Major trends of evolution in palms

From the diversity found among palms the following evolutionary trends are suggested:habit: from sympodial to monopodial;size: from moderate toward large and also toward small;stem: from unbranched to dichotomously branched, from little to much sclerenchyma, from short to elongate internodes;leaf: from an undivided eophyll to a palmate, costapalmate, pinnately ribbed or pinnate blade; from undivided and plicate to divided along the adaxial rib (“induplicate”) or along the abaxial rib (“reduplicate”); from pinnate to bipinnate or to pinnae onceor twicedivided longitudinally; from sheath split opposite the petiole to sheath tubular; from marcescent to deciduous; from central vascular bundles of the petiole with a single phloem strand to two phloem strands;inflorescence units: from moderately branched to spicate or less frequently to more diffusely branched, from one unit per leaf axil to more than one per axil, from among the leaves to below them or to above them in a compound terminal inflorescence, from pleonanthic to hapaxanthic;prophyll: from completely to incompletely encircling the peduncle, from incompletely to completely sheathing in bud;bracts: from conspicuous to small or absent at maturity, first peduncular bract from tubular and open at the apex to completely enclosing the inflorescence in bud, and then from ungrooved to deeply plicate;flower arrangement: from solitary, pedicellate, bracteolate flowers to a sympodial cincinnus of 2 or 3 or more, or to a short monopodial axis of 2–4 or more;bracteoles: from sheathing and prophyllate to completely closed or to incompletely developed or absent;flowers: from bisexual to unisexual, then associated with polygamy or monoecism to dioecism;perianth: from trimery to dimery or tetramery to decamery or to reduced and monochlamydeous;sepals: from distinct and imbricate to connate or separated;petals: from distinct and imbricate to valvate, or strongly imbricate, or connate; from small and ovate to large and variously shaped, or to small;stamens: from 6 to 3 or to more than 6 (to 950+);filaments: from relatively slender and distinct to broad and thick, and often connate or adnate to the perianth or both;staminodes: from stamenlike with abortive anthers only, to short teeth, or to a cupule at the base of the ovary, or to absent;pollen: from monosulcate to trichotomosulcate to dicolpate to monocolpate, diporate, or triporate;gynoecium: from apocarpous to syncarpous, from thin walls to thick, variously specialized walls;carpels or locules: from 3 to 2-1 or to 4–10;ovules: from moderate to small or to large, from anatropous to hemianatropous to campylotropous to orthotropous;pistillode: from only slightly modified from the gynoecium to vestigial or lacking or rarely to prominent;fruit: from fleshy to dry and fibrous;endocarp: from little differentiated or thin, to thick and hard, and sometimes with a pore or operculum over the embryo;seed: from moderate to small or to very large, from entire to dissected, bilobed, or perforate;endosperm: from homogeneous to invaginated or ruminate;germination: from remotetubular or -ligular to adjacent-ligular;chromosome complement: fromn = 18 ton = 17, 16, 15, 14, 13.     

The sequence of electron carriers in the reaction of cytochromec oxidase with oxygen

Kinetic studies of the electron transfer processes performed by cytochrome oxidase have assigned rates of electron transfer between the metal centers involved in the oxidation of ferrocytochromec by molecular oxygen. Transient-state studies of the reaction with oxygen have led to the proposal of a sequence of carriers from cytochromec, to Cu_A, to cytochromea, and then to the binuclear (i.e., cytochromea ₃-Cu_B) center. Electron exchange rates between these centers agree with relative center-to-center distances as follows; cytochromec to Cu_A 5–7 Å, cytochromec to cytochromea 20–25 Å, Cu_A to cytochromea 14–16 Å and cytochromea to cytochrome a₃-Cu_B 8–10 Å. It is proposed that the step from cytochromea to the binuclear center is the key control point in the reaction and that this step is one of the major points of energy transduction in the reaction cycle.     

