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A K Shetty

Publications and source records attributed to A K Shetty.

At least 91 records · Page 5Linked to original sources
PubMed1995

Enhanced cell survival in fetal hippocampal suspension transplants grafted to adult rat hippocampus following kainate lesions: a three-dimensional graft reconstruction study.

The success of fetal neural transplantation in alleviating neurological dysfunction depends significantly on the degree of graft cellular survival and dispersion within the host. We hypothesize that various lesion-induced host factors, such as trophic support and denervation, enhance these graft factors differentially following unilateral intracerebroventricular kainic acid lesions. We have performed quantitative graft reconstructions of embryonic day 19 fetal hippocampal cells transplanted at different post-lesion delays (four, 11, 26 and 60 days) into adult hippocampus. We have used a permanent graft prelabel (5'-bromodeoxyuridine) which allows unambiguous identification of graft cell location in the host. Cellular integration of grafted cells was rigorously assessed by calculating both absolute cell survival (cells recovered/cells injected) and quantitative cell dispersion from the graft injection site. Graft cell survival and graft volume were dramatically enhanced in transplants performed ipsilateral to the kainic acid lesion, to a maximum of 77% cell recovery at a post-lesion graft delay of four days. Cell survival decreased over time after the lesion to the level of the contralateral grafts by 60 days post-lesion (33% cell survival), though cell survival on either side remained significantly greater than grafts into normal hosts (18% survival). The time-course of post-lesion enhanced survival (four to 26 days) in hippocampus ipsilateral to the lesion strongly correlated with reported peak neurotrophic activity (four to 30 days). Graft cell dispersion was limited in this model, averaging less than 500-microns-cell movement; there were no differences compared to transplants grafted into normal hippocampus. Timm's staining demonstrated host mossy fiber innervation of transplants to be denser ipsilateral to the kainic acid lesion, resulting in a partial decrease in dentate supragranular sprouting near appropriate grafts placed at early post-lesion time points. These results suggest that lesion-induced trophic support and denervation lead to improved graft cell survival but not graft cell dispersion. The improved survival of grafts transplanted into hippocampus contralateral to the lesion, compared to transplants in normal hippocampus, suggests that denervation alone exerts a significant effect on graft cell survival. However, this denervation effect on graft cell survival is significantly less than the combination of both enhanced neurotrophic factors and denervation observed ipsilateral to the lesion.

Animals↗
PubMed1995

Selective laser-activated lesioning of prelabeled fetal hippocampal grafts by intracellular photolytic chromophore.

Selective removal of grafted tissue is critical to assess the functional role of that tissue in the host, yet is technically difficult for well-dispersed neural grafts. We labeled fetal hippocampal cells with both a nuclear marker (5'-bromodeoxyuridine) and a cytoplasmic marker (latex microspheres) before grafting into normal adult hippocampus. A nontoxic chromophore, chlorin e6, was conjugated on to the surface of latex microspheres of the treatment group. Chlorin e6 produces cytotoxic singlet oxygen only during photoactivation. Grafted animals received transcranial exposure to various intensities of near-infrared laser light. Following laser exposure, grafts were observed in all groups except in transplants prelabeled with chlorin e6 latex microspheres. An optimal laser exposure of 50-100 J/cm2 (4-8 min) was found to selectively remove only the chlorin e6-containing grafted cells. With increasing doses of laser illumination, non-specific lesions of the host tissue surrounding the graft were induced. Quantitative graft analysis, in the absence of laser exposure, indicated that the survival of grafted cells was similar between control transplants labeled with latex microspheres alone and grafts labeled with latex microspheres plus chlorin e6. This is further evidence that chlorin e6 by itself was not toxic without laser exposure. The results clearly demonstrate that singlet oxygen-induced cell photolysis can result in selective, non-invasive removal of dispersed grafted cells located in adult hippocampus. This technique may facilitate defining specific mechanisms of action of grafted cells which mediate functional recovery in different host conditions.

Animals↗
PubMed1994

Reactive astrocytes express the embryonic intermediate neurofilament nestin.

Nestin is a neurofilament protein expressed by the immediate precursors to neurons and glia in rats and humans. Nestin immunoreactivity in the rat CNS was studied following kainic acid (KA) hippocampal lesions. Numerous nestin positive cells within the KA lesion were confirmed to be reactive astrocytes by their immunoreactivity for glial fibrillary acidic protein (GFAP). The number of these cells decreased with time after the KA lesion and no astrocyte immunostaining for nestin was observed in control animals. A subset of nestin-positive cells in the ventricular subependymal region appeared to be radial glial cells, extending to cell body layers. Nestin is one of several embryonic markers expressed by reactive astrocytes, suggesting an embryonic reversion induced by the KA lesion, possibly to enhance functional recovery.

