Biomedical subjects

L G Roda

Publications and source records attributed to L G Roda.

At least 19 recordsLinked to original sources

PubMed2003

Dehydroepiandrosterone metabolism in human plasma.

The possibility that dehydroepiandrosterone (DHEA) is metabolized in human plasma was studied by column and thin-layer chromatography. The results obtained indicate that a time-dependent disappearance of DHEA is matched by the appearance of newly-formed species that may represent DHEA conversion by-products. Neither disappearance of DHEA, nor formation of the alleged conversion by-products was observed when reactions were performed under conditions in which plasma enzymes were removed or inactivated. These results suggest that, in plasma, DHEA is partially transformed into different substances, and that the conversion reactions are catalyzed by enzymes present in this tissue. The observed kinetics of appearance and partial disappearance of the radiolabeled species can be interpreted as indicating that some of the by-products formed are further converted into other substances. The data shown appear to indicate that plasma can be added to the list of the already known compartments that are involved in steroid metabolism.

Adult↗

PubMed2001

Neuropeptide degradation in naive and steroid-treated allergic saliva.

The hydrolysis of neuropeptides and possible variations in hydrolysis following steroidal treatment, were examined in the presence of saliva collected from allergic volunteers; data obtained were compared to those obtained with a age and sex-matching group of healthy controls. The results reported indicate the presence of a statistically significant increase in the hydrolysis of the model substrate in allergic as compared to control saliva, and a reduction of substrate hydrolysis in treated as compared to naive allergic saliva. Total enzyme activity, the relative activity of the three classes of substrate-active enzymes (aminopeptidases, dipeptidylaminopeptidases, and dipeptidylcarboxypeptidases), the allergy-associated variations of these activities, and the variations associated to therapy were found to be different in male and female saliva. Specifically, in the controls, the lower level of hydrolysis evident in female as compared to male saliva appeared to be principally induced by lower activity of aminopeptidases. Under allergic conditions, a sex-different increase in the activity of all three classes of substrate-active enzymes modified the hydrolysis pattern differently in samples obtained from male and female donors. Finally, pharmacological treatment induced opposite effects on the enzymes present in each sex: in male saliva, the activity of all three classes of substrate-active enzymes--and, thus, of substrate hydrolysis--was reduced near to the levels measured in the controls. In female saliva, the reduction in the activity of aminopeptidases was coupled with an increase in the activity of dipeptidylaminopeptidases, causing substrate hydrolysis to remain near the levels measured in naive allergic, rather than control, saliva.

Adult↗

PubMed2000

Neuropeptide enzyme hydrolysis in human saliva.

The possible hydrolysis of neuropeptides by human saliva was studied using leucine enkephalin as a model. The data obtained indicate that in the presence of saliva this substrate is partially hydrolysed, and that its disappearance corresponds to the appearance of peptides whose composition is consistent with that of the substrate hydrolysis by-products. The formation of these peptides indicates the presence of all three classes of enzymes known to hydrolyse enkephalins in other tissues: aminopeptidases, dipeptidylaminopeptidases and dipeptidylcarboxypeptidases. The activity of these enzymes appears to be altered by the presence of low molecular-weight substances, whose inhibitory activity is apparent on all three classes of enkephalin-degrading enzymes. Substrate degradation was higher in male than female saliva; these differences appear to be caused by lower activity of the enzymes, and higher activity of the low molecular-weight inhibitors, measurable in female as compared to male saliva.

Adult↗

PubMed2000

Enkephalin-degrading enzymes and their inhibitors in human saliva.

The possible presence of enzymes able to hydrolyze leucine enkephalin has been investigated in human saliva. The data obtained indicate that, in the presence of saliva, Leu-enkephalin is partially hydrolyzed. The disappearance of the substrate is paired with the formation of hydrolysis byproducts whose composition indicates the presence of all three classes of enzymes known to hydrolyze enkephalins: aminopeptidases, dipeptidylaminopeptidases, and dipeptidylcarboxypeptidases. The presence of low molecular weight substances with inhibitory activity on proteolytic enzymes has also been detected. These substances are active on all three classes of enkephalin-degrading enzymes, although the inhibition is more evident on dipeptidylpeptidases than on aminopeptidases. Substrate degradation was found to be higher in male than in female saliva: this seems to be caused by the activities both of enzymes and low molecular weight inhibitors that are different in the two sexes.

Adult↗

PubMed1999

Hydrolysis of peripheral leucine enkephalin in allergic asthma.

