Biomedical subjects

M J Gayoso

Publications and source records attributed to M J Gayoso.

At least 19 recordsLinked to original sources

PubMed2005

Specific dose-dependent damage of Lieberkühn crypts promoted by large doses of type 2 ribosome-inactivating protein nigrin b intravenous injection to mice.

Nigrin b is a non-toxic type 2 ribosome-inactivating protein as active as ricin at ribosomal level but 10(5) and 5 x 10(3) times less toxic for animal cell cultures and mice, respectively, than ricin. The purpose of the present study was to analyze the effects of intravenous injection of large amounts of nigrin b to the mouse. Injection through the tail vein of 16 mg/kg body weight killed all mice studied before 2 days. Analysis of several major tissues by light microscopy did not reveal gross nigrin b-promoted changes, except in the intestines which appeared highly damaged. As a consequence of the injury, the villi and crypt structures of the small intestine disappeared, leading to profuse bleeding and death. In contrast, intravenous injection of 5 mg/kg body weight was not lethal to mice but did trigger reversible toxic effects. In both cases, lethal and sub-lethal doses, the target of nigrin b appeared to be the highly proliferating stem cells of the intestinal crypts, which had undergone apoptotic changes. In contrast to nigrin b, the injection of 3 mug/kg of ricin kills all mice in 5 days but does not trigger apoptosis in the crypts. Therefore, the effect seen with sub-lethal nigrin b concentrations seems to be specific. Nigrin b killed COLO 320 human colon adenocarcinoma cells with an IC(50) of 3.1 x 10(-8) M and the effect was parallel to the extent of DNA fragmentation of these cells. Accordingly, despite the low general toxicity exerted by nigrin b as compared with ricin, intravenous injection of large amounts of nigrin b is able to kill mouse intestinal stem cells without threatening the lives of the animals, thereby opening a door for its use for the targeting of intestinal stem cells.

Animals↗

PubMed2003

Selective calcification of rat brain lesions caused by systemic administration of kainic acid.

Dystrophic calcification of previously damaged areas of nervous tissue occurs in a wide range of human diseases. The relationship between astroglial and microglial reactions and deposits of calcium salts was studied for up to five months in rats with a brain lesion produced by systemic administration of kainate. The morphology and atomic composition of the calcium salt deposits was also studied. Two types of lesions, sclerotic and liquefactive, were observed. In sclerotic lesions hyperplasia and hypertrophy of astrocytes partially substituted for the lost neurons, reaching a maximum in about twenty-five days after treatment. In liquefactive lesions, the astrocytic reaction occurred only around the liquefactive area. Microglial reaction was similar in both types of lesion and reached its highest expression in about twenty-five days. Calcium deposits were observed in the sclerotic but not in the liquefactive lesions. Clearly distinguishable granules of calcium salts were observed in sclerotic lesions under scanning electron microscopy after only five days post-injection. The size of calcified granules increased with time reaching 40 micro m or more in diameter at five months. The atomic composition of these deposits, studied by X-ray microanalysis, showed a time-dependent increase in calcium concentration. While there was no clear relationship between astroglial and microglial reactions and calcium salt deposits, the systemic injection of kainate produced progressively larger and more concentrated calcium deposits in sclerotic, but not in liquefactive lesions.

Animals↗

PubMed2003

Non-toxic type 2 ribosome-inactivating proteins (RIPs) from Sambucus: occurrence, cellular and molecular activities and potential uses.

Ribosome-inactivating proteins (RIPs) are a family of enzymes that trigger the catalytic inactivation of ribosomes. The most known member of the family is the highly poisonous two-chain ricin isolated from Ricinus communis L. Sambucus species contain a number of two-chain RIPs structurally and enzymatically related to ricin which have the noteworthy feature that, having an enzymatic activity on ribosomes, leading to the inhibition of protein synthesis, higher than ricin, they are lacking of the tremendous unspecific toxicity of ricin. Therefore, they have been called non-toxic type 2 RIPs. The most representative and studied members are nigrin b present in the bark of the common (black) elder Sambucus nigra L. and ebulin 1 present in the leaves of the dwarf elder Sambucus ebulus L. The molecular basis for the low unspecific activities of nigrin b and ebulin 1 as compared with ricin seems to be related with single changes of amino acids in the high affinity sugar binding sites of the B chains. These changes determine the intracellular traffic of these proteins and thus the cellular toxicity. Conjugation ofnigrin b or ebulin 1 to either transferrin or monoclonal antibodies provided highly active conjugates targeting cancer. Thus these non-toxic type 2 RIPs are promising tools for cancer therapy.