Animals↗
PubMed1994

Quantitative graft integration of fetal hippocampal transplants labeled with 5' bromodeoxyuridine into normal adult hippocampus.

Quantitative studies of neural graft development require: (1) a cell label which is both preferential for neurons and can be measured in terms of specific labeling; (2) a serial reconstruction method for identifying labeled cells in a three-dimensional pattern in the host; and (3) measurements of cell dispersion which indicate the specificity of cell movement in the host. We have used 5' bromodeoxyuridine (BrdU) as a nuclear marker of transplanted fetal hippocampal cells, performing daily injections into the donor to label the majority of cells in the hippocampus between Gestation Days 15 and 19. After harvesting, the BrdU-labeled hippocampal cell suspensions were either cultured or grafted into normal adult hippocampus. The labeling index of these fetal hippocampal cells was calculated to be 90% in both smears of cell suspensions and 48-h cultures and these were predominantly (77%) neurons by immunostains. Quantitative studies of potential toxicity of the BrdU in culture also revealed no differences in neurite development or survival, compared to unlabeled cells. The survival and migration of grafted cells were quantitatively evaluated by three-dimensional serial reconstruction of host brain sections. Absolute graft cell survival (cells recovered/cells injected) varied according to location: grafts in close proximity to the ventricle and white matter tracts (corpus callosum or fimbria) showed improved survival (20 and 25%, respectively) compared to grafts localized entirely within the (normal) hippocampus (only 9% survival). Although the grafts expanded considerably from the initial injection site, the graft cell dispersion appeared nonspecific. Thus, this format of quantitative graft assessment indicates that under normal (nonlesioned) host conditions the location of the grafts critically influenced graft development and there was minimal specific migration of grafted cells into cell body regions.

Animals↗
PubMed1994

Combined pre- and postnatal ethanol exposure alters the development of Bergmann glia in rat cerebellum.

The development and maturation of Bergmann glial cells in the rat cerebellum was evaluated on postnatal day 15 by glial fibrillary acidic protein (GFAP) immunocytochemistry, following combined gestational and 10-day postnatal ethanol exposure (a full three trimester human equivalency). GFAP-positive Bergmann glial fibers of lobules I, III, VIb, VII and X of the cerebellar vermis were examined and counted in the molecular layer (ML), the external granular layer (EGL) and the external limiting membrane (ELM). Ethanol exposure reduced: (1) the number of GFAP-positive fibers (per unit length of folia surface) at all three levels; (2) the percentage of mature fibers; and (3) the cross-sectional area in all lobules examined. When data from the five lobules were pooled, there were 7% fewer GFAP-positive fibers in the ML, 15% fewer in the EGL and 20% fewer in the ELM; the percentage of mature fibers was reduced by 16%; and the cross-sectional areas of lobules were reduced by 16%. The altered development of Bergmann glia could be one of the factors causing delayed migration of granular neurons and reductions in the number of granule cells reported in other studies following developmental ethanol exposures and could help to explain some of the motor dysfunctions reported in FAS victims.

Alcohol Drinking↗
PubMed1993

Alterations in neuronal development in the substantia nigra pars compacta following in utero ethanol exposure: immunohistochemical and Golgi studies.

The effects of gestational ethanol exposure on the development of dopaminergic neurons of substantia nigra pars compacta were investigated in the rat. Pregnant rats were either fed an ethanol-containing liquid diet (6.7% v/v) or pair-fed an isocaloric diet throughout gestation. The morphology of neurons in both ethanol-exposed and pair-fed control offspring was assessed on postnatal day 15 by using tyrosine hydroxylase immunohistochemistry and Golgi impregnation methods. Alterations in the development of neurons were indicated in ethanol-exposed offspring compared with control offspring by the following: (i) tyrosine hydroxylase-positive cell bodies were smaller and appeared more closely packed; (ii) the numbers of second-, third- and fourth-order dendrites and total dendritic segments per cell were reduced; (iii) the dendritic branching pattern relative to distance from the soma was altered; and (iv) some dysmorphic neurons with irregular cell body contours and spheroidal enlargements in the dendrites were encountered in both tyrosine hydroxylase-immunostained and Golgi-stained specimens. The results of the present study suggest that gestational ethanol exposure causes retardation in the development of substantia nigra pars compacta neurons, especially in their dendritic growth and branching, and also causes pathological changes in some neurons. The underdevelopment of dendrites could result in altered development of neuronal circuitry which, in turn, could result in abnormal motor function.

Animals↗
PubMed1992

Effects of prenatal ethanol exposure on the development of Bergmann glia and astrocytes in the rat cerebellum: an immunohistochemical study.

