Combining olfactory test and motion analysis sensors in Parkinson's disease preclinical diagnosis: a pilot study

OBJECTIVES

Preclinical diagnosis of Parkinson's disease (PD) is nowadays a topic of interest as the neuropathological process could begin years before the appearance of motor symptoms. Several symptoms, among them hyposmia, could precede motor features in PD. In the preclinical phase of PD, a subclinical reduction in motor skills is highly likely. In this pilot study, we investigate a step-by-step method to achieve preclinical PD diagnosis.

MATERIAL AND METHODS

We used the IOIT (Italian Olfactory Identification Test) to screen a population of healthy subjects. We identified 20 subjects with idiopathic hyposmia. Hyposmic subjects underwent an evaluation of motor skills, at baseline and after 1 year, using motion analysis sensors previously created by us.

RESULTS

One subject showed significant worsening in motor measurements. In this subject, we further conducted a dopaminergic challenge test monitored with the same sensors and, finally, he underwent [¹²³ I]-FP/CIT (DaTscan) SPECT brain imaging. The results show that he is probably affected by preclinical PD.

CONCLUSIONS

Our pilot study suggests that the combined use of an olfactory test and motor sensors for motion analysis could be useful for a screening of healthy subjects to identify those at a high risk of developing PD.

Louis Appia (1818-98): military surgeon and member of the International Committee of the Red Cross

From Appia's writings we compose a view on his contribution to international medical relief in warfare, to the establishment of the Red Cross and the Geneva Convention, and to surgical procedures on the battlefield. Much information comes from his work on the Battle of San Martino e Solferino in June 1859 on the subject of which he wrote seven letters. We report also on his role during the Garibaldinian Campaign in 1866 and his work in Europe as a member of the International Committee of the Red Cross (ICRC).

[The pacifism of Henry Dunant]

From various writings of the founder of the International Red Cross and above all from his late work L'avenir sanglant it is deduced as the Dunant anticipating and prophetically interpreting the curse of the war is an internationalist (for some aspects a romantic anarchist) and a convinced pacifist. We show therefore how much has been false and backbiters the defamations that followed to the attribution of the first Nobel prize for the peace.

Rewriting of the biography of Henry Dunant, the founder of the International Red Cross

This paper presents quite a different version of the origins of the Red Cross from that officially recognised. On the basis of historical documents and statements of authors who are critical and attentive to the detail of the circumstances and events which gave rise to the Red Cross, it is possible to discern a surprising historical truth.

Lifestyle-related risk factors for Parkinson's disease: a population-based study

OBJECTIVES

To investigate the association of major lifestyle-related risk factors with the prevalent cases of Parkinson's disease (PD) identified by the Italian Longitudinal Study on Aging.

METHODS

A total of 5632 individuals randomly selected from the population registers of eight centers were screened for parkinsonism using both a questionnaire and a neurologic examination. Screened positives underwent a structured clinical work-up for the diagnosis of parkinsonism and parkinsonism subtypes.

RESULTS

We identified 113 prevalent cases of PD. Age, male gender, and pesticide-use license were significantly related to PD. Heavy smoking was inversely related to PD. Age (OR = 1.1; 95% CI, 1.06-1.15) and pesticide-use license (OR = 3.7; 95% CI, 1.6-8.6) kept their significant correlation with the disease in the multivariate analysis to adjust for all the variables under investigation. Multivariate analyses were made for men and women separately: pesticide exposure was positively associated with PD only in men.

CONCLUSIONS

Pesticide exposure might represent a candidate for environmental factors involved in PD.

Lipoprotein(a) and cognitive performances in an elderly white population: Cross-sectional and follow-up data

BACKGROUND AND PURPOSE

Elevated lipoprotein(a) [Lp(a)] serum levels have been associated with an increased risk of vascular diseases, and preliminary observations suggest that they are a risk factor for vascular dementia. The relationship between Lp(a) levels and cognitive performances in the general population has never been investigated. Our aim was to evaluate the effect of elevated Lp(a) levels on cognitive functions in the elderly.

