Microbial fibrinolytic enzymes: an overview of source, production, properties, and thrombolytic activity in vivo

Accumulation of fibrin in the blood vessels usually results in thrombosis, leading to myocardial infarction and other cardiovascular diseases. For thrombolytic therapy, microbial fibrinolytic enzymes have now attracted much more attention than typical thrombolytic agents because of the expensive prices and the undesirable side effects of the latter. The fibrinolytic enzymes were successively discovered from different microorganisms, the most important among which is the genus Bacillus from traditional fermented foods. The physiochemical properties of these enzymes have been characterized, and their effectiveness in thrombolysis in vivo has been further identified. Therefore, microbial fibrinolytic enzymes, especially those from food-grade microorganisms, have the potential to be developed as functional food additives and drugs to prevent or cure thrombosis and other related diseases.Dr. Yong Peng was invited by the editor-in-chief, Professor Dr. A. Steinbüchel, to write this review     

Iron absorption in the iron-deficient rat

Iron absorption in the iron-deficient rat was compared with that in the normal rat to better understand the regulation of this dynamic process. It was found that: Iron uptake by the iron-deficient intestinal mucosa was prolonged as a result of slower gastric release, particularly when larger doses of iron were employed. The increased mucosal uptake of ionized iron was not the result of increased adsorption, but instead appeared related to a metabolically active uptake process, whereas the increased mucosal uptake of transferrin iron was associated with increased numbers of mucosal cell membrane transferrin receptors. Mucosal ferritin acted as an iron storage protein, but its iron uptake did not explain the lower iron absorption in the normal rat. Iron loading the mucosal cell (by presenting a large iron dose to the intestinal lumen) decreased absorption for 3 to 4 days. Iron loading of the mucosal cell from circulating plasma transferrin was proportionate to the plasma iron concentration. Mucosal iron content was the composite of iron loading from the lumen and loading from plasma transferrin versus release of iron into the body. These studies imply that an enhanced uptake-throughout mechanism causes the increased iron absorption in the iron-deficient rat. Results were consistent with the existence of a regulating mechanism for iron absorption that responds to change in mucosal cell iron, which is best reflected by mucosal ferritin.     

The effect on some enzymes of rat tissue of diets low in fat content

1. Rats of two strains were kept on three different diets; one was a commercial diet of rat pellets, one contained about 80% of sucrose and 20% of casein and was supplemented with corn oil, and the third was a similar diet without the corn oil. 2. On the commercial diet, the specific activities of pyruvate kinase, glucose 6-phosphate dehydrogenase and fructose 1,6-diphosphatase in the livers of one strain of rats (strain A) were 1.5-3 times those in the other strain (strain B). When the diet high in sucrose and supplemented with corn oil was given, there were large increases in the specific activity of pyruvate kinase, glucose 6-phosphate dehydrogenase and fructose 1,6-diphosphatase in the livers of strain A rats. With strain B rats the increases were much smaller. Omission of corn oil from the diet caused a threefold increase in the specific activity of glucose 6-phosphate dehydrogenase in strain B rats, but had little effect on other enzymes. 3. The enzymes of the kidneys and hearts of strain A rats were also more active than those of strain B rats. In strain A rats, the specific activities of pyruvate kinase and fructose 1,6-diphosphatase in the kidney increased when the sucrose content of the diet was high, but in the kidneys of strain B rats there was little change. 4. In strain A rats, the specific activity of pyruvate kinase in the heart more than doubled with the high-sucrose-corn oil diet and increased threefold when corn oil was omitted. No changes were seen in strain B rats. 5. In strain A rats, omission of corn oil from the diet increased the ability of the kidneys to synthesize glucose from lactate. 6. In strain B rats, addition of corn oil to the diet resulted in a decrease in the liver in the specific activity of ATP citrate lyase and in the ability to incorporate acetate into lipid.     

Postradiation changes in the activity of membrane-bound nerve tissue enzymes

A study was made of the effect of various radiation doses (1.75 to 12.25 Gy) on the enzyme activity of Na,K-ATPase system of the microsomal brain fraction of mongrel and Wistar rats. With a similar method of the fraction isolation different response of the activity of this enzyme was registered. Different radiosensitivity of M9-ATPase is responsible for the direction of changes in the Na,K-ATPase activity of the preparations.     

The genetically epilepsy-prone rat: an overview of seizure-prone characteristics and responsiveness to anticonvulsant drugs

The Genetically Epilepsy-Prone Rat (GEPR) is rapidly gaining support as a model of epilepsy. In addition to a marked sensitivity to both sound-induced and hyperthermic seizures, GEPRs exhibit unusual sensitivity to a number of seizure-provoking modalities, including various forms of electrical and chemical stimulation. The existence of a moderate seizure colony (GEPR-3) and a severe seizure colony (GEPR-9) allows pathophysiological studies of seizure susceptibility and severity. The consistency of seizures within each colony allows for comparisons in seizure naive GEPRs and seizure experienced GEPRs. The consistent seizure responses of the GEPR are also ideal for the testing of anticonvulsant drugs. Further, the relative potencies of anticonvulsant drugs between the two colonies of GEPRs predict the clinical efficacies of traditional antiepileptic drugs and may be able to predict novel anticonvulsants.     

The significance of clinical assessment of brain tissue oxygenation in different pathological conditions: an overview.

The development of methods of measurement of brain oxygenation in man is reviewed and the possible clinical potential of some new and established laboratory techniques is evaluated. Advantages and problems associated with the various approaches are considered together with the difficulties that are encountered in interpretation of data obtained and the factors that may increase such difficulties. It is concluded that invasive techniques that can only be used intraoperatively are of limited value but may be helpful in confirming the edges of ischemic areas or the restoration of adequate local blood flow. Chronically implanted devices have been useful in detecting epileptic foci and in evaluation of anesthetic regimes in patients with brain lesions. Infrared spectroscopy may offer possibilities for noninvasive whole brain monitoring in patients, but the method lacks resolution.     

The taxonomy of rhizobia: an overview

The taxonomy of rhizobia, bacteria capable of nodulating leguminous plants, has changed considerably over the last 20 years, with the original genus Rhizobium, a member of the alpha-Proteobacteria, now divided into several genera. The study of new geographically dispersed host plants, has been a source of many new species and is expected to yield many more. Here we provide an overview of the history of the rhizobia, but focus on the Rhizobium–Allorhizobium–Agrobacterium relationship. Finally, we review recent reports of nodulation and nitrogen fixation with legume hosts by bacteria that are outside the traditional rhizobial phylogenetic lineages. They include species of Methylobacterium and Devosia in the alpha- Proteobacteria and of Burkholderia and Ralstonia in the beta-Proteobacteria.