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D A Peterson

Publications and source records attributed to D A Peterson.

At least 19 recordsLinked to original sources
PubMed1996

Differentiation of adult hippocampus-derived progenitors into olfactory neurons in vivo.

Neurogenesis continues throughout adulthood in discrete regions. Proliferative zones include the subependymal zone, from where progenitors migrate along the rostral migratory pathway to differentiate into neurons in the olfactory bulb, and the hippocampal subgranular zone, where they migrate and differentiate into granule neurons. Progenitors isolated from adult subependymal zone exhibit in vitro neurogenesis when stimulated with epidermal or fibroblast growth factor. Cultured adult rat hippocampal progenitors (AHPs) grafted to adult rat hippocampus show site-specific neuronal differentiation. Here we investigate determinants of multipotentiality in the adult central nervous system, by grafting AHPs into homotypic (hippocampus) or heterotypic (the rostral migratory pathway) neurogenic sites or a heterotypic, non-neurogenic site (the cerebellum). We found that grafts into neurogenic, but not nonneurogenic sites, showed neuronal differentiation. Furthermore, AHPs grafted in the rostral migratory pathway migrated into the olfactory bulb, differentiating into tyrosine-hydroxylase-positive neurons, a non-hippocampus phenotype. These results reveal that AHP populations can respond to persistent neuronal differentiation cues in the adult central nervous system.

Adult↗
PubMed1996

Sprouting adult CNS cholinergic axons express NILE and associate with astrocytic surfaces expressing neural cell adhesion molecule.

To assess the cellular and molecular substrates for cholinergic axon growth in the adult central nervous system (CNS), we implanted grafts of control and nerve growth factor (NGF)-producing genetically modified fibroblasts within the striatum of rats. Sprouting cholinergic axonal processes that grew into grafts of NGF-producing fibroblasts were fasciculated and followed the surface of astrocytic processes for long distances within the grafts. The close and long distance anatomical relationship between the sprouted axons and the astrocytes supported previous ultrastructural evidence that astrocytes may serve as a cellular substrate for sprouting cholinergic axons in vivo. The sprouted axon processes were associated with the expression of nerve growth factor-inducible large external (NILE) glycoprotein on their surfaces. NILE expression was not seen in control grafts where there was an absence of cholinergic ingrowth. NILE has been demonstrated to play a role in axon fasciculation in a number of other neural systems. The astrocytic processes in both control and NGF-producing fibroblast grafts expressed neural cell adhesion molecule (NCAM), suggesting that NCAM-mediated adhesion may be responsible for the close relationship between the axons and astrocytes within the grafts. NGF-induced heterotypic interactions between neuronal NILE and astroglial NCAM may also be required for adult cholinergic axonal sprouting.

Acetylcholine↗
PubMed1996

Fibroblast growth factor-2 protects entorhinal layer II glutamatergic neurons from axotomy-induced death.

The entorhinal cortex is a major relay between the hippocampus and other cortical and subcortical regions. Glutamatergic axons from layer II neurons form the entorhinal cortical projection to the hippocampus via the perforant pathway. We have demonstrated previously that lesion of the perforant pathway causes the death of approximately 30% of entorhinal layer II (ECL2) neurons. To elucidate mechanisms contributing to neuronal death and to investigate strategies preventing it, we identified the phenotype of the vulnerable neuronal population. Sections were immunolabeled with antibodies to the neuronal markers NeuN, glutamate, and calbindin-D28k, and to receptors for fibroblast growth factor-2 (FGFR1) and NMDA (NMDAR1) and were examined using confocal microscopy. Calbindin immunoreactivity was strikingly lamina-specific to ECL2, where one-third of all ECL2 neurons were calbindin-positive. Localization of glutamate revealed that half of the glutamatergic ECL2 neurons coexpressed calbindin. Quantification using unbiased stereology at 9 weeks after lesion of the perforant pathway revealed that the only ECL2 neuronal population that experienced a significant (70%) loss (20% of the total) was the population of glutamatergic ECL2 neurons that did not coexpress calbindin. All ECL2 neurons expressed FGFR1; therefore, we tested the role of FGF-2 in the survival of glutamatergic ECL2 neurons. We grafted fibroblasts genetically engineered to express nerve growth factor or FGF-2 and found that only FGF-2 grafts prevented loss of the vulnerable glutamatergic/calbindin-negative neurons. We present a hypothesis for the selective vulnerability of these glutamatergic/calbindin-negative ECL2 neurons and address the role of FGF-2 in neuronal rescue.