Oviduct binding ability of porcine spermatozoa develops in the epididymis and can be advanced by incubation with caudal fluid

The sperm reservoir is formed when spermatozoa bind to the epithelium of the uterotubal junction and caudal isthmus of the oviduct. It is an important mechanism that helps synchronize the meeting of gametes by regulating untimely capacitation and polyspermic fertilization. This study investigated the influence of epididymal maturation and caudal fluid on the ability of spermatozoa to bind to oviduct epithelium using a model porcine oviduct explant assay. Spermatozoa from the rete testis, middle caput (E2-E3), middle corpus (E6), and cauda (E8) of Large White or Large White × Landrace boars aged 10 to 14 months were diluted in modified Androhep solution and incubated with porcine oviduct explants. Results reported in this study support our hypothesis that testicular spermatozoa need to pass through the regions of the epididymis to acquire the ability to bind to the oviduct. There was a sequential increase in the number of spermatozoa that bound to oviduct explants from the rete testis to caudal epididymis. Binding of caudal spermatozoa to isthmic explants was the highest (15.0 ± 1.2 spermatozoa per 1.25 mm², mean ± standard error of the mean; P ≤ 0.05) and lowest by spermatozoa from the rete testis (2.0 ± 0.3 per 1.25 mm²), and higher to isthmus from sows compared to gilts (35.8 ± 6.7 per 1.25 mm² vs. 14.8 ± 3.0 per 1.25 mm²; P ≤ 0.05). Binding of ejaculated spermatozoa to porcine isthmus was higher than that for caudal spermatozoa (26.3 ± 1.4 per 1.25 mm² vs. 15.0 ± 0.8 per 1.25 mm²; P ≤ 0.05) and higher to porcine than to bovine isthmus (26.3 ± 2.3 per 1.25 mm² vs. 18.8 ± 1.9 per 1.25 mm²; P ≤ 0.05). Incubation of spermatozoa from the caput and corpus in caudal fluid increased the ability of spermatozoa to bind to the oviduct epithelium (P ≤ 0.05). In conclusion, the capacity of testicular spermatozoa to bind to the oviduct epithelium increases during their maturation in the epididymis and can be advanced by components of the caudal fluid.     

Ecological Risk Assessment and Quantitative Consequence Analysis

Ecological risk actually refers to two separate things. First, risk to the environment as a result of human activity. Contaminated sites are an example. Second, risk to the biota—flora, fauna, and people—as a result of environmental hazards. Geophysical risk arising from natural hazards is an example. Risk is a combination of likelihoods and consequences. This article examines methods used to quantify the consequences. At the general level, such methods are linked to the methods used to quantify the likelihoods and thus to quantify the risks. It is possible to use the existing frameworks of risk management, health risk assessment, and ecological risk analysis to develop a risk management framework that is suitable for ecological risk assessment. The framework consists of the following steps:

1. Determine concernsby using risk assessment techniques for various scenarios.

2. Identify the consequences by systematically identifying hazards.

3. Undertake calculations by using relevant models.

4. Evaluate certainties, uncertainties, and probabilities involved in the calculations of the vulnerability and of the exposure.

5. Compare with criteriato assess the need for further action.

6. Determine and act on options to control, mitigate, and adapt to the risk.

7. Communicatethe results to those who need to know.

     

Bioassay studies on the reaction of Aedes aegypti & Aedes albopictus (Diptera: Culicidae) on different attractants

BackgroundThe studies on mosquito attractants had been develop intensively in the recent years. However, the study on fruit peel extract as mosquito attractant was scarce, even though various fruits had demonstrated the ability to attract different types of mosquito species.ObjectiveThis study aims to determine the potential of Carica papaya (papaya) and Ananas comosus (pineapple) peel extracts to attract Aedes albopictus and Aedes aegypti.MethodsThe Aedes mosquitoes response to the fruit peel extracts were conducted in the no-choice and choice assay using modified olfactometer. The Preference Index (PI) in each assay was calculated and arcsine transformed before conducting independent t–test to determine the significant different between the mean arcsine transformed PI and the tested hypothesis mean PI.ResultNo choice assay indicate both Aedes species have significant attraction to the papaya and pineapple peel extracts (p < 0.05). In choice assay, Ae. albopictus is revealed to equally attracted to the papaya and pineapple peel extracts (p > 0.05) while Ae. aegypti is significantly attracted to the papaya peel extract (p < 0.05).ConclusionThe study had identified that both fruit peel extracts able to attract Aedes mosquitoes with Ae. albopictus is equally attracted to papaya and pineapple peel extracts while Ae. aegypti is more attracted to the papaya peel extract than the pineapple peel extract.     