Plasma hydrolysis of leucine enkephalin was studied in a group of patients affected by seasonal allergic asthma in acute and quiescent stage; data were compared with those obtained from a control group of healthy volunteers. Results obtained indicate a statistically significant reduction of leu-enkephalin hydrolysis in allergic subjects. In the quiescent stage, substrate degradation is reduced, and the pattern of the hydrolysis by-products is modified with respect to normal controls. In the acute stage, hydrolysis is further reduced, and the pattern of the hydrolysis by-products is further modified with respect to the quiescent stage. The variations of leu-enkephalin hydrolysis appear to be controlled by decreased activity of proteolytic enzymes and by increased activity of the low-molecular-weight plasma inhibitors active on these enzymes. The sum of these processes is conducive to a distribution of enkephalin-hydrolyzing enzymes, as well as a hydrolysis pattern, that appears to be specific for the allergic subjects and distinct from that seen in the controls.

Acute Disease↗

PubMed1999

Trauma decreases leucine enkephalin hydrolysis in human plasma.

Plasma hydrolysis of leucine enkephalin was evaluated, together with several cellular immune parameters, in a homogeneous group of human subjects who had undergone severe trauma (proximal femur fracture); data obtained were compared with those obtained in an age-matched control group. In the experimental group, immediately after hospitalization, substrate hydrolysis was reduced with respect both to the control subjects and the same patients 4 weeks after the trauma. Chromatographic separation of the enzymes active on leu-enkephalin showed that the reduction of substrate hydrolysis is mainly attributable to the decrease in the activity of enkephalin-degrading enzymes, principally of aminopeptidases, per se, whereas the role of the low-molecular-weight plasma inhibitors is only minor. In the same subjects, several of the immunological parameters measured underwent modifications that may be considered stress related. However, the absence of a quantitative relationship between reduction in hydrolysis and modifications of immune parameters does not support the hypothesis of a direct relationship between these two sets of data.

Aged↗

PubMed1998

Leucine enkephalin degradation in allergopathic versus normal human plasma.

The enzyme hydrolysis of labelled leu-enkephalin in the presence of plasma enzymes was studied by kinetic and chromatographic techniques in a group of allergopathic patients in the acute and quiescent stage; data obtained have been compared with those obtained with normal controls. Results shown indicate that in the quiescent stage substrate degradation is reduced, and that the pattern of the hydrolysis by-products is modified with respect to the controls. In the acute as compared to the quiescent stage, enkephalin hydrolysis is further reduced, and the pattern of hydrolysis by-products is further modified. ANOVA analysis of these data indicates that the dependency of hydrolysis reduction upon the grouping of subjects (i.e., controls, quiescent and acute stage) is statistically very significant. Reduced substrate hydrolysis, and modified hydrolysis pattern, appears to be associated with decreased activity of the enzymes involved and more significantly with increased activity of the low molecular weight plasma inhibitors. The combination of these two factors appears to define a hydrolysis pattern characteristic of the allergopathic subjects, similar in the quiescent and acute phase, and different from that observed in the controls.

Adolescent↗

PubMed1998

Age-induced increase of leucine enkephalin enzyme degradation in human plasma.

Possible age-induced variations of the hydrolysis of leucine enkephalin in the presence of plasma enzymes were studied by kinetic and chromatographic techniques in a group of elderly individuals. Results obtained indicate that in elderly individuals the activity of enkephalin-degrading plasma enzymes is greater than in the controls; ANOVA analysis of these data indicates that the dependency of the variation of hydrolysis upon the two age groups is statistically significant. Increased substrate hydrolysis, and a modified hydrolysis pattern, appear to be associated with increased activity of the enzymes involved, and with different distribution of the individual enzymes within each class, as well as with severely reduced activity of the low molecular weight plasma inhibitors. The combination of these factors defines a characteristic hydrolysis pattern for the elderly individuals, different from that found in the controls.

Adult↗

PubMed1997

Interindividual variability of enkephalin-degrading enzymes in human plasma.

The interindividual variability of the hydrolysis of leucine enkephalin, and of the formation of its hydrolysis by-products has been studied in human plasma. In agreement with known data, the data obtained indicate that Leu-enkephalin is degraded by several enzymes, belonging to three classes: aminopeptidases, dipeptidylaminopeptidases, and dipeptidylcarboxypeptidases. The relative ratio of the substrate degraded by each enzyme class-as well as the expression of the single enzyme species within each class-appears to be individually determined. Interindividual variability observed seems controlled by two main factors: the pattern of enkephalin-degrading enzymes and, more notably, the low molecular weight plasma inhibitors. Both these factors appear to be partially specific of each donor. Possibly because of the composition of these factors, the hydrolysis pattern of the substrate is characteristic of each donor, and constant in blood obtained from successive drawings, at least within a relatively short period of time.

Adult↗

PubMed1997

Effect of differentiation on the leucine enkephalin-degrading soluble enzymes released by the K562(S) cell line.