Afferent Pathways↗
PubMed1996

Improved resolution of fibronectin mRNA expression in the inner ear using laser scanning confocal microscopy.

We describe a modified in situ hybridization protocol for localizing and quantifying fibronectin gene expression at the cellular level in paraffin sections of rat temporal bone. When combined with a novel analytical approach using laser scanning confocal microscopy (LSCM), this protocol significantly improved the resolution, sensitivity, and specificity of existing procedures for evaluating fibronectin synthesis in developing inner ear. For simultaneous viewing of cochlear anatomy and the autoradiographic signal, transmitted light images of the cochlea were collected separately from LSCM reflected light images of the autoradiographic silver grains and then the two images were electronically merged. Within the first 2 microns below the surface of the emulsion, silver grains were clustered specifically over hybridized cells. In contrast, nonspecific silver grain development (i.e., background noise) was confined primarily to the lower 5 microns of the emulsion adjacent to the tissue section. Limiting the volume of the emulsion examined in the LSCM analysis, i.e., restricting the range of optical sectioning to the first 2 micron below the surface of the emulsion, effectively minimized nonspecific background noise and maximized the specificity of the hybridization signal. The improvements offered by the described methodological approaches are equally appropriate for non-calcified tissues.

Animals↗
PubMed1995

Survival and differentiation of adult neuronal progenitor cells transplanted to the adult brain.

The dentate gyrus of the hippocampus is one of the few areas of the adult brain that undergoes neurogenesis. In the present study, cells capable of proliferation and neurogenesis were isolated and cultured from the adult rat hippocampus. In defined medium containing basic fibroblast growth factor (FGF-2), cells can survive, proliferate, and express neuronal and glial markers. Cells have been maintained in culture for 1 year through multiple passages. These cultured adult cells were labeled in vitro with bromodeoxyuridine and adenovirus expressing beta-galactosidase and were transplanted to the adult rat hippocampus. Surviving cells were evident through 3 months postimplantation with no evidence of tumor formation. Within 2 months postgrafting, labeled cells were found in the dentate gyrus, where they differentiated into neurons only in the intact region of the granule cell layer. Our results indicate that FGF-2 responsive progenitors can be isolated from the adult hippocampus and that these cells retain the capacity to generate mature neurons when grafted into the adult rat brain.

Animals↗
PubMed1995

Opposing effects of oxidants and antioxidants on K+ channel activity and tone in rat vascular tissue.

K+ channels regulate tone in both the systemic and pulmonary circulations. K+ channel inhibition leads to membrane depolarization, Ca2+ influx and vasoconstriction; K+ channel activation leads to hyperpolarization and vasodilatation. The sulfhydryl oxidant diamide opens K+ channels in pulmonary smooth muscle and acts as a potent vasodilator in perfused lungs. We examined the hypothesis that antioxidants cause constriction and oxidants cause relaxation through their effects on K+ channels in vascular smooth muscle. The oxidant diamide (380 microM and 3.8 mM) inhibited the reduction of cytochrome C by ferrous sulphate in vitro whilst the antioxidants co-enzyme Q10 (770 microM) and duroquinone (700 microM) increased the rate of reduction. Both antioxidants caused dose-dependent constriction of endothelium-intact and -denuded rat pulmonary artery and aortic rings. This constriction could be reversed by 1 microM diamide. Co-enzyme Q10 and duroquinone (both at 100 microM) partially inhibited (approximately 30%) whole-cell K+ channel currents and depolarized membranes of isolated pulmonary artery smooth muscle cell recorded using the amphotericin-perforated-patch-clamp technique. Diamide (100 microM) increased whole-cell K+ channel currents and hyperpolarized the membrane. The data suggest that oxidants and antioxidants may modulate vascular tone via an effect on K+ channels.

Animals↗
PubMed1995

Dithionite increases radical formation and decreases vasoconstriction in the lung. Evidence that dithionite does not mimic alveolar hypoxia.