Isopropanol enhancement of carbon tetrachloride metabolism in vivo

We examined the effects of isopropanol (ISOP) pretreatment on the metabolism of ¹⁴CCl₄ to ¹⁴CO₂ and CHCl₃ exhaled in the breath, to ¹⁴C metabolite excreted in 24 hr urine and feces from 0 to 24 hr, and to ¹⁴C metabolite bound to liver at 24 hr. Fasted male rats were given 0.1 or 2.0 mmoles ¹⁴CCl₄/kg. ISOP pretreatment, which markedly enhanced the hepatotoxicity of CCl₄, selectively enhanced the rate and total extent of ¹⁴CO₂ and CHCl₃ metabolite exhalation. The pathways of CCl₄ metabolism leading to CO₂ and CHCl₃ metabolite formation may be more relevant to the hepatotoxicity of CCl₄ than the pathways leading to urinarym fecal or covalently bound metabolites.     

Comparative studies of zinc metabolism in cultured chinese hamster cells with differing metallothionein-induction capacities

Previous work in our laboratory led to the isolation of a cadmium (Cd)-resistant variant (Cd^r2C10) of the line CHO Chinese Hamster cell having a 10-fold greater resistance to the cytotoxic action of Cd²⁺ compared with the CHO cell. This resistance was attributed to an increased capacity of the Cd²⁺-resistant Cd^r2C10 subline to induce synthesis of the Cd²⁺- and Zn²⁺-binding protein(s), metallothionein(s) (MT). Evidence that Cd²⁺ behaves as an analog of the essential trace metal, Zn²⁺, especially as an inducer of MT synthesis, suggested that the Cd^r and CHO cell types could be employed to investigate cellular Zn²⁺ metabolism. In the present study, measurements were made to compare CHO and Cd^r cell types for (a) growth as a function of the level of ZnCl₂ added to the culture medium, (b) uptake and subcellular distribution of Zn²⁺, and (c) capacity to induce MT synthesis. The results of these measurements indicated that (a) both CHO and Cd^r cell types grew normally (T _d≊16–18 h) during exposures to Zn²⁺ at levels up to 100 μM added to the growth medium, but displayed abrupt growth inhibition at higher Zn²⁺ levels, (b) Cd^r cells incorporate fourfold more Zn²⁺ during a 24-h exposure to the maximal subtoxic level of Zn²⁺ and (c) the CHO cell lacks the capacity to induce MT synethesis while the Cd^r cell is proficient in this response during exposure to the maximal subtoxic Zn²⁺ level. These findings suggest that (a) the CHO and Cd^r cell systems will be useful in further studies of cellular Zn²⁺ metabolism, especially in comparisons of Zn²⁺ metabolism in the presence and absence of induction of the Zn²⁺-sequestering MT and (b) a relationship exists between cellular capacity to induce MT synthesis and capacity for cellular Zn²⁺ uptake.     

Extinction times and phase transitions for spatially structured closed epidemics

This paper considers the time to extinction for a stochastic epidemic model of SEIR form without replacement of susceptibles. It first shows how previous rigorous results can be heuristically explained in terms of the more transparent dynamics of an approximating deterministic system. The model is then extended to include a host population structured into patches, with weak nearest-neighbour mixing of infection. It is shown, by considering the approximating deterministic system, that the expected time to extinction in a population of n + 1 patches each of size N is of the form a log N + bn, provided that N > N _c where N _c is a critical patch size below which transits are unlikely to occur. This corresponds to the simple decomposition of the time of an epidemic into the time it takes to spread through one patch plus the time it takes to transit to each of n successive patches. Expressions for this threshold and the coefficients of the time to extinction are given in terms of the transmission parameters of infection and the coupling strength between patches. These expressions are compared with numerical results using parameters relevant to a study of phocine distemper virus in North Sea seals, and the agreement is found to be good for large and small N. In the region when N ≈ N _c , where transits may or may not occur, interesting transitional behaviour is seen, leading to a non-monotonicity of the extinction time as a function of N.     

Functional homology of fla genes between Salmonella typhimurium and Escherichia coli

Summary Genetic studies have shown the presence of more than 20 fla genes indispensable for the formation of flagella in Salmonella typhimurium and Escherichia coli. Functional homology of the fla genes in these two bacterial species was examined through intergeneric complementation tests by bacteriophage Pl-mediated transduction from E. coli donors to S. typhimurium recipients. It was found that most of the fla gene products in these two bacterial species were interchangeable and the following correspondence was established (S. typhimurium genes vs. E. coli genes): flaFIV to flaV; flaFV to flaK; flaFVII to flaL; flaFIX to flaM; flaC to flaH; flaM to flaG; flaE to flaI; flaAI to flaN; flaAII·1 to flaB; flaAIII to flaC; flaS to flaO; flaR to flaE; flaQ to flaA; and flaB to flaR. These results suggest that the chromosomal alignment of the functionally homologous genes is very similar in these two bacterial species. Furthermore, five additional fla genes were inferred to exist in E. coli in addition to the fla genes already identified. They were termed flaU, flaX, flaY, flaZ, and flbB (flb is equivalent to fla), which corresponded to flaFI, flaFVI, flaFVIII, flaFX, and flaK of Salmonella in this order. The flaK mutants of E. coli showed no complementation with any of the flaFV, flaFVI, flaFVII, flaFVIII, or flaFIX mutants of Salmonella.     