METHODS

Cognitive performances were assessed by means of the Mini-Mental State Examination (MMSE), the Babcock Short Story, and the Matrix Test in a population sample of 435 white subjects aged 65 to 84 years who were evaluated at baseline and after 3 years. Lp(a) levels were determined by ELISA.

RESULTS

No statistically significant difference was found in neuropsychological test scores between subjects with and without elevated Lp(a) levels, although subjects with elevated Lp(a) levels had slightly better cognitive performances. This difference reached a statistical significance level only in a subscore of the Matrix Test (number of correct responses) when adjusted for age, sex, education, smoking, and history of stroke. At follow-up, no statistically significant difference was found in cognitive performances between subjects with and without elevated Lp(a) serum levels in either univariate or multivariate analyses. Subjects with and without elevated Lp(a) showed a similar decline rate during follow-up.

CONCLUSIONS

In this sample of elderly white subjects, elevated Lp(a) levels were not associated with poorer cognitive performances or with an increased rate of cognitive decline. Elevated Lp(a) levels do not appear to be a major determinant of cognitive impairment in the elderly.

Lipoprotein(a) serum levels and vascular diseases in an older Caucasian population cohort. Italian Longitudinal Study on Aging (ILSA)

OBJECTIVE

To investigate elevated lipoprotein(a) [Lp(a)] levels as a risk factor for stroke, myocardial infarction, angina, intermittent claudication, and combination of the above in a cohort of unselected older individuals.

DESIGN

Population cohort from one of the eight centers participating in the Italian Longitudinal Study on Aging (ILSA).

SETTING

General community.

PARTICIPANTS

A subsample of 446 subjects (M/F: 231/ 215, mean age: 74.5 +/- 5.7 years) of the original, randomly selected, population cohort of 704 individuals, 65 to 84 years of age, free-living or institutionalized in the Impruneta Municipality, area of Florence, Italy.

MEASUREMENTS

Conventional vascular risk factors and vascular diseases defined following a two-step procedure (screening phase and confirmation on positives) using standard and validated criteria. Lp(a) levels determined by an ELISA method.

RESULTS

No association was observed between elevated Lp(a) levels alone and any of the examined vascular diseases (stroke, myocardial infarction, angina, and intermittent claudication). In contrast, examining the interactions between elevated Lp(a) and conventional vascular risk factors, when elevated Lp(a) was combined with a history of smoking, a marked increase in the risk of vascular diseases combined (odds ratio [OR]: 4.12; 95% confidence interval [CI]: 1.27-13.40) was observed, much higher than that expected based on the additive effect of smoking and elevated Lp(a) alone.

CONCLUSIONS

With the cautions due to the cross-sectional design of the study and the limited statistical power, these results suggest a possible synergistic effect between elevated Lp(a) levels and other pro-atherogenic factors such as smoking on the risk of vascular diseases in older individuals.

Characteristics, outcome, and care of stroke associated with atrial fibrillation in Europe: data from a multicenter multinational hospital-based registry (The European Community Stroke Project)

BACKGROUND AND PURPOSE

The role of atrial fibrillation (AF) as a determinant of stroke outcome is not well established. Studies focusing on this topic relied on relatively small samples of patients, scarcely representative of the older age groups. We aimed at evaluating clinical characteristics, care, and outcome of stroke associated with AF in a large European sample.

METHODS

In a European Concerted Action involving 7 countries, 4462 patients hospitalized for first-in-a-lifetime stroke were evaluated for demographics, risk factors, clinical presentation, resource use, and 3-month survival, disability (Barthel Index), and handicap (Rankin scale).

RESULTS

AF was present in 803 patients (18.0%). AF patients, compared with those without AF, were older, were more frequently female, and more often had experienced a previous myocardial infarction; they were less often diabetics, alcohol consumers, and smokers (all P:<0.001). At 3 months, 32.8% of the AF patients were dead compared with 19.9% of the non-AF patients (P:<0.001). With control for baseline variables, AF increased by almost 50% the probability of remaining disabled (multivariate odds ratio 1.43, 95% CI 1.13 to 1.80) or handicapped (multivariate odds ratio 1.51, 95% CI 1.13 to 2.02). Before stroke, only 8.4% of AF patients were on anticoagulants. The chance of being anticoagulated was reduced by 4% per year of increasing age. AF patients underwent CT scan and other diagnostic procedures less frequently and received less physiotherapy or occupational therapy.

