Influence of age on the renal renin response to a high salt intake in the rat

Saline drinking combined with DOCA-treatment was found to decrease renal renin in weanlings at a higher rate than in adult rats, with a comparable saline consumption level. The decrease was not potentiated by uninephrectomy.     

Influence of age on epidermal growth factor receptor level in the rat brain

The influence of age on 125I-epidermal growth factor (EGF) binding to rat brain plasma membranes was investigated. The specific binding of EGF to membranes decreased gradually with age in both male and female rats. There was no significant difference in the specific binding between males and females. Scatchard analysis of the binding data showed that the decrease in EGF binding with age was due to a decrease in the number of EGF receptors.     

Influence of age on epidermal growth factor receptor level in the rat brain

Summary The influence of age on¹²⁵I-epidermal growth factor (EGF) binding to rat brain plasma membranes was investigated. The specific binding of EGF to membranes decreased gradually with age in both male and female rats. There was no significant difference in the specific binding between males and females. Scatchard analysis of the binding data showed that the decrease in EGF binding with age was due to a decrease in the number of EGF receptors.     

Radioprotective effect of a protein free parathyroid extract on the mitotic index of rat bone marrow cells.

The protective efficacy of an orally administered bovine protein-free parathyroid extract (PF-PTE) was studied on rat bone marrow cells in vivo with the mitotic index after 850 R irradiation. A remarkable decrease was found in the mitotic activity of bone marrow cells after irradiation in the non-protected animals. However, in the animals treated with PF-PTE after irradiation, a significantly smaller decrease and a faster recovery were found in the mitotic activity of the bone marrow cells.     

Radioprotective effect of a protein free parathyroid extract on the mitotic index of rat bone marrow cells

Summary The protective efficacy of an orally administered bovine protein-free parathyroid extract (PF-PTE) was studied on rat bone marrow cells in vivo with the mitotic index after 850 R irradiation. A remarkable decrease was found in the mitotic activity of bone marrow cells after irradiation in the non-protected animals. However, in the animals treated with PF-PTE after irradiation, a significantly smaller decrease and a faster recovery were found in the mitotic activity of the bone marrow cells.     

Possible involvement of indolamines in the glycogenic effect of the convulsant methionine sulfoximine in rat brain.

The aim of the present investigation was to look for the mechanisms causing disturbances in carbohydrate metabolism during the action of the epileptogenic agent methionine sulfoximine. The levels of glucose, glycogen, and indolamines were measured in seven different regions of rat brain. Methionine sulfoximine induced a decrease in serotonin level which was roughly dose-dependent. There were no obvious changes in tryptophan and 5-hydroxyindoleacetic levels in any area. Methionine sulfoximine induced the known increase in glucose and glycogen levels. The direct precursor of serotonin. 5-hydroxytryptophan, and benserazide (a decarboxylase inhibitor) were then injected into rats in association with methionine sulfoximine. In this case, methionine sulfoximine failed to induce seizures. Moreover, the serotonin level was unchanged and the carbohydrate content did not significantly increase. There was only a rise in 5-hydroxyindoleacetic acid level. This work shows a striking parallelism between serotonin decrease and glycogen increase.     

Circulating Trypanosoma cruzi from the same cloned population show differences in the ability to infect cells and to cause lethal infection in mice

Two subpopulations of circulating parasites displaying different abilities to infect mammalian cells and to cause lethal infection when inoculated into normal mice were demonstrated in the blood of mice acutely infected with T. cruzi. Parasites of one subpopulation rapidly penetrated mouse fibroblasts and were readily phagocytized by normal mouse peritoneal macrophages whereas parasites of the other subpopulation showed little ability to invade non-phagocytic cells and resisted phagocytosis. Inoculation of organisms of this latter population into mice resulted in infections with lower parasitemias and longer time to death as compared to controls inoculated with organisms from a population containing both types of parasites. When a population of parasites containing both types of trypanosomes was cultured in acellular medium at 28 degrees C a decrease in the number of parasites was noted to occur in the initial days of culture. This decrease was not noted when parasites of the subpopulation of trypanosomes resistant to phagocytosis were cultured similarly.     