Living organisms from Prigogine’s perspective: an opportunity to introduce students to biological entropy balance

All living structures, from archaea to human, are open thermodynamic systems analysed through nonequilibrium thermodynamics. Nonequilibrium thermodynamics is a field with important applications to life sciences, which is very often left out of life science courses. A three-step method is suggested to make an easy introduction of nonequilibrium thermodynamics to life science students. The first step is to introduce the Prigogine equation dS = d_eS + d_iS, and explain the meaning of the entropy exchange with the surroundings d_eS and internal entropy generation in the system d_iS. The second step is to show that the Prigogine equation is connected to the equilibrium thermodynamics already known to students. This can be done by deriving the Clausius inequality dS ≥ dq/T, from the Prigogine equation applied to reversible and irreversible processes in closed systems. Reversible and irreversible processes are discussed separately and the results are then combined into the Clausius inequality. The third step is to introduce the fact that the Prigogine equation has a variety of applications in life sciences. This would give the students an opportunity to understand the entropy balance of physiological processes in cells and organisms. The import and accumulation of entropy, entropy generation, and entropy export could be made easier for students to adopt.     

Polarographic studies of the oxidation of vitamin K5 in aqueous solution.

Electrochemical behavior of 4-amino-2-methyl-1-naphthol hydrochloride (VK₅) has been studied by de and ac polarography in order to determine the applicability of these methods to the determination of VK₅ in aqueous solution. VK₅ exhibits two well-defined anodic waves on dc polarograms, one of which is due to the oxidation of VK₅ to the corresponding quinoimine and the other, to the formation of mercurous chloride on a dropping mercury electrode. Complete preremoval of dissolved oxygen makes the former wave reproducible, and its limiting current is found to be proportional to the VK₅ concentration ranging from 1.0 × 10^?5 to 1.0 × 10^?3m. On ac polarograms, electrooxidation of VK₅ also gives rise to a distinct peak whose height is proportional to the VK₅ concentration in the range of 5.0 × 10^?7 to 1.0 × 10^?5m. These facts can be applied to the microdetermination of VK₅ present in concentrations as low as the 0.1-ppm range.     

Inheritance and genetic mapping of resistance to Alternaria alternata f. sp. lycopersici in Lycopersicon pennellii

The fungal pathogen Alternaria alternata f. sp. lycopersici produces AAL-toxins that function as chemical determinants of the Alternaria stem canker disease in the tomato (Lycopersicon esculentum). In resistant cultivars, the disease is controlled by the Asc locus on chromosome 3. Our aim was to characterize novel sources of resistance to the fungus and of insensitivity to the host-selective AAL-toxins. To that end, the degree of sensitivity of wild tomato species to AAL-toxins was analyzed. Of all members of the genus Lycopersicon, only L. cheesmanii was revealed to be sensitive to AAL-toxins and susceptible to fungal infection. Besides moderately insensitive responses from some species, L. pennellii and L. peruvianum were shown to be highly insensitive to AAL-toxins as well as resistant to the pathogen. Genetic analyses showed that high insensitivity to AAL-toxins from L. pennellii is inherited in tomato as a single complete dominant locus. This is in contrast to the incomplete dominance of insensitivity to AAL-toxins of L. esculentum. Subsequent classical genetics, RFLP mapping and allelic testing indicated that high insensitivity to AAL-toxins from L. pennellii is conferred by a new allele of the Asc locus.     