Amino Acid Sequence↗

PubMed2000

Effects of unilateral deprivation in postnatal development of the olfactory bulb in an altricial rodent, the gerbil (Meriones unguiculatus).

To establish if olfactory bulb sensitivity to functional deprivation is related to the degree of development at birth, we studied the effects of surgical closure of one naris in the gerbil olfactory bulb development. The naris closure was performed at three different ages: at birth, P7 and P14 and maintained for 30 or 60 days. In coronal sections we measured total bulbar surface area and surface area of the different bulbar layers establishing an estimate multiple regression model for the percentage of surface area decrease in the deprived bulb related to non deprived one. The internal and external plexiform layers are the most sensitive layers to deprivation and age and duration of deprivation were factors in their mathematical models. The glomerular layer showed a surface reduction of about 25% without dependence either on age or duration. The deprived glomerular layer showed a much lower tyrosine hydroxylase-immunoreactivity and immunoreactive cell density than those in the non deprived one. However, differences in calbindin-immunoreactive and NADPH-diaphorase positive cell density between deprived and non deprived glomerular layer were not significant. Our results indicate that olfactory bulb sensitivity to functional deprivation is not related to the degree of precocity and changes in age and duration of deprivation cause different effects on the olfactory bulb layers.

Animals↗

PubMed1998

Prenatal development of the mammalian vomeronasal organ.

The vomeronasal organ (VNO) originates from the medial wall of the olfactory pit shortly after the middle of the embryonic period in mammals. The Anlage stage consists of a cellular bud that grows dorsally, caudally, and towards the midline leaving a groove. The following stage, Early Morphogenesis, includes the closure of the vomeronasal groove to form a parasagittal blind-ended tube in the nasal septum, which opens into the nasal and/or oral cavities. The lumen adopts a crescent shape while the epithelial lining differentiates into an increasingly wider epithelium on the concave side and a gradually thinner epithelium on the convex side. The former goes on to occupy a medial position and develops neuroblasts among supporting and undifferentiated cells, with supporting cell nuclei tending to align in the upper rows. The lateral "non-sensory" epithelium furrows, giving a kidney-shaped appearance to the VNO cross section. The next stage, Late Morphogenesis is extended up to a difference in thickness between both epithelia becomes similar to the adult, generally by birth. An increasing number of ciliary generation complexes, larger and more abundant microvilli, and an evident glycocalyx are observed in the neuroepithelium at the luminal surface, while enzymatic activities become more intense. The non-sensory epithelium appears quite mature save for its luminal surface, which is still devoid of cilia. Blood capillaries penetrate the most basal region of the neuroepithelium and vomeronasal glands are very few and immature. At birth, some neurons appear well developed to support certain functionality; however, persistence of architectural, histochemical, and ultrastructural signs of immaturity, suggests that full performance of the VNO does not occur in newborn mammals, but in prepubertal ages.

Animals↗

PubMed1998

Paravertebral muscles in experimental scoliosis: a light and electron microscopic study.

Experimental structural dextroconvex scoliosis was produced in rabbits by costotransversolisis with transversectomy and releasing of paravertebral muscles between TVII and TX on the right side. Two compensatory curves developed on the upper dorsal and lumbar levels. Biopsies of paravertebral muscles in experimental animals included, besides areas of normal tissue, a considerable derangement of the cell contractile apparatus with sarcoplasmic dilation and eventual cell disintegration and necrosis. Histological changes varied along levels, the convexity being more affected. The severity of changes and reduction in body weight and length were correlated with the degree of scoliosis. A selective atrophy of slow-twitch fibers was observed in experimental animals, especially at the level of the main curve, whereas fast-twitch fiber atrophy was more important caudally. Control animal biopsies always appeared normal. Our experimental model shows an overt participation of paravertebral muscles in the establishment of compensatory processes following scoliosis, although the role that paravertebral muscles play in the etiopathogenesis of human idiopathic scoliosis requires further investigation.

Animals↗

PubMed1997

The role of retinotomy in an experimental rabbit model of proliferative vitreoretinopathy.