CONCLUSIONS

Stroke associated with AF has a poor prognosis in terms of death and function. Prevention and care of stroke with AF is a major challenge for European health systems.

Parkinson's disease and parkinsonism in a longitudinal study: two-fold higher incidence in men. ILSA Working Group. Italian Longitudinal Study on Aging

OBJECTIVE

To determine the incidence of parkinsonism and PD in the Italian elderly, and to explore the relation with age and gender.

METHODS

In eight Italian municipalities, a population-based, parkinsonism-free cohort was followed for an average of 3 years. At the end of the follow-up, the cohort survivors were directly contacted (screening and clinical examination). Cohort members who had died were studied using death certificates, clinical records, and information gathered from relatives and general practitioners. Parkinsonism diagnosis and subtyping were made according to specified diagnostic criteria.

RESULTS

The cohort consisted of 4,341 individuals (65 to 84 years of age): 596 died before the examination, 2,863 (76.4% of the survivors) completed the screening procedure, and 882 refused to participate. The authors found 68 incident cases of parkinsonism: 42 PD (62%), 7 drug-induced parkinsonism (10%), 8 parkinsonism in dementia (12%), 8 vascular parkinsonism (12%), and 3 parkinsonism, unspecified (5.8%). Average annual incidence rate (per 100,000 person-years) in the population aged 65 to 84 years, adjusted to the 1992 Italian population, was 529.7 (95% CI, 400.5 to 658.9) for parkinsonism, and 326.3 (95% CI, 224.1 to 427.5) for PD. Incidence rates for both parkinsonism and PD increased with age in both men and women; men had higher rates in every age group. Age-adjusted relative risk in men compared with women was 1.66 (95% CI, 1.02 to 2.70) for parkinsonism and 2.13 (95% CI, 1.11 to 4.11) for PD.

CONCLUSIONS

Incidence of parkinsonism and PD increased with age, PD was the most common type of parkinsonism, and men had a risk of developing PD twice that of women.

Multisite inhibition of Pinus pinea isocitrate lyase by phosphate

Our results show that the phosphate ion is a nonlinear competitive inhibitor of Pinus pinea isocitrate lyase. In addition, this compound induces a sigmoidal response of the enzyme, which usually exhibits standard Michaelis-Menten kinetics. This peculiar behavior of P. pinea isocitrate lyase could be explained by a dimer (two-site) model, in which phosphate binds cooperatively, but the affinity of the vacant site for substrate (the magnesium-isocitrate complex) remains the same. As a result, the interaction of phosphate with free enzyme produces an inhibitor-enzyme-inhibitor species that is of significant importance in determining reaction rate; a possible regulatory role of the glyoxylate cycle by inorganic phosphate is suggested. The mode of phosphate inhibition is consistent with both the mechanism for magnesium ion activation of P. pinea isocitrate lyase and its site heterogeneity. Our results explain the cooperative effects observed by some authors in kinetic studies of isocitrate lyase carried out in phosphate buffers and also account for the higher K(m) values determined by using such assay systems. Phosphate buffer should be avoided in performing isocitrate lyase kinetics.

Stroke in the very old : clinical presentation and determinants of 3-month functional outcome: A European perspective. European BIOMED Study of Stroke Care Group

BACKGROUND AND PURPOSE

The oldest old represent the fastest-growing segment of the elderly population in developed countries. Knowledge of age-specific aspects of stroke is essential to establish diagnostic and therapeutic pathways and to set up prevention and rehabilitation programs. We sought to evaluate stroke features and functional outcome in patients aged >/=80 years compared with the younger age groups.