Temperature preferences and tolerances of three fish species inhabiting hyperthermal ponds on mangrove islands

The fish species Cyprinidon artifrons, Floridichthys carpio, and Gambusia yucatana inhabit shallow mangrove ponds off the coast of Belize. Portions of these ponds experience a diurnal temperature change from 26 °C at night to 40 °C and above during midday. Repeated field observations indicate Cyprinidon prefer the warmer (and much larger) portions of the ponds whereas the other two species stay in the cooler areas.The hypothesis that temperature is serving as a cue for partitioning within the ponds was supported by laboratory thermal gradient tests in which Cyprinidon preferred temperatures clearly higher than the other two species.The critical thermal maximum (CTM) was determined for the three species using members that had been acclimated to either a daily cycling temperature similar to that for the ponds, or to the mean of the 24-hour cycle (30 °C). Cyprinidon acclimated to the cycling temperature had a CTM of 45.5 °C, which apparently sets a new record for fish CTM. Acclimation to a constant 30 °C lowered the CTM to 43.7 °C. Floridichthys and Gambusia acclimated to the cycled temperature had CTMs of 43.9 and 43.3 °C respectively, and 42.5 and 42.6 °C for those acclimated to 30 °C.All three species appear to have the ability to tolerate the high temperatures throughout the ponds but only Cyprinidon utilize the whole pond during the day. This may help to explain the large populations of Cyprinodon found in these mangrove ponds compared to the other species.     

Chromosomal localization of 13 candidate genes for human obesity in the pig genome

Thirteen candidate genes for human obesity were selected for cytogenetic mapping by FISH in the pig genome. Among them, 6 genes were assigned to chromosomes for the first time (NR3C1, GNB3, ADRB1, ADRB2, ADRB3 andUCP1). Location of the other 7 genes (INSIG2, LIPIN1, PLIN, NAMPT, ADIPOQ, UCP2 andUCP3), earlier mapped by somatic cell hybridization or with the use of a radiation hybrid panel, was verified (INSIG2) or more precisely described. The genes were assigned to the following chromosomes:INSIG2 to SSC15q12,LIPIN1 to SSC3q26,NR3C1 to SSC2q29,PLIN to SSC7q15,GNB3 to SSC5q21,NAMPT to SSC9q23,ADIPOQ to SSC13q41,ADRB1 to SSC14q28,ADRB2 to SSC2q29,ADRB3 to SSC15q13-14,UCP1 to SSC8q21-22, and bothUCP2 andUCP3 to SSC9p24. Most of the genes were located within known QTL for pig fatness traits.     

The effects of supplementing varying molecular weights of chitooligosaccharide on performance,selected microbial populations and nutrient digestibility in the weaned pig

An experiment (complete randomised design) was conducted to investigate the effects of supplementing different molecular weights (MW) of chitooligosaccharide (COS) on pig performance, selected microbial populations and nutrient digestibility post-weaning. A total of 396 weaned piglets (24 days of age, 7.3 kg ± (s.d.) 1.7 kg live weight) were assigned to one of six dietary treatments (22 replicates/treatment) for a 33-day experimental period. The dietary treatments were as follows (1) control diet (0 ppm COS), (2) control diet plus <1 kDa COS, (3) control diet plus 3 to 5 kDa COS, (4) control diet plus 5 to 10 kDa COS, (5) control diet plus 10 to 50 kDa COS and (6) control diet plus 50 to 100 kDa COS. The COS were included at 250 ppm in the diets. There was no significant effect of dietary treatment on piglet performance during the starter period (days 0 to 18; P > 0.05). However, there were quadratic responses in both daily gain (P < 0.05) and gain to feed ratio (P < 0.05) to the increased MW of COS inclusion during the weaner period (days 18 to 33) with all COS-supplemented treatments improving daily gain and gain to feed ratio compared with the control. There was a quadratic response in faecal scoring to the increased MW of COS inclusion from days 0 to 7 (P < 0.001), days 7 to 14 (P < 0.001) and during the overall experimental period (P < 0.01) with all the COS-supplemented treatments having an improved faecal score compared with the control. During the weaner period, there was a cubic response in lactic acid bacteria and Escherichia coli populations as the MW of COS increased (P < 0.05). The 5 to 10 kDa and 10 to 50 kDa COS increased lactic acid bacteria populations compared with the control, whereas lactic acid bacteria populations decreased at 50 to 100 kDa. The 5 to 10 kDa, 10 to 50 kDa and 50 to 100 kDa COS decreased E. coli populations compared with the control. There was a cubic response in the apparent total tract digestibility of dry matter (DM; P < 0.01), organic matter (OM; P < 0.01), ash (P < 0.01), nitrogen (N; P < 0.01) and gross energy (GE; P < 0.01) to the increased MW of COS inclusion during the weaner period. The 5 to 10 kDa COS had a higher apparent total tract digestibility of DM, OM, ash, N and GE in comparison to the control, whereas the apparent total tract nutrient digestibility of these nutrients decreased at 10 to 50 kDa. The current results indicate that the MW ranges of 5 to 10 kDa and 10 to 50 kDa COS decreased E. coli numbers while increasing nutrient digestibility of the diets.     