PURPOSE: To create a model of proliferative vitreoretinopathy (PVR) using retinotomy with vitrectomy, cryotherapy, and platelet-rich plasma (PRP) injection, which more closely resembles the human pathophysiologic condition. METHODS: One hundred and twenty albino rabbits were divided into 10 groups of 12 rabbits each and underwent the following procedures: group 1, vitrectomy; group 2, cryotherapy; group 3, PRP intravitreous injection; group 4, retinotomy; group 5, retinotomy and vitrectomy; group 6, retinotomy and cryotherapy; group 7, retinotomy and PRP injection; group 8, retinotomy, vitrectomy, and cryotherapy; group 9, vitrectomy, cryotherapy, and PRP injection and group 10, retinotomy, vitrectomy, cryotherapy, and PRP injection. All animals underwent follow-up examinations with indirect ophthalmoscopy and fundus photography on days 1, 3, 7, 10, 14, 21, and 28 after the procedure(s). Retinal changes were categorized according to the classification of Fastenberg et al. At the end of the experiments, the eyes were enucleated, and examined under light and electron microscopy. RESULTS: No retinal detachments (RDs) were observed in groups 1, 2, 4, 5, 6, and 8. RDs of varying severity were observed in group 3 (n = 1), group 7 (n = 2), group 9 (n = 6), and group 10 (n = 12). Light and transmission electron microscopy confirmed the findings. CONCLUSIONS: Combining retinotomy with vitreous removal, cryotherapy, and PRP injection creates an efficient and different model of PVR that produced RD in 100% of rabbit eyes.

Animals↗

PubMed1995

Effects of perinatal administration of haloperidol on GH pituitary contents and serum levels during the first postnatal month.

Perinatal dopaminergic blockade with haloperidol caused PRL increases in rat pituitary gland and serum which persisted during the first postnatal month. However the effects of dopamine on the synthesis and secretion of GH at these early ages are unknown. With the aim of investigating the effects of this blockade on postnatal GH secretion, haloperidol (1 mg/kg i.p.) was injected daily to pregnant rats from gestational day 16 until delivery and to pups from untreated mothers between postnatal days 2-6. GH pituitary contents and serum levels were measured weekly by RIA during the first postnatal month. The results showed that haloperidol induced a long-term increase in GH pituitary contents as well as a transient increase in serum levels. The results in serum are similar to those from human neonates indicating that dopamine plays a more important role as controller of the GH secretion in newborns than in adults.

Age Factors↗

PubMed1994

Brain lesions and water-maze learning deficits after systemic administration of kainic acid to adult rats.

The relationship between hippocampal damage and spatial learning deficiencies was studied in rats injected with kainic acid (10 mg/kg i.p.). A single injection was given either before or after the acquisition phase of the Morris water-maze task. In this acquisition phase, the animals were required to find a hidden underwater platform starting from four different points. The task was repeated twice a day for 10 days. In the retention phase after 10 days rest, the rats repeated the same task. The damage caused by the treatment occurred in several prosencephalic areas, including the piriform and enthorhinal cortices, the thalamus and the hippocampus. In the latter, greatest damage was seen in CA1 followed by CA3 while CA2 and the gyrus dentatus appeared almost unaffected. The behavioural results indicated that kainic acid impaired but did not preclude the acquisition of the water-maze task. During the retention phase, no significant differences in latencies were found between animals that were treated before and after acquisition, thus, indicating that pretraining does not play an important role in the recovery of these spatial abilities following hippocampal lesions.

Animals↗

PubMed1992

Intravitreal and subretinal proliferation induced by platelet-rich plasma injection in rabbits.

We developed an experimental model of proliferative vitreoretinopathy (PVR) in albino rabbits by combining some factors suspected of causing the disease. Sixty nine eyes divided into six groups served as controls (Groups C 1-6). Forty nine eyes were divided into four experimental groups (Groups E 1-4). Group E1 (n = 12) was injected with 0.15 ml of platelet-rich plasma. In addition, Groups E2 (n = 12) and E3 (n = 12) underwent cryotherapy or vitrectomy. Group E4 (n = 13) underwent both procedures. Seven of the 13 Group 4 experimental eyes developed total retinal detachment and giant holes. None of the other groups developed more than two total retinal detachments or giant holes (P < 0.05). Light and electron microscopy showed intravitreal or preretinal proliferation composed of fibroblast-like cells. Retroretinal membranes appeared only in Group E4 eyes, composed of elongated cells with oval nuclei and abundant organelles in the cytoplasm. We believe these lesions mimic human PVR more closely than other models previously developed.

Animals↗

PubMed1992

Developmental stages of the vomeronasal organ in the rat: a light and electron microscopic study.

