Different responses to changes in phosphorus,P, among lakes. A study of slopes in chl-a = f(P) graphs

The least squares estimator of a linear regression coefficient _L will give an overall expression for the change in with x. In fresh water ecology, however, subgroups, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaSGaci% 4Aaaaa!37BE!\[P\operatorname{k}\], of a parent population may have slopes which differ from the overall slope, _L. By constructing frequency histograms for the set of angles: Arctang % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4uaSGaam% yAaiaadQgaaaa!38AE!\[\operatorname{S} ij\],% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4uaSGaam% yAaiaadQgaaaa!38AE!\[\operatorname{S} ij\]= para sa y and x% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiaadM% faliaadMgakiabgkHiTiaadMfaliaadQgakiaacMcacaGGVaGaaiik% aiaadIhaliaadMgakiabgkHiTiaadIhaliaadQgakiaacMcaaaa!42F0!\[(Yi - Yj)/(xi - xj)\], i < j, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiEaSGaam% yAaOGaeyiyIKRaamiEaSGaamOAaaaa!3BAB!\[xi \ne xj\], peaks in the distribution may be identified and related to ecological phenomenon. To identify peaks we fit Gaussian distributions to the frequency histograms. For a set consisting of 142 observations of chlorophyll-a and total phosphorus (nutrient) concentrations (TP) from 16 lakes we found four Gaussian peaks corresponding to four subgroups, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaSGaci% 4Aaaaa!37BE!\[P\operatorname{k}\]k = 1,4. One group identified a response of chl-a to changes in TP which correspond approximately to the average slope found by least square regression (the slope was 0.49). The second group consisted of steeper response than the average (1.28). A third group showed that there is an enhanced proportion of cases where chl-a does not respond to TP (zero slope, all the three deep lakes > 10 m, included in the date set contributed to this group). The size of the last group, spanning a wide range of slopes, suggested that about 30% of the inter annual changes in chl-a is unrelated to TP. The results are compared to result obtained by simple least squares regression and to the Theil non-parametric slope estimator.     

Cohort study of predictive value of urinary albumin excretion for atherosclerotic vascular disease in patients with insulin dependent diabetes.

OBJECTIVE: To examine whether slightly elevated urinary albumin excretion precedes development of atherosclerotic vascular disease in patients with insulin dependent diabetes independently of conventional atherogenic risk factors and of diabetic nephropathy. DESIGN: Cohort study with 11 year follow up. SETTING: Diabetes centre in Denmark. SUBJECTS: 259 patients aged 19-51 with insulin dependent diabetes of 6-34 years'' duration and without atherosclerotic vascular disease or diabetic nephropathy at baseline. MAIN OUTCOME MEASURES: Baseline variables: urinary albumin excretion, blood pressure, smoking habits, and serum concentrations of total cholesterol, high density lipoprotein cholesterol, sialic acid, and von Willebrand factor. End point: atherosclerotic vascular disease assessed by death certificates, mailed questionnaires, and hospital records. RESULTS: Thirty patients developed atherosclerotic vascular disease during follow up of 2457 person year. Elevated urinary albumin excretion was significantly predictive of atherosclerotic vascular disease (hazard ratio 1.06 (95% confidence interval 1.02 to 1.18) per 5 mg increase in 24 hour urinary albumin excretion, P = 0.002). Predictive effect was independent of age; sex; blood pressure; smoking; serum concentrations of total cholesterol, high density lipoprotein cholesterol, sialic acid, and von Willebrand factor; level of haemoglobin A(lc); insulin dose, duration of diabetes, and diabetic nephropathy (hazard ratio 1.04 (1.01 to 1.08) per 5 mg increase     

Predictors of mortality in insulin dependent diabetes: 10 year observational follow up study.