Mixture interactions of glutamate and betaine in single squid olfactory neurons

We used nystatin-patch techniques to characterize the responses of squid olfactory receptor neurons to the attractive odorant, L-glutamate, and to study mixture interactions between glutamate and the aversive odorant, betaine. We report that glutamate activates a cation-selective conductance that is permeable to Ca²⁺, K⁺, and Na⁺ and which would depolarize squid olfactory receptor neurons under physiological conditions. The responses to glutamate were concentration dependent. The EC₅₀ of individual cells ranged from 0.3 mmol · l⁻¹ to 85.0 mmol · l⁻¹. We found that individual cells were capable of responding to both glutamate and betaine, and that the relative magnitudes of these responses varied from cell to cell. Finally, we report that current responses to binary mixtures of glutamate and betaine are suppressed relative to the sum of the responses to the individual odors in single squid olfactory receptor neurons. Accepted: 20 October 1999     

THE EFFECT OF ENVIRONMENTAL VARIABLES ON THE OXYGEN CONSUMPTION OF THE PROTOBRANCH BIVALVE NUCULA TURGIDA (LECKENBY AND MARSHALL)

The oxygen consumption of the protobranch bivalve Nucula turgidawas measured in relation to size and to variation in temperatureand ambient oxygen tension. The slope of the line relating logsize and log oxygen uptake varied from 0.539 to 0.884 over therange 5°C to 40°C in summer – conditioned (S)animals but for winter – conditioned (W) animals the slopevaried from 0.561 to 0.762 over the range 5°C to 15°Conly; from 20°C to 35°C the values for the slope fellfrom 0.298 to 0.092. There was evidence of reverse acclimation,since the absolute rate of oxygen consumption was greater inS animals than in W over the temperature range studied. Thelethal limit for both groups appeared to be between 30°Cand 35°C. At all temperatures (5°C–25°C) N. turgida wasfound to be a near complete oxyconformer with b₂ x 10³ valuesranging from +0.0754 to –0.0234. The responses to temperature differ little from those of eulamellibranchbivalves, but the lack of ability to oxyregulate does demonstratea difference which may be linked to the different gill structure. (Received 13 January 1983;     

PARENT DEVELOPMENT

Today''s parents tend to be overwhelmed with advice from many sources. In his role as family counselor, the pediatrician must understand and consider the emotional development of parents in relation to their child''s development; otherwise, his advice and counsel do not “take” and he becomes tired and frustrated and angry.Parents progress through definite stages of development: Stage 1: Learning the cues—the struggle of the parents to interpret the infant''s needs. Stage 2: Learning to accept growth and development—the parent learning to accept some loss of control of the toddler. Stage 3: Learning to separate—the parent learning to allow the child to develop independently. Stage 4: Learning to accept rejection, without deserting—the struggle of the parents not to intrude and yet to be there when needed. Stage 5: Learning to build a new life having been thoroughly discredited by one''s teenager—the parent learning to live independently while the teenager struggles to develop his own identity.The pediatrician who is accepting, sensitive and a good listener and who keeps in mind that parents as well as children have capacities for growth and development, will be a potent factor in promoting good parent-child relationships and many times more effective in dealing with the child in health and disease.     

A simple statistical method for use in kinetic analysis based on Lineweaver-Burk plots

Statistical methods for the analysis of initial-velocity and/or inhibition data are described. They involve application of F tests (i) to determine goodness of fit to the first-order Michaelis-Menten equation, (ii) to predict the reaction mechanism by assessing slope and y-intercept effects in Lineweaver-Burk plots according to the inspection rules of Cleland [Cleland, W. W. (1963) Biochim. Biophys. Acta67, 188–196], (iii) to test the linearity of the replots of slopes or y-intercepts versus the reciprocal of the substrate concentration or the inhibitor concentration, and (iv) to estimate the true K_m or K_i values from these replots. The method serves to fill a gap in the kinetic analysis methodology between the antiquated graphical method and the sophisticated direct computer-fitting of data to a variety of possible rate equations. The entire theoretical and computational format is provided to allow the investigator to apply these statistical tests to his data using only a desk-top calculator.