Leu-enkephalin hydrolysis kinetics were measured in the presence of soluble supernatants obtained from cultures of the K562(S) leukaemic cell line. Under these conditions, the substrate is degraded with formation of two distinct patterns of the hydrolysis by-products: in one pattern, similar amounts of Tyr and Tyr-Gly are formed; in the other, only Tyr-Gly can be measured. Kinetic data suggest that soluble proteolyses are released by these cells, and that either dipeptidylaminopeptidases alone, or both aminopeptidases and dipeptidylaminopeptidases are involved in substrate hydrolysis. This alternation of hydrolysis patterns appears consistent with existing data on the heterogeneity of K562 cells. In contrast with these results, chromatographic separation of the soluble enzymes indicates the release of all three classes of proteolyses known to hydrolyze enkephalins: aminopeptidases, dipeptidylaminopeptidases and dipeptidylcarboxypeptidases. In cells induced to differentiate by treatment with butyric acid, substrate hydrolysis is increased, and the pattern of the enzymes released is modified. In these cells, variations in both total proteolytic activity, and ratio between the three enzyme classes mentioned above are only minor, while the ratio between the different enzyme species within each class is greatly modified. Data obtained suggest that the expression of soluble enzymes is modified by differentiation. These data may also be interpreted as stressing the role of competition in controlling substrate hydrolysis by the multiple enzymes co-released by K562(S) cells.

Cell Differentiation↗

PubMed1996

Conformational study of [Met5]enkephalin-Arg-Phe in the presence of phosphatidylserine vesicles.

The interaction of [Met5]enkephalin-Arg.Phe with phosphatidylserine (PtdSer) was studied by circular dichroism (CD), two-dimensional nuclear magnetic resonance spectroscopy, hybrid distance geometry simulated annealing (DG-SA) and molecular dynamics (MD) calculations. The very low solubility of [Met5]enkephalin-Arg-Phe and the instability of the solution containing PtdSer vesicles at low pH values did not allow us to observe the amide proton resonances in the usual two-dimensional NMR work. NOESY cross-peaks of protons of side chains from two-dimensional NMR were converted into distances which were used as restraints for modelling with DG-SA and MD. Our results indicate that, in aqueous solutions at pH 7.68 [Met5]enkephalin-Arg-Phe exists in the absence of PtdSer as a random distribution of conformers, whereas in the presence of PtdSer it adopts conformations containing a common orientation of the bonds of C alpha 2, C alpha 3, C alpha 4, and C alpha 5, although different orientations of the peptide planes are consistent with the results. Two of the reported conformers from MD simulations are characterized by the presence of a 2<--4 gamma and inverse gamma turns centered on Gly3. A gradual decline of order was observed when moving from the central moiety of the peptide to both the N-terminus and C-terminus. Finally, the DG-SA and MD calculations resulted in a structure such that the orientation of the Phe4 and Met5 side chains favours hydrophobic interactions with the apolar portion of the PtdSer vesicle to form a hydrophobic cluster. These data support the hypothesis of a role of lipids to modify the conformation of [Met5]enkephalin-Arg-Phe to permit the interactions with the receptor site.

Amino Acid Sequence↗

PubMed1996

Role of enzymes and inhibitors in leu-enkephalin metabolism in rabbit and human plasma.

The hydrolysis of leucine enkephalin by the proteolytic enzymes present in human and rabbit plasma has been studied by kinetic and chromatographic techniques. Data obtained indicate the existence of noticeable intraspecific differences in the kinetics of leu-enkephalin degradation, and of formation of its hydrolysis by-products. The separation of the enzymes active on the substrate and of the inhibitors active on these enzymes evidences the existence of a species specific distribution of both groups of substances. Yet, the dissimilar kinetics of the substrate hydrolysis and of formation of its hydrolysis by-products appear to arise more from diversities in the competition between the enzymes present in plasma and in the role of inhibitors than from the differences in the enkephalin-degrading enzymes. It is suggested that differences observed may be related to the existence of species specific populations of the information-carrying plasma peptides.

Animals↗

PubMed1996

Positive and negative immunomodulation by opioid peptides.

The data that follow review part of the existing evidence concerning the neuroimmune functions mediated by opioid peptides, with particular regard to dual immunomodulatory effects. Limited references to substances other than opioid peptides are included, mainly to emphasize the possible similarities in the mediation of neuroimmune interactions by different informational substances, while the interactions directed from the immune to the nervous system have deliberately been omitted.

Adjuvants, Immunologic↗

PubMed1996

Specificity of proteolysis inhibitors in rabbit plasma.