This paper describes the development of the rat vomeronasal organ from the stage of anlage until adulthood. Groups of four rats were sacrificed daily from prenatal day 13 (E13) until birth; at days 2, 4, 7, 10, 14 and 16 after birth; weekly from day P21 to P42 plus an additional group of adults. The vomeronasal organs were processed for light microscopy, including alcian blue-PAS and NADH-diaphorase reactions, and also for electron microscopy. For summarizing our results we propose the following developmental stages: 1. Anlage (E13). 2. Early morphogenesis (E14-16). 3. Late morphogenesis (E17 to birth). 4. Initiation of secretory activity (First postnatal week). 5. Cytoarchitectural maturity (2nd postnatal week). 6. Complete maturity (From 3rd postnatal week onwards). Our results on the maturation of the histological structure and the histochemical reactions, indicate that there may be some functional activity at birth but the development of the organ still continues during the first three postnatal weeks to acquire its full functional capability.

Animals↗

PubMed1990

Postnatal development of striatal connections in the rat: a transport study with wheat germ agglutinin-horseradish peroxidase.

This paper deals with the postnatal development of afferent and efferent connections of the rat striatum as revealed by the transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP). Tracer was injected weekly from birth to the end of the first postnatal month in the head of the caudate nucleus. To control for transport from cortical areas contaminated by the micropipette, injections in newborn rats were made by either vertical or lateral penetrations. In addition some newborn and 14-day-old animals were injected only in the cortex. The results showed that at birth there was retrograde transport to the thalamus, substantia nigra and raphe nuclei. Labelling in the cortex was seen at birth but was probably due to cortical contamination. Transport from the striatum was clearly established on day 7, when a few labelled neurons were observed on both the ipsi and contralateral sides. These neurons increased in number and were distributed through layers III to VI by day 14. At this time labelled cell bodies were observed in the claustrum and lateral amygdaloid nucleus as well as in the globus pallidus and entopeduncular nucleus. On day 21 the contralateral labelling of the lateral amygdaloid nucleus was apparent. The anterograde transport from the striatum to globus pallidus, entopeduncular nucleus and substantia nigra was already visible at birth although its intensity increased during the first postnatal month.

Aging↗

PubMed1990

Alterations in prolactin secretion during the 1st postnatal month following perinatal dopaminergic blockade with haloperidol.

This research was intended to study the effects of perinatal haloperidol administration on the postnatal secretion of prolactin (PRL) with the aim of investigating the existence of a 'critical period' during which the lack of dopamine influence could cause long-term alterations in the secretion of this hormone. A first group of animals, composed of pregnant rats, was injected daily with haloperidol (1 mg/kg) from day 16 of gestation to delivery. A second group of newborn rats received the same dose from days 2 to 6 after birth. Pituitary and serum PRL were measured weekly by radioimmunoassay during the 1st postnatal month in pups from the injected mothers, in postnatally injected rats, and in controls. The results showed a significant increase in the pituitary amounts of PRL that was more intense after the prenatal treatment, especially in the females. In serum, the prenatal treatment induced PRL levels higher than in the controls, whereas the postnatally injected group exhibited a V-shaped response which has been described as characteristic of neuroleptic withdrawal. These data confirm the existence of a 'critical period' during which perinatal administration of haloperidol alters the postnatal PRL production and secretion patterns. The persistence of high PRL contents in pituitary may reflect an alteration in the hormone synthesis and/or an increase in the rate of somatomammotrophes that differentiate into lactotrophes after suppression of dopamine influence. The high PRL levels in serum indicate a failure in the control of PRL release, perhaps after damaging the tuberoinfundibular neurons as a consequence of the high prolactinemia induced by the treatment.

Animals↗

PubMed1988

Long-term ototoxic effects of neomycin applied topically in the middle ear: a morphological study in the guinea pig.

Neomycin was instilled daily, uni- or bilaterally, into the middle ear of guinea pigs for three months. The cochleae were examined, by light and electron microscopy, six months after the end of treatment. The organs of Corti of the treated ears were completely destroyed, and in the most advanced lesions, were substituted by a single layer of very thin flat cells. In the spiral ganglion only some glial cells and a few neurons could be observed. All surviving neurons were myelinated, and their ultrastructure was greatly altered, with disorganization of the rough endoplasmic reticulum and ribosomes. The basilar membrane almost disappeared, losing it amorphous and filamentous components. The spiral limbus and the stria vascularis were atrophic and were also covered, in the final stages, by flat elongated cells. In view of its morphological characteristics, this epithelium may arise from the displacement of the interdental cells and perhaps from the cochlear surface of Reissner's membrane.

Administration, Topical↗

PubMed1988

Growth of two types of cartilage after implantation of free autogeneic perichondrial grafts.