The consequences of prenatal ethanol exposure on the postnatal development of Bergmann glia and astrocytes in the rat cerebellum were investigated by using glial fibrillary acidic protein (GFAP) immunolabeling. Pregnant rats were either fed with an ethanol containing liquid diet (6.7% v/v) or pair-fed with an isocaloric diet throughout gestation. On postnatal day (PD) 15 and 22, parasagittal sections of the cerebellar vermis from female offspring were processed for GFAP immunohistochemistry to assess the development of Bergmann glia and astrocytes in lobules I, VII, and X and astrocytes in the central core of white matter. On PD 15, compared to control animals, ethanol exposed animals had fewer GFAP positive Bergmann glial fibers per unit length of molecular layer; a significantly greater percentage of morphologically immature Bergmann fibers; a significantly greater GFAP positive astrocytic area per unit area of internal granular layer and central white matter; and the astrocytic processes were wider and more closely packed. These glial changes were associated with significantly thicker external granular layer in all 3 lobules. However, no significant differences were seen between the ethanol exposed and control animals on PD 22, indicating "catch-up growth" in the ethanol exposed animals during the third postnatal week. These results suggest that prenatal ethanol exposure causes (1) delayed maturation of Bergmann glia, which in turn contributes to the delayed migration of granule cells; and (2) alterations in the normal postnatal development of astrocytes.

Animals↗
PubMed1991

Fetal nigral grafts in the anterior eye chamber of adult rats: a long-term morphological study.

Substantia nigral grafts of 16 and 17 gestation days showed phenotypic characteristics in the anterior eye chamber of adult rats until the third month after transplantation. Thereafter by the sixth month a number of neurons showed somal and dendritic thickening, reduced population of endoplasmic reticulum, increase in lysosomes, and clear areas devoid of organelles, indicating age changes. These changes were progressive and affected more neurons by the end of 1 year, the longest period studied. The observations suggest that the maturation of nigral neurons is independent of specific afferent input, whereas target influence is necessary for the continued maintenance of the mature neurons. All the synapses observed in the transplant were of the asymmetric variety, reminiscent of the few intrinsic synapses of the intact nigra. This suggested establishment of mutual connectivity among the transplanted neurons in the absence of a target and the type of synapse formed may have been influenced by the local environment. Large glial processes, very prominant during the 4- to 6-month period became less significant afterward but continued to be present until the end of the period studied. Though there was no morphological evidence of lymphocytic infiltration, this might suggest an immunologic reaction.

Aging↗
PubMed1991

Ageing changes in the transplants of fetal substantia nigra grafted to striatum of adult rat.

Fetal nigral neurons from 16 and 17 gestational days were transplanted into the intact striatum of adult rat. On different post-transplantation days (30-360 days), the structural and immunohistochemical details of the transplants were studied. The grafted neurons matured and showed phenotypical characteristics comparable to that of normal nigral neurons in adult rats until 180 days. Tyrosine hydroxylase-positive neurons were seen not only in the transplant but also in the adjacent host striatum. Tyrosine hydroxylase-positive fibres were also seen extending for a short distance into the host striatum. A large number of synapses in the transplants were of asymmetric type, containing clear round vesicles. These synapses resembled the few intrinsic type present in the normal substantia nigra. On the other hand, the predominant type 2 synapses with pleomorphic vesicles in the normal nigra were infrequently encountered in the transplants. On the 300th day, the cytoplasm of a few of the neurons showed ageing changes in the form of clear spaces, paucity of organelles especially rough endoplasmic reticulum, membrane-bound vacuoles and increase in the lipofuscin population. In addition, localized thickening of the soma and the dendrites were seen in relation to randomly distributed neurons. By 360 days, more than one quarter (26%) of the total neurons showed these changes indicating ageing. The number per unit volume of normal neurons decreased significantly when compared to the transplants on 60 and 90 days. In the substantia nigra of age-matched control, except for an increase in the lysosomal population, other ageing changes were not detectable. The neurons of intact substantia nigra of the host rat, chronologically 4-8 months older than the transplanted neurons, also appeared normal but for lipofuscin granules. The present study provides morphological evidence for rapid ageing of neurons in the long term nigral transplants. These observations raise fresh doubts regarding permanent survival of grafted neurons in the host brain. Studies so far conducted are after prior nigral lesions. Trophic factors following lesions of the host tissue may have influenced the long term survival of the transplanted neurons. On the other hand, such changes may have been missed since no detailed morphological investigations of the long term transplants have been done so far.

Aging↗
PubMed1991

Adrenal medullary autografts in anterior eye chamber, lateral ventricle and striatum of adult rats: a long term study.