OBJECTIVE: To evaluate the prognostic significance of microalbuminuria and overt diabetic nephropathy and other putative risk factors for cardiovascular and all cause mortality in insulin dependent diabetes. DESIGN: Ten year observational follow up study. SETTING: Outpatient diabetic clinic in a tertiary referral centre. SUBJECTS: All 939 adults with insulin dependent diabetes (duration of diabetes five years or more) attending the clinic in 1984; 593 had normal urinary albumin excretion (< or = 30 mg/24 h), 181 persistent microalbuminuria (31-299 mg/24 h), and 165 overt nephropathy (> or = 300 mg/24 h). MAIN OUTCOME MEASURE: All cause and cardiovascular mortality. RESULTS: Fifteen per cent of patients (90/593) with normoalbuminuria, 25% (45/181) with microalbuminuria, and 44% (72/165) with overt nephropathy at baseline died during follow up. Cox multiple regression analysis identified the following significant predictors of all cause mortality: male sex (relative risk 2.03; 95% confidence interval 1.37 to 3.02), age (1.07; 1.06 to 1.08), height (0.96; 0.94 to 0.98), smoking (1.51; 1.09 to 2.08), social class V versus social class IV (1.70; 1.25 to 2.31), log10 urinary albumin excretion (1.45; 1.18 to 1.77), hypertension (1.63; 1.18 to 2.25), log10 serum creatinine concentration (8.96; 3.34 to 24.08), and haemoglobin A1c concentration (1.11; 1.03 to 1.20). Age, smoking, microalbuminuria, overt nephropathy, and hypertension were significant predictors of cardiovascular mortality. Mortality in patients with microalbuminuria was only slightly increased compared with that in patients with normoalbuminuria. Median survival time after the onset of overt diabetic nephropathy was 13.9 years (95% confidence interval 11.8 to 17.2 years). CONCLUSIONS: Abnormally increased urinary albumin excretion and other potentially modifiable risk factors such as hypertension, smoking, poor glycaemic control, and social class predict increased mortality in insulin dependent diabetes. Microalbuminuria by itself confers only a small increase in mortality. The prognosis of patients with overt diabetic nephropathy has improved, probably owing to effective antihypertensive treatment.     

Drug induced changes in cardio-vascular parameters in the Atlantic cod,Gadus morhua

Summary Ventral (VAP) and dorsal (DAP) aortic blood pressure, heart rate (HR) and cardiac output ( ) were recorded simultaneously in unanaesthetized Atlantic cod, and the effects of vasoactive drugs on the cardio-vascular parameters studied. Mean resting values for the parameters were VAP=4,39 kPa, DAP=2,49 kPa, HR=41 beats/min, and = 29,1 ml/min×kg. Adrenaline constricted the systemic vasculature, dilated the branchial vasculature and caused a decrease of HR and due to a cholinergic reflex. After atropine pre-treatment this reflex was abolished, and the effect of adrenaline on blood pressure enhanced. A small decrease in persisted after atropine, presumably reflecting the effect of an increased end-systolic afterload.Phenylephrine produced a weak increase in systemic vascular resistance, while isoprenaline lowered both systemic and branchial vascular resistance. The effect of isoprenaline is probably mediated by beta adrenoceptors in both vascular beds, since propranolol antagonizes the effect.Acetylcholine in low doses produces a drop in without affecting HR, while higher doses also stop the heart. There is no significant change in either branchial and systemic vascular resistance after acetylcholine.Abbreviations VAP mean ventral aortic blood pressure - DAP mean dorsal aortic blood pressure - TBPD trans-branchial blood pressure drop - HR heart rate - SV stroke volume - cardiac output (ventral aortic blood flow) - VR _g branchial vascular resistance - VR _s systemic vascular resistance     

Sympathetic nervous control of blood flow in the gills of the Atlantic cod,Gadus morhua