METHODS

In a European Union Concerted Action involving 7 countries, 4499 patients hospitalized for first-in-a-lifetime stroke were evaluated for demographics, risk factors, clinical presentation, resource use, and 3-month disability (Barthel Index) and handicap (Rankin Scale).

RESULTS

Overall, 3141 patients (69.8%) were aged <80 years, and 1358 (30.2%) were aged >/=80 years. At baseline, female sex, prestroke institutionalization, and a worse prestroke Rankin score were significantly more frequent in the older patients, as were coma, paralysis, swallowing problems, and urinary incontinence in the acute phase (all P values <0.001). Brain imaging and other diagnostic tools were significantly less used in the older patients. Paralysis, swallowing problems, and incontinence during hospitalization independently predicted 3-month disability or handicap in both groups. For the older patients, prestroke institutionalization proved a further strong and independent determinant of 3-month disability (odds ratio, 2.33; 95% CI, 1.22 to 4.45) and handicap (odds ratio, 7.04; 95% CI, 1.62 to 30. 69).

CONCLUSIONS

In the very old, both medical and sociodemographic factors may significantly influence stroke outcome, showing peculiar characteristics. Knowledge of these determinants may reduce the burden on health systems, improving quality of care.

Joseph Daquin, Piedmontese Savoyard physician, a "not well-known chiarugi"

We present a critical review of La philosophie de la folie, second edition, published in 1804. Joseph Daquin's thoughts and clinical activity in the psychiatric field are described. Daquin's ideas about various forms of madness and the different therapeutic, moral, physical treatments, his anatomical studies, successes and failures are presented. Several clinical cases are described. The author's view of the moon's influence on madness is described. Finally it is shown how very important was the human person and the moral treatment of madness for Daquin, in contrast with the current opinion at the end of 1700.

Enzyme kinetic parameters are not altered by microgravity

This paper deals with a microgravity experiment concerning the EMEC project (Effect of Microgravity on Enzymatic Catalysis), performed during the parabolic flight of the sounding rocket MASER 7, launched from the base of Esrange (Kiruna, Sweden) on May 3, 1996. The experiment consisted of performing, in a microgravity environment, a number of velocity measurements of an enzyme (isocitrate lyase) catalyzed reaction at different substrate concentrations, to calculate the kinetic parameters (Km and Vmax), which were compared with those obtained at standard gravity, with identical instrumentation. The experimental hardware, the EMEC module, expressly set up by Officine Galileo (Firenze, Italy) with the financial support of the European Space Agency, was a multichannel fibre-optics radiometer, equipped with an automatic injection system, that allowed to measure simultaneously the transmittance changes in 16 reaction cells. The results indicated that under the experimental conditions applied, microgravity has no appreciable effect on the enzyme kinetic constants.

Incidence and determinants of poststroke dementia as defined by an informant interview method in a hospital-based stroke registry

BACKGROUND AND PURPOSE

Inconsistent information about incidence and determinants of poststroke dementia might be related to patient attrition, partly because of nonapplicability of formal neuropsychological testing to a large proportion of patients registered in a definite setting.

METHODS

Using a proxy-informant interview based on ICD-10 criteria, we determined dementia at stroke onset and 1 year after stroke in the 339 patients who survived, were available for follow-up, and were not demented at stroke onset of 635 patients entered over a 1-year period in a stroke registry taken at 2 community hospitals in Florence, Italy.

RESULTS

Of the 339 patients, 57 (16.8%) proved to have poststroke dementia. These patients were older, more frequently female, and more often (multivariate odds ratio, 2.35; 95% CI, 1.21 to 4.58) had atrial fibrillation than those without dementia. Aphasia and the clinical features expressing the severity of the stroke event in the acute phase predicted poststroke dementia.

CONCLUSIONS

In a hospital-based nonselected series of stroke survivors, despite the use of a method with low sensitivity for defining dementia, our study confirms that dementia is a frequent sequela of stroke and is mainly predicted by stroke severity. Certain determinants could be controlled in the prestroke phase, thus reducing its risk.

