Ornithine decarboxylase from Leishmania mexicana promastigotes: interaction with pyridoxal 5'-phosphate and alpha-difluoromethylornithine

The catalytic properties of ornithine decarboxylase (ODC) from Leishmania mexicana as well as the interaction with its cofactor pyridoxal 5'-phosphate (PLP) and the irreversible inhibitor alpha-difluoromethylornithine (DFMO) have been studied using partially purified preparations of the enzyme obtained from parasite promastigotes. Leishmania extracts prepared in the presence of saturating concentrations of PLP yielded an enzyme considerably more resistant to heat inactivation and with a three-fold higher activity than the ODC obtained without the addition of cofactor. The complete removal of PLP by treatment with hydroxylamine yielded the apoenzyme which shows an absolute requirement for PLP to recover its enzymatic activity. The Km values for L-ornithine and PLP were 0.7 mM and 25 microM, respectively, while Ki for DFMO was 0.2 mM. The restoration of ODC activity from apoenzyme and cofactor seems to involve time and temperature-dependent activation processes. L. mexicana ODC has an apparent molecular mass of 240 +/- 20 kDa.     

The impact of unemployment on health: a review of the evidence

OBJECTIVE: To review the scientific evidence supporting an association between unemployment and adverse health outcomes and to assess the evidence on the basis of the epidemiologic criteria for causation. DATA SOURCES: MEDLINE was searched for all relevant articles with the use of the MeSH terms "unemployment," "employment," "job loss," "economy" and a range of mortality and morbidity outcomes. A secondary search was conducted for references from the primary search articles, review articles or published commentaries. Data and definitions of unemployment were drawn from Statistics Canada publications. STUDY SELECTION: Selection focused on articles published in the 1980s and 1990s. English-language reports of aggregate-level research (involving an entire population), such as time-series analyses, and studies of individual subjects, such as cross-sectional, case-control or cohort studies, were reviewed. In total, the authors reviewed 46 articles that described original studies. DATA EXTRACTION: Information was sought on the association (if any) between unemployment and health outcomes such as mortality rates, specific causes of death, incidence of physical and mental disorders and the use of health care services. Information was extracted on the nature of the association (positive or negative), measures of association (relative risk, odds ratio or standardized mortality ratio), and the direction of causation (whether unemployment caused ill health or vice versa). DATA SYNTHESIS: Most aggregate-level studies reported a positive association between national unemployment rates and rates of overall mortality and mortality due to cardiovascular disease and suicide. However, the relation between unemployment rates and motor-vehicle fatality rates may be inverse. Large, census-based cohort studies showed higher rates of overall mortality, death due to cardiovascular disease and suicide among unemployed men and women than among either employed people or the general population. Workers laid off because of factory closure have reported more symptoms and illnesses than employed people; some of these reports have been validated objectively. Unemployed people may be more likely than employed people to visit physicians, take medications or be admitted to general hospitals. A possible association between unemployment and rates of admission to psychiatric hospitals is complicated by other institutional and environmental factors. CONCLUSIONS: Evaluated on an epidemiologic basis, the evidence suggests a strong, positive association between unemployment and many adverse health outcomes. Whether unemployment causes these adverse outcomes is less straightforward, however, because there are likely many mediating and confounding factors, which may be social, economic or clinical. Many authors have suggested mechanisms of causation, but further research is needed to test these hypotheses.     

The target switch algorithm: a constructive learning procedure for feed-forward neural networks

We propose an efficient procedure for constructing and training a feed-forward neural network. The network can perform binary classification for binary or analogue input data. We show that the procedure can also be used to construct feedforward neural networks with binary-valued weights. Neural networks with binary-valued weights are potentially straightforward to implement using microelectronic or optical devices and they can also exhibit good generalization.     