The perichondrium of adult rats was dissected from the posterior side of the ear where a plane of separation can be easily found between the superficial chondrocytes and the rest of the cartilage. When pulled off, the perichondrium brings with it a cartilaginous strip adhered to its inner layer, with the detachment surface showing projections of broken capsular matrix (PBCM). The perichondrium and subperichondrial cartilage were then transferred as autogeneic grafts to preformed muscle pockets of the abdominal wall and to everted vein chambers placed free in the iliac blood flow. During a period of one to 12 days, chondrogenesis was studied in the grafts and in the graft bed areas next to subperichondrial cartilage. When the perichondrium was placed into a muscular pouch, wherein perichondrocytes survived and a prominent vascular ingrowth in the graft bed was observed, the presence of two types of newly formed cartilage was demonstrated (Types I and II). These types showed differences in their location, time of appearance, and microscopic characteristics. Type I neocartilage appeared in the inner layer of the perichondrium on the third or fourth day after grafting; at this time the cells, surrounded by a well-defined capsular matrix, were large, darkly stained, and highly electron dense. Type II neocartilage, separated from Type I by the PBCM, appeared in the graft bed area located within perichondrial folds on the sixth or seventh day after implantation. Their cells showed a poorly defined capsular matrix and were smaller, lighter stained, and less electron dense than those of Type I. When the perichondrium was transplanted to everted vein chambers placed in the iliac blood flow, wherein perichondrocytes survived and vascular ingrowth from the graft bed was not present, Type I neocartilage was formed but Type II was not. The morphologic and histoautoradiographic findings in these studies suggest that Type I cells come from perichondrocytes of the inner perichondrial layer, whereas Type II cells originate from the undifferentiated perivascular mesenchymal cells of the graft bed.

Animals↗

PubMed1985

The trigemino-olivary projection in the cat: contributions of individual subnuclei.

Anterograde autoradiographic methods were used to determine the projection of the principal sensory trigeminal nucleus and of each of the three spinal trigeminal subnuclei to the inferior olivary complex in the cat. Our data reveal that the principal sensory trigeminal nucleus does not contribute to the trigemino-olivary pathway. Each spinal trigeminal subnucleus has a unique contribution to this pathway: pars oralis projects sparsely to the border between the dorsal accessory and principal olives (DAO-PO), pars interpolaris projects mostly to the rostral medial DAO, and pars caudalis projects mostly to the rostral medial part of the ventral leaf of PO and slightly to the caudal medial accessory olive. In the light of recent physiological and anatomical findings, our data indicate that information from each spinal trigeminal subnucleus reaches a different segment of the contralateral inferior olivary complex, which in turn distributes differentially to the cerebellar cortex.

Animals↗

PubMed1985

A versatile and simple method for staining nervous tissue using Giemsa dye.

A method for staining nervous tissue with Giemsa dye is described. The procedure is easy to perform and works well on paraffin, celloidin and frozen sections. The results combine the properties of the Nissl stains with the polychromatism of the Romanowsky dyes. The method also provides good results for counterstaining autoradiographies, or when applied after horseradish or peroxidase-antiperoxidase techniques. In the latter case, Giemsa dye darkens the immunoreactive product in the same manner as osmium tetroxide but avoids the well-known risks of handling this toxic agent.

Animals↗

PubMed1983

Afferent pathways to points of self-stimulation in the medial prefrontal cortex of the rat as revealed by the horseradish peroxidase technique.

Afferent projections to points of self-stimulation (SS) in the medial prefrontal cortex (MPC) of the rat were studied using the horseradish peroxidase (HRP) technique. Intracranial microinjections of HRP (30%) were delivered at the same stereotaxic points at which the electrodes eliciting SS were located. Retrogradely transported HRP labeled neurons in different thalamic, hypothalamic, mesencephalic and pontine areas. In the thalamus, labeled neurons were found in the dorsomedial, anteromedial, anteroventral, ventral, ventromedial, posteromedial, paratenial, parafascicular nuclei and n. reuniens. Labeled neurons in mesencephalic areas were found in the n. interpeduncularis, ventral tegmental area (AVT) and substantia nigra (SN). In the pons, labeled neurons were found in the locus coeruleus and in the periaqueductal gray. Other nuclei in which labeled neurons were also found were: lateral hypothalamus (LH), periventricular gray and zona incerta (ZI). Theoretically it is possible that all these afferent areas contribute to SS of MPC. This assumption is discussed and criticized in connection with previous literature on SS. It is suggested that only specific areas and their projections are good candidates for the neural mechanisms involved in the reward produced by electrical stimulation of the prefrontal cortex.

Afferent Pathways↗