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Biomedical subjects

B Guerrero

Publications and source records attributed to B Guerrero.

At least 19 recordsLinked to original sources
PubMed2004

Immersion and emotion: their impact on the sense of presence.

The present study is designed to test the role of immersion and media content in the sense of presence. Specifically, we are interested in the affective valence of the virtual environments. This paper describes an experiment that compares three immersive systems (a PC monitor, a rear projected video wall, and a head-mounted display) and two virtual environments, one involving emotional content and the other not. The purpose of the experiment was to test the interactive role of these two media characteristics (form and content). Scores on two self-report presence measurements were compared among six groups of 10 people each. The results suggest that both immersion and affective content have an impact on presence. However, immersion was more relevant for non-emotional environments than for emotional ones.

Adolescent↗
PubMed2002

Use of aminoglutethimide in the treatment of pituitary-dependent hyperadrenocorticism in the dog.

The aim of this study was to evaluate the efficacy and safety of aminoglutethimide in the treatment of dogs with pituitary-dependent hyperadrenocorticism (PDH). Ten dogs were diagnosed with PDH based on clinical and laboratory data, adrenal function tests (adrenocorticotropic hormone [ACTH] stimulation test and urinary cortisol/creatinine ratio [UCCR] combined with a high dose oral dexamethasone suppression test) and ultrasonographic evaluation of the adrenal glands. Aminoglutethimide was administered daily at a dose of 15 mg/kg bodyweight for one month. Median basal cortisol concentration and post-ACTH cortisol concentration one month after treatment were significantly lower than pretreatment values. Complete response was achieved in one dog, and partial response was obtained in three dogs. Severe side effects of anorexia, vomiting and weakness occurred in one dog and medication was withdrawn. Two further dogs developed decompensations of concurrent diseases and medication was stopped in these animals as well. Mild toxicity occurred in four dogs. Moderate to severe elevations in liver enzymes occurred in all dogs. The efficacy of this drug is lower than that observed using mitotane and ketoconazole, and adverse effects limit its use. Aminoglutethimide, using the protocol described, cannot be recommended for long-term management of PDH in the dog.

Adrenal Glands↗
PubMed2001

Thrombolytic effect of lonomin V in a rabbit jugular vein thrombosis model.

Thrombolytic efficacy of lonomin V (LV), a protein isolated from Lonomia achelous caterpillars haemolymph, administered either as a single intravenous bolus or as a continuous infusion, was evaluated in a rabbit jugular vein thrombosis model, and compared with those of single-chain tissue-type plasminogen activator (sct-PA) and two-chain urokinase-type plasminogen activator (tcu-PA). As a bolus LV, at doses of 100 000 IU/kg body weight (bw) produced an activator-induced thrombolysis (AIL) of 50.94% +/- 12.4 compared with 14.4% +/- 10.8 for tcu-PA at the same dose. As a continuous infusion at doses of 200 000 IU/kg bw LV produced an AIL of 45.8%, whereas sct-PA and tcu-PA produced an AIL of 69.9 and 33.7%, respectively. Fibrinogen, plasminogen and alpha-2-antiplasmin levels decreased significantly with the higher doses of LV, sct-PA, and tcu-PA. Factor XIII levels were significantly reduced in a dose-dependent manner only with LV. In conclusion, LV produces a dose-dependent thrombolysis in combination with a decrease in factor XIII activity.

Animals↗
PubMed1999

Effect on platelet FXIII and partial characterization of Lonomin V, a proteolytic enzyme from Lonomia achelous caterpillars.

Contact with Lonomia achelous caterpillars venom induces a severe bleeding syndrome in humans. A constant finding in all reported cases is a marked decrease of blood coagulation factor XIII (FXIII), which has been attributed to the presence of a proteolytic enzyme, isolated and named Lonomin V, in the hemolymph and hair secretion. In this study, the effect of Lonomin V on transglutaminase activity from human plasma, rabbit plasma, and platelet FXIII was analyzed. The decrease of activity was more pronounced in platelet (A2) when compared with rabbit plasma (AB) and human plasma FXIII (A2B2). This finding might be explained by the differences in FXIII molecular structure. In addition, platelet FXIII molecule was degraded by Lonomin to several fragments of low molecular mass. Lonomin V was stable over a wide range of pH (6-8.5) and temperatures of -70 degrees C, -20 degrees C and between 4 to 24 degrees C, with a progressive decrease at 37 degrees C and total inactivation at 60 degrees C after 2 hours incubation. Diisopropyl fluoro-phosphate, phenylmethylsulfonyl fluoride, tosyl-l-lysine chloromethyl ketone, and iodoacetamide abolished the effect of Lonomin V on FXIII; in contrast dithiothreitol and EDTA-Na enhance the activity. We concluded that Lonomin V is a serine proteinase with a free Cys essential for the enzymatic activity. Due to its proteolytic activity on FXIII, with concomitant impairment of fibrin cross-linking, Lonomin V might be useful in association with thrombolytic drugs for preventing rethrombosis.

Animals↗
PubMed1999

The action of Lonomia achelous caterpillar venom on some blood coagulation and fibrinolysis parameters of the rabbit.

The bodily secretions of the Lonomia achelous caterpillar cause a severe and often fatal acquired bleeding diathesis in humans. The rabbit was selected as model animal in an attempt to understand the mode of action of the venom. The animals were injected subcutaneously with either hemolymph or chromatographically purified fractions. Injections of hemolymph produced a drop in fibrinogen and factor XIII levels and an increase in fibrinogen degradation products (FDP). In addition one batch of hemolymph decreased plasminogen levels. The chromatographically semipurified fraction II decreased both fibrinogen and plasminogen. The effect was dose dependent but, unlike in humans, there was a fairly rapid return to baseline values. In conclusion, the response to Lonomia achelous venom in the rabbit is similar to the response seen in humans, but with a more rapid recovery.