The neurobiological basis for the short-term recovery in Parkinson's patients and experimental animals grafted with adrenal medulla is not yet clear. Structural details of the grafted chromaffin cells are also not available. In the present study, autografts of adrenal medulla in the anterior eye chamber, lateral ventricle and striatum of adult rats were studied for 360 days. Though a large number of cells degenerated, a few healthy chromaffin cells survived up to 360 days in the anterior eye chamber. In the ventricular and striatal regions, cells degenerated more rapidly, and a few surviving cells were seen only up to 120 and 150 days, respectively. Degeneration of the cells was evident from the alteration of the cytoplasmic granules, appearance of vacuoles and lysosomes, rapid decline in the number of TH and DBH positive cells and diffusion of enzymes in the intercellular region. Only lymphocytes and connective tissue cells were seen in the ventricle after 120 days, while outlines of a few chromaffin cells and background fluorescence were still evident in the striatum up to 150 days. In some of the intrastriatal transplants, morphologically identifiable Schwann cells were present and, in one transplant, there was evidence of myelination of axons by Schwann cells. These axons were obviously derived from the adjacent host tissue. From the findings it has been concluded that autografts of adrenal medulla survive for only a limited period of time on transplantation to the central nervous system and anterior eye chamber. Survival seemed to be better in the anterior eye chamber than at the sites preferentially chosen for treating Parkinson's patients or experimental animals.

Adrenal Medulla↗
PubMed1991

Fetal nigral transplants in the lateral ventricle of adult rats. A long-term morphological study.

The substantia nigra from rats of 16 and 17 gestational days grafted into the lateral ventricle of adult rats grew into isolated or partially integrated transplants in 80% of the rats. The morphological details of the transplants were studied at intervals of 30-360 days. The neurons grew, differentiated and were comparable to age-matched controls until 150 days. Thereafter, the neurons showed progressive aging changes like dendritic thickening, clear spaces, membrane-bound vacuoles and increase in lysosomes in the cytoplasm. The numerical density per unit volume (Nv) of normal neurons significantly decreased with simultaneous increase in Nv of glial cells by 360 days. These changes were slower to develop in the partially integrated transplants: it is concluded that target tissue interaction is necessary for prolonged survival of the grafted tissue.

Aging↗
PubMed1984

Computed tomography of spine trauma.

Nine patients admitted to the hospital for spine trauma were studied with computed tomography. The use of computed tomography minimized patient motion, allowed excellent definition of compromise of the spinal canal by fracture fragments, and better delineated fractures of the neural arches than plain films or tomography. Plain radiographs and computed tomography scans permitted complete evaluation of spine trauma with no additional investigations being necessary.

Adult↗
PubMedDate not supplied

Systemic lupus erythematosus and sickle cell disease.

A case of 10-year-old girl with an unusual association of sickle cell disease (SCD) with systemic lupus erythematosus (SLE) is presented. The report discusses the clues to the diagnosis of this rare combination with review of relevant literature and highlights the diagnostic dilemma that may arise because of the similarity of symptoms.

Anemia, Sickle Cell↗
PubMedDate not supplied

Proximal femoral focal deficiency (PFFD).

A 1-year-old child with proximal femoral focal deficiency (PFFD) is presented. The clinical spectrum and associated abnormalities is described and the diagnosis and management of this entity is discussed.

Acetabulum↗
PubMedDate not supplied

Sickle cell anemia with systemic lupus erythematosus: response to hydroxyurea therapy.

PURPOSE: To report the efficacy of hydroxyurea (HU) in a patient with sickle cell anemia (SCA) associated with systemic lupus erythematosus (SLE). PATIENTS AND METHODS: An unusual association of SCA with SLE occurred in a 14-year-old black girl. Her medical history was significant for repeated vasoocclusive crises requiring repeated hospitalizations and transfusions, acute chest syndrome, hyperhemolytic crises, multiple transfusions resulting in iron overload, gall stones, avascular necrosis, and significant psychosocial problems. Her lupus activity was controlled with oral prednisone and hydroxychloroquine. Treatment with oral HU was instituted at an initial dose of 20 mg/kg with gradual increment to a maximum of 25 mg/kg daily. RESULTS: A dramatic clinical improvement was noted with HU therapy with no episode of pain crisis or hospitalization for 5 months. There was an increase in fetal hemoglobin (HbF) to 20.9% and mean corpuscular volume to 114.5 fl, but her Hb level remained steady at 7.5 g/dl. No toxicity was noted with HU therapy. In addition, a significant change was also observed in her school performance, social activities, and general quality of life. CONCLUSIONS: HU therapy may be beneficial and safe and should be considered for other patients who have SCA with SLE.

Adolescent↗