Gravitational effects on biological systems

The possible effects of the earth's gravitational field on biological systems have been studied from a quantitative point of view, focusing the attention to a very simple system, a solution containing proteins, which biochemists might use in experiments. Gravity has been compared with other forces which are known to influence protein activity, including thermic agitation, weak electrostatic interactions, Van der Waals forces and viscous dissipation. Comparisons have been described in terms of the energy of the interaction per mole, referring to some physically simple cases and substances of biological interest. From this study it is evident that the earth's gravitational energy should be taken into account when considering the chemical behaviour of solutions containing substances that have high molecular weight, such as a typical protein, since its value is comparable to other weak interactions. Moreover, since solutions represent the basis of much more complex biological processes taking place inside cells, the influence of gravity should extend also to cellular biochemical behaviour, especially in presence of altered gravity, both in microgravity (such as on satellites orbiting around the earth), and in macrogravity (such as in a centrifugating biological system).

[Luigi Guerri, an ordinary pharmacists who became the "first son" of pharmaceutical chemistry]

Luigi Guerri (1823-1892) was one of the most important researchers and teachers in pharmaceutic chemistry in Florence in XIX century. Born and lived in Florence, patriot and colleague of the famous Ugo Schiff, from whom he received much praise, Guerri taught and carried out research into chemistry for about forty years at "Istituto di Studi Superiori" in Florence. This article is a synthesis of his career which started as first assistant to professor Campani, then he became a full professor, teaching pharmaceutic chemistry and eventually became the director of the pharmaceutic laboratory in "Arcispedale Santa Maria Nuova". This article, with the reproduction of some of Guerri's publications, shows the integrity of the man as a chemist and as a teacher. He was commemorated by Schiff and the scientific journal "Orosi" at his death.

A continuous spectrophotometric assay for alkaline phosphatase with glycerophosphate as substrate

We describe a continuous coupled spectrophotometric assay for alkaline phosphatase which uses alpha- or beta-glycerophosphate as substrate, and glycerol dehydrogenase as ancillary enzyme. The glycerol liberated by alkaline phosphatase is determined by measuring the increase in absorbance at 340 nm caused by NADH formation that is combined with glycerol oxidation by the ancillary enzyme. The assay procedure was optimized using a bovine bone extract as alkaline phosphatase source.

Is the salivary "ferning" a reliable index of the fertile period?

We found that the fern leaf crystallisation of human saliva is a non-specific phenomenon, independent on the action of estrogenic hormones. Salivary ferning can be obtained in practice during the whole menstrual cycle and occurs in the saliva of postclimateric, pregnant and prepuberal women. Even the saliva of male subjects gives invariably the ferning reaction. In conclusion, salivary ferning does not seem a reliable method to establish woman fertile period.

A new continuous optical assay for maltase and sucrase

A new method for the assay of maltase and sucrase is reported. The method makes use of mutarotase, hexokinase and glucose 6-phosphate dehydrogenase as ancillary enzymes. The reaction is linear at least up to a delta E/min of 0.13.

Substrate-decreased modification by diethyl pyrocarbonate of two histidines in isocitrate lyase from Escherichia coli

The inactivation of tetrameric 188-kDa isocitrate lyase from Escherichia coli at pH 6.8 (37 degrees C) by diethyl pyrocarbonate, exhibiting saturation kinetics, is accompanied by modification of histidine residues 266 and 306. Substrates isocitrate, glyoxylate, or glyoxylate plus succinate protect the enzyme from inactivation, but succinate alone does not. Removal of the carbethoxy groups from inactivated enzyme by treatment with hydroxylamine restores activity of isocitrate lyase. The present results suggest that the group-specific modifying reagent diethyl pyrocarbonate may be generally useful in determining the position of active site histidine residues in enzymes.