Animals↗
PubMed1999

Invertebrate compounds acting on the hemostatic mechanism.

Physiological secretions from some invertebrates have toxic effects on mammalian blood coagulation and fibrinolytic systems. Some of these effects occur because the substances contained in the secretions resemble the components of the hemostatic system. Some of the substances have been characterized, and have been found to have similar molecular weights or sequences, which may indicate a common ancestry. The components can be divided into five groups: antithrombic agents (group I); inhibitors and activators of the prothrombinase complex (group II); substances that affect platelet function (group III); substances that affect the fibrinolytic mechanism (group IV); and a group of miscellaneous agents whose activities are difficult to group together (group V). In group I special mention of the antithrombin agents in Hirudo medicinalis should be made. In group II, the agents affecting the prothrombinase complex are antistasin from Haementeria officinalis, ghilanten from Haementeria Ghiliani and the tick anticoagulant protein from Ornithodoros moubata, a factor V activator/inhibitor from Lonomia achelous and factor II and factor X activators from L. achelous and Lonomia obliqua. Examples of factors which affect platelet function (group III) are glossina from the black fly Glossina morsitans, calin from H. medicinalis, decorsin (a desintegrin) from Macrobdella decorsa, and FAGA from Stichopus japonicus selenka. The first three of these are inhibitors of platelet aggregation, and the last is an inducer. The plasminogen activators (group IV) from the L. achelous caterpillar and Eutriatoma maculata trigger the fibrinolytic system, whereas hementin from H. officinalis and hementerin from Haementeria depressa are directly fibrinolytic. The last group of substances (group V) include those with factor-XIIa-like activity from D. farinae, kallikrein-like activity and a factor XIII degrading enzyme from L. achelous, destabilase from H. medicinalis and prolixin S (nitroforin 2, or anti-factor-IXa) from Rhodnius prolixus. Some of these components have been well characterized, cloned and prepared in recombinant form, and seem to be very promising from the therapeutic point of view.

Animals↗
PubMed1998

[Vitamin K: biochemistry, function, and deficiency. Review].

Vitamin K is a cofactor for the synthesis of blood coagulation Factors II, VII, IX and X, and inhibitors such as Protein C and S and bone matrix protein. Its active form is a coenzyme in the glutamic acid carboxylation. Vitamin K-dependent factors form enzymatic complexes with calcium and membrane phospholipids. The insufficiency of gamma glutamic carboxylation impairs the hemostatic function. Hereditary deficiencies, antibiotics and oral anticoagulants, decrease the capacity of complex formation giving way to hemorrhage or thrombosis, or bone mass disturbances which are easily treated with administration of Vitamin K. The main causes of Vitamin K deficiency are lack of hepatic storage in newborns, liver insufficiency, malabsorption, dietetic deficiency, therapy with the antibiotics and coumarin administration. For the study of Vitamin K there are methods to measure the Vit K dependent proteins and as well methods to measure specifically the quinonas.

Adult↗
PubMed1992

Activation of human prothrombin by the venom of Lonomia achelous (Cramer) caterpillars.

In this paper, we demonstrated that the procoagulant action of Lonomia achelous (Cramer) is due in part to a component that activates prothrombin. The activation by crude venom and Fractions obtained by gel filtration on Sephadex G-75 is not dependent of phospholipid, Ca++ or Factor V. The activation of prothrombin by Fraction I is greatly stimulated by Factor V in the presence of phospholipid and Ca++; in presence of SBTI, we found that the Fraction I and Factor Xa act in a similar manner. These results suggest that the Fraction I is a Factor Xa - like prothrombin activator.

Animals↗
PubMed1992

Six new cases of a caterpillar-induced bleeding syndrome.

We describe six new cases of a hemorrhagic diathesis induced by contact with Lonomia achelous caterpillars. Onset of clinical bleeding varied between a few hours and 10 days post-exposure. Laboratory coagulation tests showed prolonged PT, PTT and ThT; normal platelets and a marked decrease of fibrinogen, factor V, plasminogen and factor XIII (including its subunits A and S). Factors VII, II and alfa 2 anti-plasmin were variably affected. In addition, activation of the fibrinolytic system and the generation of a procoagulant effect could also be demonstrated. Two cases developed severe hemorrhagic diathesis and one of them died of a cerebral hemorrhage. Different aspects of this rare syndrome are discussed in relation to its complex physiopathology and the variability observed in all clinical and laboratory manifestations. Therapeutic recommendations and some possible hazards following replacement transfusions are also considered.

Adult↗
PubMed1988

New insights on the mode of action of intrauterine contraceptive devices in women.

To gain a better understanding of the mechanism of action of intrauterine devices (IUDs), a search was made for ova in the genital tracts of 115 women using no contraception and of 56 women using IUDs, all of whom volunteered for study in conjunction with surgical sterilization. Ova were recovered from tubal flushings between 48 and 120 hours after the midcycle peak of luteinizing hormone in 39% of the IUD users compared with 56% of women in the control group (0.05 less than P less than 0.10). This suggests an action of the IUD before the ovum reaches the uterus. Eggs with a microscopic appearance consistent with fertilization were recovered from the fallopian tubes of half of the women using no contraception who had intercourse within the fertile period of the reproductive cycle and from whom ova were recovered. In contrast (P less than 0.01), no eggs with this appearance were recovered in IUD users who had intercourse within the fertile period. No ova were recovered from the body of the uterus of any of the IUD users. Fertilized ova are less likely to reach the uterine cavity containing an IUD. Thus, the principal mode of IUDs is by a method other than destruction of live embryos.

Fallopian Tubes↗