A turbidimetric method for the screening of amylase-producing mutants of Aspergillus niger

Summary The method is based on the assumption that extracellular amylase, which is produced by strains ofAspergillus niger in liquid culture, hydrolyses the starch in the media and brings about a corresponding decrease in the turbidity of the media. Mutant strains which produced different quantities of amylase exhibited different degrees of decrease in turbidity of the media. The results showed that a greater degree of decrease in turbidity was observed for a higher quantity of amylase produced.     

The role of the substantia nigra on the rage reaction elicited by hypothalamic stimulation, in the cat

The effects of substantia nigra stimulation on the rage reaction evoked by hypothalamic activation were studied. The reference value of the rage reaction was the latency of the hissing, which was constant in all animals when hypothalamic stimulation was performed with the same parameters. Simultaneous activation of substantia nigra and hypothalamus determined a significant decrease in hissing latency. The influence of the substantia nigra on the affective components of the aggressive behavior is underlined.     

Cell-to-cell communication in the heart: structure-function correlations

The communicating cell junctions that ensure the electrical and diffusional continuity of the intracellular space in the heart fibres can be switched from their normal conducting, or opened state, to an exceptional non-conducting, or closed state. This electrical uncoupling is observed after cell injury in the presence of Ca2+ ions in the extracellular fluid, after metabolic inhibition and in the presence of aliphatic alcohols (C6 to C9). The correlations between electrical uncoupling and gap junction morphology in the heart are briefly reviewed. A decrease of the distance between P-face particles and between the E-face pits has been found in all investigations, but the functional significance of this observation is not understood at present. A quantitatively very similar decrease of the average particle diameter (about -0.7 nm) has been measured in glutaraldehyde-fixed sheep Purkinje fibres and in unfixed, quickly frozen rat auricles that had been electrically uncoupled by three different procedures. About half of this decrease was reversible on short-term electrical recoupling (within 20 min). It is concluded that a measurable decrease of the connexon diameter correlates with electrical uncoupling.     

E-cadherin and plakoglobin recruit plakophilin3 to the cell border to initiate desmosome assembly

A decrease in the levels of the desmosomal plaque protein, plakophilin3 (PKP3), leads to a decrease in desmosome size and cell-cell adhesion. To test the hypothesis that PKP3 is required for desmosome formation, the recruitment of desmosomal components to the cell surface was studied in the PKP3 knockdown clones. The PKP3 knockdown clones showed decreased cell border staining for multiple desmosomal proteins, when compared to vector controls, and did not form desmosomes in a calcium switch assay. Further analysis demonstrated that PKP3, plakoglobin (PG) and E-cadherin are present at the cell border at low concentrations of calcium. Loss of either PG or E-cadherin led to a decrease in the levels of PKP3 and other desmosomal proteins at the cell border. The results reported here are consistent with the model that PG and E-cadherin recruit PKP3 to the cell border to initiate desmosome formation.     

The role of the substantia nigra on the rage reaction elicited by hypothalamic stimulation,in the cat

Summary The effects of substantia nigra stimulation on the rage reaction evoked by hypothalamic activation were studied. The reference value of the rage reaction was the latency of the hissing, which was constant in all animals when hypothalamic stimulation was performed with the same parameters. Simultaneous activation of substantia nigra and hypothalamus determined a significant decrease in hissing latency. The influence of the substantia nigra on the affective components of the aggressive behavior is underlined.This work was supported by a grant from the Consiglio Nazionale delle Ricerche Roma, Italy.     

A quantitative interpretation of the metabolism-size relationship in animals

Summary Experimental studies with carp supported our hypothesis, that the regular decrease in the mass-specific rate of resting metabolism with increasing body mass may be explained principally by a combination of a decrease in the mass-specific rate of tissue metabolism, and an increase in the relative size of organs and parts of low metabolic activity with increasing body mass.     