Summary The effects of sympathetic nerve stimulation, adrenaline and isoprenaline on the inflow pressure and efferent arterial and venous flow rates were studied in a cod gill preparation perfused at constant flow rate.The dominant effect of adrenaline was a reduced inflow pressure, accompanied by an increase in arterial flow and a decrease in venous flow. Isoprenaline also decreased the inflow pressure, but the changes in both outflow rates were small or absent.Sympathetic nerve stimulation gave arterial and venous flow changes comparable to the adrenaline effects, but the inflow pressure increased during nerve stimulation. Propranolol has little effect on the nerve responses, but phentolamine abolished or reversed the increase in inflow pressure, and also decreased or abolished the changes in outflow rates.The possible sites of action of the sympathetic fibres, and the distribution of adrenoceptors in the effector tissue is discussed. It is concluded that the main effect of sympathetic nerve stimulation is -adrenoceptor mediated, involving constriction of the arterio-venous pathway. The-adrenoceptor mediated control of total branchial vascular resistance may largely depend on circulating catecholamines.     

Influence of Diet on Experimental Swine Dysentery. 1. Effects of A Vitamin E and Selenium Deficient Diet Supplemented with 6.8 % Cod Liver Oil

Sixteen growing pigs were fed a vitamin E and selenium deficient diet; half of the animals (Group 2) were given a daily supply of vitamin E and selenium. After having been fed these diets for 53 days, the pigs were infected orally with minced colonic material from cases with typical swine dysentery. This exposure resulted in outbreaks of swine dysentery in both groups. The incubation times were, however, distinctly shorter and the clinical symptoms much more pronounced in Group 1 than in Group 2. The patho^morphological lesions in the colon also differed between the 2 groups. In the pigs of Group 1 evident pseudomembraneous lesions were observed in the spiral colon. In Group 2, the colonic alterations consisted predominantly of a catarrhal enteritis; pseudomembranes occurred in a minor part of colon in only 4 pigs. Both the clinical and the chemical observations and the pathological findings indicated a much better vitamin E and selenium balance in the pigs of Group 2. It is concluded that the treatment with vitamin E and selenium in Group 2 greatly increased resistance to swine dysentery.     

The reactivity of affinity labels: A kinetic study of the reaction of alkyl halides with thiolate anions—a model reaction for protein alkylation

Factors have been investigated which govern the electrophilic reactivity of alkyl halides with thiolate anions in aqueous solution. In the series of alkyl halides studied, some are potential metal-directed affinity labels, while others are frequently used in protein modification. Previous data on the kinetics of this type of alkylation are compared with the present results. The influence of electronic, polar, and steric factors on alkyl halide reactivity is seen. The following order of reactivity for alkyl halides bearing different α substituents was observed: RCH₂CH(X)COOCH₃ > RCH₂CH(X)CONH₂ > RCH₂CH(X)COOH > RCH₂CH₂X > RCH₂CH(X)CH₂OH. The metal-directed affinity labels are imidazole derivatives, some of which have substituents in their imidazole ring. The effect of the imidazole ring and of ring substitution on reactivity is seen. The nucleophilic reactivity of thiols is highly pH dependent since the thiolate anion (RS^?) is the reactive species, but only minor differences emerged between different free thiolates.     

Electron Microscopic Changes in Colon in Experimental Swine Dysentery

Colonic lesions in experimental swine dysentery were studied electron microscopically. Changes indicative of stasis were commonly observed in the microcirculatory vessels of lamina propria. Early lesions in epithelial cells included sparse, short and irregular microvilli, swollen and degenerated mitochondria, and swelling and vesiculation of endoplasmatic reticulum. Numerous large spirochaetes were observed in these locations: a) in the crypts, b) free (i.e. not membrane bound) in cytoplasm of damaged epithelial cells, and c) in cavities, around vessels of lamina propria. It is suggested that stasis, and resultant disturbances in microcirculation in early developmental stages of swine dysentery, may play a pathogenetic role in the development of the necrotic colonic lesions. Finally, it is discussed whether a mechanism related to Sanarelli-Shwartzman reaction is implicated in the development of colonic lesions in swine dysentery.