Effect of Mg2+ and Mn2+ on isocitrate lyase, a non-essentially metal-ion-activated enzyme. A graphical approach for the discrimination of the model for activation

We describe a simple method for the analysis of activation systems in which a metal ion modifier may combine with either the enzyme or the substrate (or both) and the metal ion-substrate complex is the true substrate of the enzyme reaction. The suggested approach is essentially a 'graphical' method that both provides unbiased criteria for the choice of the activation mechanism and yields good rough estimates of the kinetic parameters. The procedure, tested on a variety of simulated models, produces appropriate and reliable results. Applying this treatment to isocitrate lyase, we confirmed the data previously reported for Mg2+ [Giachetti, Pinzauti, Bonaccorsi & Vanni (1988) Eur. J. Biochem. 172, 85-92], and we found that Mn2+ functions with the same mechanism as does Mg2+, but with quite different kinetic constants. In particular, its ratio of the Vmax, values of the activated and the non-activated enzyme is less than 1, and thus Mn2+ is to be considered an inhibitor rather than an activator.

The interaction of 3-phosphoglycerate and other substrate analogs with the glyoxylate- and succinate-binding sites of isocitrate lyase

The gene for isocitrate lyase from Escherichia coli has recently been cloned and sequenced. However, knowledge of this enzyme from E. coli is limited. Because of the possible role of 3-phosphoglycerate as a metabolic inhibitor of isocitrate lyase in E. coli, a detailed analysis of this compound as an inhibitor is reported in this paper. Kinetic data suggest that 3-phosphoglycerate is an analog of isocitrate (or glyoxylate) and also that it competes with succinate, or succinate analogs, by interfering with their binding to the enzyme. This could be due to the steric bulk of the phosphate moiety of 3-phosphoglycerate extending in the direction of and over the succinate-binding site. The interaction of other substrate analogs, including glycolate, oxalate, phosphoenolpyruvate, and cis-aconitate, with isocitrate lyase from E. coli is also characterized.

Enzymes of human cervical mucus: a comparative study on fertile and infertile mucus and on the endocervical epithelium

We report a comparative study on protein and enzyme content of human periovulatory cervical mucus and endocervical epithelium. The salient results of our investigation are summarized in the following three points: 1) The method of taking of cervical mucus samples may markedly affect the results of protein and enzyme assays. It is warmly advisable to collect mucus samples from the endocervical canal. 2) Cervical mucus from women diagnosed as having cervical-factor infertility is oligoproteic and lacks some enzyme activities always present in normal cases. 3) Human cervical mucus and endocervical epithelium are very similar as for the enzyme distribution, but show quite different LDH-isoenzyme patterns. In the latter tissue, the H subunits constitute about 77 per cent of the whole LDH, suggesting that this enzyme here is functioning to produce pyruvate rather than lactate.

Glucose transport during ageing by human intestinal brush-border membrane vesicles

Glucose absorption by the small intestine is a complex phenomenon, that can be successfully studied by means of isolated brush-border and basolateral membrane vesicles of the enterocytes. We have carried out transport experiments on isolated brush-border membrane vesicles from the human small intestine, taking into account the age of the subjects. Our studies demonstrated that Na+-glucose cotransporter activity decreased as age increased with the "overshoot" phenomenon disappearing altogether in the oldest subjects. This effect was compared to that observed in intestinal membrane vesicles of young patients suffering from Crohn's disease; in this case there was a marked decrease in the Na+-dependent D-glucose uptake, but the "overshoot", even though low, was present. K+-dependent D-glucose transport, diffusion of L-glucose and the levels of some enzyme markers for intestinal brush-border membranes were also studied.

A continuous spectrophotometric assay for the enzymatic marker glucose 6-phosphatase

A continuous spectrophotometric assay for glucose 6-phosphatase is described. The method uses glucose dehydrogenase and mutarotase as ancillary enzymes. Glucose 6-phosphatase activity is measured by following NADH formation at 340 nm. The method is linear, at least up to 38 mU in the test which corresponds to a delta E of 0.24 min-1, when the enzyme is assayed in a microsomal fraction. We also discuss the method's suitability for subcellular fractionation. No other continuous assay for this important enzymatic marker of the endoplasmic reticulum is currently available.