Myoclonus associated with hyperthyroidism and thymoma: a case report

Movement disorders associated with hyperthyroidism or thymoma are extremely rare. A 52-year-old woman had developed myoclonus since June, 1989. Hyperthyroidism and thymoma were diagnosed 1 month and 9 months later. Myoclonus improved after thyroid treatment and thymectomy. If the association was not only a coincident phenomenon, autoimmunity should be considered in this previously unrecognized association.     

Cricopharyngeal myotomy in amyotrophic lateral sclerosis

Reported herein is the experience of the authors with 38 amyotrophic lateral sclerosis (ALS) patients for whom cricopharyngeal myotomy was performed. The major surgical objectives were facilitation of swallowing and amelioration of the tendency of these patients to aspirate ingestants and secretions. In the group of these patients in which the follow-up information has been adequate, 64% were improved and 36% experienced no significant benefits. The authors' surgical indications, methods of anesthesia, surgical technique, and postoperative care are described.     

POLLUTER PAYS THROUGH LOAD-BASED LICENSING: THE IMPACT FOR A COASTAL SEWAGE-TREATMENT WORKS

Implementation of the 'polluter pays'principle through load-based licensing encourages the prevention and reduction of pollution through the financial incentive of lower pollutant fees. It encourages fairness and equity in environmental-protection licence fees among industries, based upon their individual environmental performance in reducing and managing pollution and risks and endeavours, to shift (internalise) external pollution costs from society to the polluter. It takes account of (a) pollutant load, (b) toxicity and (c) sensitivity of the receiving environment to which pollutants are released. This study shows that a coastal sewage-treatment works of 34 Ml/d average capacity will be better off every subsequent year with the implementation of load-based licensing - at least for the period 2000–2005.     

Selective distribution of the heparin in mammals: conspicuous presence of heparin in lymphoid tissues

The systematic study on the distribution of heparin in 12 tissues of eight mammalian species is reported. It is shown that heparin varies from 1 microgram/g of dry tissue in cat liver up to 1000 micrograms/g of dry tissue in bovine ileum. Heparin was present in relatively high amounts in lung, ileum and skin, of most of the species analysed. It was also observed that heparin was conspicuously present in high amounts in thymus and lymph nodes of all the species except for rabbits. Conversely, heparin was not detected in brains of all the species and also in none of the rabbit tissues. Based on this characteristic distribution the possible physiological role of heparin is discussed.     

Effects of granulocyte colony-stimulating factor (G-CSF) treatment on granulocyte function and receptor expression in patients with ventilator-dependent pneumonia

Adiabatic pulses, although useful in generating uniform spin nutation in the presence of inhomogeneous B1 fields, are limited for NMR imaging applications due to the lack of slice-selective excitation capability. Selective excitation techniques using gradient modulation have been introduced; however, present methods require either a minimum of two excitations or eight adiabatic segments. Here, a scheme is presented that allows single-shot, arbitrary flip-angle, and slice-selective excitation with only four adiabatic half-passage segments. The technique is demonstrated via computer simulation and experimental tests on a phantom. Furthermore, issues associated with the implementation of these gradient-modulated adiabatic pulses are discussed.     

Thirty-day mortality and long-term survival following surgery for prosthetic endocarditis: a study from the UK heart valve registry

Age of onset of schizophrenia (AOS) may be largely determined by neurobiological factors. We examined in a diverse sample of schizophrenia out-patients the relationships of AOS with neuropsychological abilities and structural brain abnormalities as measured on cerebral magnetic resonance imaging (MRI). A total of 82 out-patients meeting DSM-III-R criteria for schizophrenia were evaluated with a comprehensive neuropsychological battery and semi-automated quantitatively analysed cerebral MRI. Earlier AOS correlated with poorer performance in learning and abstraction/cognitive flexibility, and with larger volumes of caudate and lenticular nuclei, and smaller volume of thalamus on MRI. A model for predicting AOS consisting of abstraction and thalamic and caudate volumes remained significant after controlling for duration of illness, current age and daily neuroleptic dose. In conclusion, AOS may be related to specific rather than general measures of cognitive performance and structural brain abnormalities.