Hydrolysis and inhibition of hydrolysis of leucine enkephalin in Oryctolagus plasma were studied by kinetics and chromatographic techniques. By data obtained, in this species, enkephalins are degraded by the same enzymes active in other mammals: aminopeptidases, dipeptidylaminopeptidases, and dipeptidylcarboxypeptidases. At variance with data obtained in other species, where enkephalins are hydrolyzed mostly by aminopeptidases, in Oryctolagus Leu-enkephalin hydrolysis is mainly due to dipeptidylcarboxypeptidases, whereas aminopeptidases contribution is the minimum of all three enzyme groups. Comparative analyses performed in the presence and in the absence of plasma inhibitors indicate that the ability of these substances to reduce substratum hydrolysis is very limited. On the contrary, the specific hydrolysis pattern evidenced appears to originate primarily from selective inhibition of the three groups of enzymes. Results obtained appear consistent with a role of plasma inhibitors in tuning hydrolysis to specific substrata, without appreciably modifying the amount of the substratum degraded.

Aminopeptidases↗

PubMed1995

Enzymes and inhibitors in leu-enkephalin in metabolism in human plasma.

The enzymes degrading leucine enkephalin in human plasma and the inhibitors active on these enzymes were studied by kinetic and chromatographic techniques. Data obtained evidence the existence of complex kinetics of leu-enkephalin hydrolysis and of formation of its hydrolysis by-products. These appear to originate from the combined effect of further hydrolysis of the enkephalin's fragments after their release and of competition between the different enzymes present in plasma. Chromatographic separation of plasma proteolysis inhibitors indicates the existence of several pools of substances acting on all three enzyme groups that degrade leu-enkephalin. The partial specificity of these substances induces competition effects: consequently, the actual protection over leu-enkephalin is considerably lower that the total inhibitory activity. That notwithstanding, plasma inhibitors control enkephalin hydrolysis to a relevant extent, while they modify only slightly the ratio of hydrolysis between the different enzymes. This latter parameter--and specifically the large prevalence of aminopeptidases over dipeptidylaminopeptidases and dipeptidylcarboxypeptidases--appears controlled mainly by kinetic factors.

Amino Acid Sequence↗

PubMed1994

Effect of differentiation on hydrolysis and association of Leu-enkephalin to K562(S) cells.

Hydrolysis of Leu-enkephalin and association to cells of the peptide-radioactive label have been studied on the K562(S) erythroleukemic cell subline. Data obtained indicate that in the presence of these cells, Leu-enkephalin is hydrolyzed, that the peptide's radioactive label is partially associated to cells, and that these phenomena are related. Hydrolysis and association are inversely modified by the cells' differentiation: hydrolysis is increased and association is decreased in differentiated compared with nondifferentiated cells. Moreover, the ratio of hydrolysis by-products is dissimilar between differentiated and nondifferentiated cells as a result of a significant modification of the soluble enzymes' release. The alterations induced by differentiation on all parameters investigated seem to indicate significant changes in the membrane structures responsible for the mechanisms controlling these phenomena.

Amino Acid Sequence↗

PubMed1993

Effect of stimulation on soluble proteolytic enzymes released by peripheral blood mononuclear cells.

The release of soluble peptidases active in the degradation of leucine enkephalin by human peripheral blood mononuclear cells (PBMC), and the effect of stimulation of mononuclear cells on the release of these enzymes are reported. Results obtained indicate that leu-enkephalin is partially degraded in the presence of soluble supernatants prepared from mononuclear cells. In accord with data previously obtained with immunocompetent cell lines, three classes of enzymes appear to be involved in leu-enkephalin hydrolysis: aminopeptidases, dipeptidylaminopeptidases and dipeptidylcarboxypeptidases. Phytohemagglutinin stimulation of mononuclear cells appears to cause a relevant increase of the total activity of the soluble enzymes, as well as a partial rearrangement of the ratio between the different enzyme activities. A similar effect is also evident upon chromatographic separation of the soluble supernatants: the relative activity of the several distinct enzymes--notably aminopeptidases and dipeptidylaminopeptidases--identified after column separation is significantly modified by PBMC stimulation. The effect of stimulation of mononuclear cells on the release of soluble enzymes can be interpreted as an indication of the role of these enzymes--possibly in the regulative process of informational peptides--similar to that described in the case of membrane enzymes.

Amino Acid Sequence↗

PubMed1993

Enkephalin-degrading dipeptidylcarboxypeptidases in human and Cavia porcellus plasma.

1. The dipeptidylcarboxypeptidases that degrade leucine enkephalin in human and guinea pig plasma were studied by kinetic and chromatographic techniques. 2. The extremely rapid degradation of enkephalins in Cavia plasma seems to be caused by both increased activity of enzymes and reduced role of inhibitors. 3. The increased role of dipeptidylcarboxypeptidases in Cavia as compared to Homo appears prevalently caused by the presence in the former species of a considerable number of very active enzymes. 4. The sum of these data indicates the existence of noticeable intraspecific differences either in peptide-degrading enzymes present in plasma, or in plasma peptides, or in both.

Amino Acid Sequence↗