Neutral maltase of human granulocytes: localization on the extracytoplasmic side of the plasma membrane and some properties

Neutral maltase is an alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) which is present in human granulocytes and B-lymphocytes but not in T-lymphocytes. These cells have been reported to contain a renal-type neutral maltase which cross-reacts with an antiserum raised against kidney brush-border enzyme. No study has been performed to assess the subcellular localization of the enzyme. Molecular properties of leukocyte neutral maltase from any species are unknown. We report in this paper that neutral maltase is present on the extracytoplasmic side of human granulocyte plasma membrane. These results are supported by subcellular fractionation on Percoll gradient and by papain digestion of intact granulocytes. The enzyme is probably an integral membrane protein. The anchorage to the lipid bilayer may be similar to that of the stalked brush-border hydrolases. Some properties of granulocyte neutral maltase were also determined on a plasma membrane-enriched fraction. The enzyme cleaves maltose and nigerose but not other glucosides disaccharides and oligosaccharides. The Km for maltose is (+/- SD) 0.78 (+/- 0.06) mM, that for nigerose 21.05 (+/- 1.43) mM. The Vmax for nigerose is 0.83-fold that for maltose. Tris, maltotriose, maltotetraose, and maltopentaose were inhibitors of granulocyte neutral maltase.

Isocitrate lyase from Pinus pinea. Characterization of its true substrate and the action of magnesium ions

We found that the Mg-isocitrate complex is the true substrate for pine isocitrate lyase and that magnesium acts as a non-essential activator. Both the non-activated and the activated enzyme forms are catalytically active. Our model is consistent with the presence of two Mg-binding sites with different affinities: an activator site with high affinity in addition to the catalytic site with lower affinity. This may result in a complex, fine regulation of isocitrate lyase activity by magnesium. The affinity of the free enzyme for isocitrate is very low. Moreover, free isocitrate does not bind to the activated enzyme, nor it can yield a catalytically active form by binding to an enzyme species whose catalytic site has already been bound by magnesium.

1-O-n-octyl-beta-D-glucopyranoside as a competitive inhibitor of Na+-dependent D-glucose cotransporter in the small intestine brush-border membrane

1-O-n-Octyl-beta-D-glucopyranoside is a competitive inhibitor of the Na+-dependent D-glucose uptake into rabbit, rat and human intestinal brush-border membrane vesicles. The lack of effect on the equilibrium uptake demonstrates that the detergent does not act by rupturing the vesicles; no membrane leakiness was apparent at the concentrations of octylglucopyranoside used, since D-glucose uptake is not inhibited even in the absence of the Na+ gradient (in K+ solution). There is a competitive interaction between octylglucopyranoside and D-glucose, as shown by Dixon and by Hunter and Down plots. The selectivity of the detergent effect is confirmed by its modest influence on amino acid uptake.

D-glucose uptake in intestinal brush-border membrane vesicles of rachitic rats

We have previously reported the metabolic consequences of feeding rats Steenbock and Black's rickets-inducing diet, deficient in vitamin D and with an altered Ca/P ratio. Using isolated brush-border membrane vesicles prepared from the jejunum, ileum and duodenum of control and rachitic rats, we have demonstrated a marked decrease of Na+-dependent D-glucose uptake at jejunum-ileum level of rachitic rats. At duodenum level Na+-dependent D-glucose transport was not influenced by rickets. A lack of any significant difference between the two animal groups was observed studying the facilitated transport of D-glucose, the diffusion of L-glucose and the Na+-dependent uptake of phenylalanine and aspartate.

Activities of NAD-and NADP-specific isocitrate dehydrogenases in kidney mitochondria of rachitic rat

In the previous research we have demonstrated that rats fed on a rickets-inducing diet show increasing citrate levels in kidney and intestinal mucosa. The study of the enzymes related to citrate metabolism has shown that both NAD+-and NADP+-dependent isocitrate dehydrogenases decrease in kidney mitochondria of rachitic rat. The inhibitory effect of Ca2+ and citrate on the activity of the two dehydrogenases has been also investigated; these metabolites behave as competitive inhibitors against Mg2+ both in normal and in rachitic rats.

