diets by constant nasogastric infusion to patients with inflammatory bowel disease. Avoiding starter regimens leads to increased nutrient intake and improved nitrogen balance.