Changes in the T4/T3 molar ratio following thyrotropin releasing hormone injection in cattle.

The injection of thyrotropin releasing hormone into cattle resulted in a rapid decrease in the T4/T3 molar ratio. 2 breeds of cattle, Shorthorn and Africander Cross were studied. The decrease in the T4/T3 molar ratio was significantly greater in the Shorthorn breed. It is concluded that acute stimulation of the thyroid gland with TRH results in enhanced release of both T3 and T4 and that T3 is discharged more rapidly than T4.     

Changes of the phosphatidylcholine content and the number of synaptic vesicles in relation to the neurohumoral transmission in sympathetic ganglia.

In sympathetic ganglia stimulated in the presence of HC-3, the reduction in number of synaptic vesicles was observed to be accompanied by a significant decrease of the ganglionic phosphatidylcholine content.     

Circadian rhythm of bile secretion in the rat.

In rats the bile flow and the estimated bile acid independant flow (BAIF) were significantly lower at 17.00 h than at 08.00 and 24.00 h. The decrease in BAIF paralleled the decrease in liver weight. Bile acid excretion was not different.     

Effects of retinoic acid on the fibrinolytic activity of HL 60 human promyelocytic leukemia cells

Summary Fibrinolytic activity of HL 60 human leukemic cells was found to increase in parallel with myeloid differentiation following retinoic acid but not dimethylsulfoxide treatment. However, both retinoic acid and dimethylsulfoxide produced an increase in acid phosphatase and a decrease in muramidase.     

Cell-to-cell communication in the heart: structure-function correlations

Summary The communicating cell junctions that ensure the electrical and diffusional continuity of the intracellular space in the heart fibres can be switched from their normal conducting, or opened state, to an exceptional non-conducting or closed state. This electrical uncoupling is observed after cell injury in the presence of Ca²⁺ ions in the extracellular fluid, after metabolic inhibition and in the presence of aliphatic alcohols (C₆ to C₉). The correlations between electrical uncoupling and gap junction morphology in the heart are briefly reviewed. A decrease of the distance between P-face particles and between the E-face pits has been found in all investigations^{3,10,16,18,55}, but the functional significance of this observation is not understood at present. A quantitatively very similar decrease of the average particle diameter (about –0.7 nm) has been measured in glutaraldehyde-fixed sheep Purkinje fibres¹⁶ and in unfixed, quickly frozen rat auricles¹⁸ that had been electrically uncoupled by three different procedures. About half of this decrease was reversible on short-term electrical recoupling (within 20 min). It is concluded that a measurable decrease of the connexon diameter correlates with electrical uncoupling.     

Effect of the rat liver S9 fraction on the mutagenicity of azathioprine in theSalmonella/mammalian microsome assay

Summary Azathioprine is a direct acting mutagen inSalmonella typhimurium TA100 and TA1535. Addition of rat liver S9 fraction with or without co-factors, or glutathione, causes a decrease in the mutagenicity of azathioprine in TA100 and an increase in TA1535, indicating the effect of SH groups.Acknowledgments. This work was supported in part by a grant from SECYT (Argentina).     

On the mechanism of the involvement of endothelium in reactive hyperemia

Experiments on anesthetized dogs and on vascular test-preparations demonstrated that reactive hyperemia (RH) was accompanied by the appearance of vasodilator in the blood, and that the level increased with the duration of occlusion of the artery. Removal of the endothelium of the part of the vascular bed studied using saponin, decreased the RH and relaxation of a test-preparation. A rise of pressure in the vascular bed, and a decrease in the deformability of the endothelium resulting from pretreatment with dimerized glutaraldehyde, affected both the hyperemia and the reaction of the vascular preparation in a similar way. It was concluded that the RH resulted from the secretion of vasoactive substances by the endothelium in response to a fall in intravascular pressure.