Changes in enzyme levels in human cervical mucus during the menstrual cycle

Cervical mucus is a complex secretion produced by the endocervical epithelium. A comparative analysis of 30 enzymes was carried out on 15 women during their periovulatory period (days 10 to 16 of the menstrual cycle). Nine different enzymes were always found to be present in the cervical mucus. Changes in enzymatic activity were further studied in two of the women, one with a normal (27-day) and the other with a short (20-day) menstrual cycle. The data were compared with those for the same enzymes in the saliva of these two women. Each woman's ovulation time was determined through hormone measurements in urine and blood, as well as by recording basal body temperature and by Billing's method. Our results indicate that a maximum peak occurs for several enzymes during the periovulatory period.

Steady-state kinetic analysis of isocitrate lyase from Lupinus seeds: considerations on a possible catalytic mechanism of isocitrate lyase from plants

Isocitrate lyase catalyzes the reversible cleavage of isocitrate into glyoxylate and succinate. The kinetic mechanism of bacterial isocitrate lyase has been reported to be ordered uni-bi. Moreover, it has been proposed that isocitrate lyase in higher plants may be switched on and off by a succinylation/desuccinylation mechanism. Similarly to bacterial citrate lyase, in which an acetylation/deacetylation mechanism is operative, succinylation might also play a role in the catalytic mechanism of plant isocitrate lyase. We have investigated the kinetic mechanism of isocitrate lyase from Lupinus seeds. The results reported in this paper show that the system follows a preferentially ordered uni-bi pathway in which the succinate is released first. On the basis of our results and some other recently reported data, we conclude that it is unlikely that bacterial and plant isocitrate lyases have different catalytic mechanisms.

An isocitrate lyase of higher plants: analysis and comparison of some molecular properties

A new purification procedure for isocitrate lyase from Pinus pinea is reported. The final preparation shows charge homogeneity and a purity degree higher than 95%. It is possible to remove catalase completely by exploiting the high hydrophobicity of isocitrate lyase. The enzyme has a Mr of 264,000 and is likely composed of four subunits, each with a Mr of 66,000. The binding of radioactively labeled oxalate revealed four catalytic sites per oligomer. These data suggest that isocitrate lyase subunits are similar, if not identical. The Michaelis constant for isocitrate is equal to 33 microM; molecular activity is about 2670 mol X min-1 X mol of enzyme-1. The amino acid composition of the enzyme was also determined. Isocitrate lyase appears resistant to proteolysis by carboxypeptidase A. Hydrazinolysis, Edman degradation, and dansyl chloride treatment indicate that both carboxy and amino terminals are probably inaccessible or blocked.

Inactivation and degradation of yeast glucose-6-phosphate dehydrogenase selectively modified by pyridoxal-5-phosphate

Modification by pyridoxal-5-phosphate of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) purified from Saccharomyces cerevisiae produces an inactivation effect, partially reversible by dilution in the presence of substrates. Spectroscopic analysis of the enzyme pyridoxal-5-phosphate complex reduced with NaBH4 provides the values expected for the binding of the aldehydic group to Lys residue. One Lys residue appears to be responsible for the observed enzyme inactivation, and the presence of the phosphate group is required for the effect. Besides the change of activity, the binding of pyridoxal-5-phosphate to the enzyme causes an increase in susceptibility to degradation by the intracellular yeast proteinase A at pH 7.6.

Some molecular features of human cervical mucus

1) The time preservation effect of the enzymatic activities present in human cervical mucus has been studied. 2) In order to protect the enzymatic activities of the mucus from bacterial impurities, the enzymes studied were assayed in presence of NaN3. 3) The effect of an acid pH likes present in the vagina was also studied: a low pH exerts a marked inhibition on mucus enzymes. 4) the use of nonionic detergents for mucus solubilization does not produce a marked increase of the enzymatic activities studied. 5) A NADP-dependent malate dehydrogenase in peri- and post-ovulatory period has been identified. 6) The presence in mucus of at least four lactate dehydrogenase isoenzymes has been demonstrated and their absolute values determined.