Dithionite is a powerful reducing agent used to deoxygenate hemoglobin and create anaerobic conditions in vitro. Recently, dithionite has been used as a convenient means of creating "hypoxia" in experiments studying the O2 sensor in the pulmonary circulation and carotid body. We evaluated the hypothesis that hypoxia created by hypoxic ventilation and that created by dithionite have different effects on the pulmonary circulation. In vitro, dithionite (10(-5) to 10(-3) mol/L), added to oxygenated Krebs' solution, rapidly created superoxide anion in a dose-dependent manner. Dithionite consumed O2 in parallel with the generation of superoxide radical, with both processes peaking within seconds. Anoxia was sustained only if resupply of O2 was prevented. In isolated rat lungs (whether perfused with autologous blood or Krebs' solution), hypoxic ventilation alone lowered perfusate PO2 from approximately 140 to 40 mm Hg and decreased lung levels of activated oxygen species (AOS), measured by luminol-enhanced chemiluminescence, before the onset of hypoxic pulmonary vasoconstriction. Constrictor responses to angiotensin II and KCl were not impaired by intermittent hypoxic challenges, and lung weight did not increase. In contrast, dithionite impaired constrictor responses of the Krebs' solution-perfused lungs to all vasoconstrictors tested and increased lung weight. When given as a bolus (5 x 10(-3) mol/L) into the pulmonary artery during normoxic ventilation, dithionite caused no vasoconstriction and only briefly lowered PO2 (because of constant resupply of O2 from the alveoli). When superimposed on hypoxic ventilation, dithionite further lowered PO2 from approximately 40 to approximately 0 mm Hg and caused additional constriction. Unlike hypoxic ventilation, dithionite increased AOS production. Antioxidant enzymes diminished dithionite-induced radical production and diminished the loss of vascular reactivity and lung edema. In conclusion, unlike hypoxic ventilation, dithionite causes edema and loss of vascular reactivity in the lung by generating superoxide anion and hydrogen peroxide. Hypoxia elicited by dithionite is not equivalent to authentic hypoxia because of the obligatory associated generation of AOS. Dithionite usage should not be substituted for authentic hypoxia in studies of O2 sensing.

Animals↗
PubMed1995

The long accessory flexor muscle: an anatomical study.

A total of 136 lower limbs from 68 human cadavers were dissected to determine the incidence of the long accessory flexor muscle and its origins and insertions. The muscle was present in 11 of 136 lower extremities (8%) and 9 of 68 cadavers (13%). Five long accessory flexor muscles originated from the tibia and fascia of the deep posterior compartment and six began on the fibula. All of the tendons were deep to the laciniate ligament and coursed within the tarsal tunnel. All five of the tendons originating from the tibia inserted on the quadratus plantae, with two of the tendons having an additional insertion on the flexor digitorum longus. Three of the tendons with fibular origin inserted on the quadratus plantae and three inserted on the flexor digitorum longus. The importance of the long accessory flexor muscle relates as a cause or association with tarsal tunnel.

Aged↗
PubMed1995

Enhanced survival and neuronal differentiation of adrenal chromaffin cells cografted into the striatum with NGF-producing fibroblasts.

Although adrenal medullary chromaffin cells have been used extensively for intracerebral grafting, their survival has generally been poor. Improved survival of the implanted cells has been achieved by exposing the chromaffin cells to NGF in vivo. Culture studies have shown, however, that chromaffin cells are converted into sympathetic neurons when NGF is included in the medium. The degree to which such a transdifferentiation may occur in vivo has not been determined. We assessed the effects of cografting chromaffin cells with primary fibroblasts genetically engineered to express NGF. Chromaffin cells from 10 d old rats were implanted with NGF-producing or beta-galactosidase-producing primary fibroblasts (control fibroblasts) into the striatum of 6-hydroxydopamine treated adult rats of the same strain. Eight weeks postgrafting, chromaffin cells cografted with NGF-producing fibroblasts displayed many of the features of mature sympathetic neurons such as large somata, long processes, transmitter vesicles similar to those found in neurons, and positive immunolabeling for the neuronal markers neurofilament, MAP2 and SCG10. Chromaffin-derived neuron number was also significantly enhanced in the presence of NGF-producing fibroblasts. While control fibroblasts were also found to increase chromaffin cell number above that of chromaffin cells grafted alone, the control fibroblasts did not induce neuronal transdifferentiation. These results demonstrate that chromaffin cells cografted with NGF-producing fibroblasts undergo transdifferentiation in vivo and express many characteristics of mature sympathetic neurons. The consequences of this transdifferentiation on the long term survival and function of the transplanted cells in vivo remain to be clarified.

Adrenal Glands↗
PubMed1994

Superoxide reduction of a disulfide: a model of intracellular redox modulation?

Superoxide dismutase (SOD), which breaks down superoxide to oxygen and hydrogen peroxide, is generally considered an antioxidant enzyme. However, superoxide is a potent reducing agent and as such could affect cellular function by reducing disulfides in important proteins, such as, ionic channels and pumps. In support of this concept, we show that superoxide, generated by two different sources, is able to reduce disulfide bonds in an in vitro model. Depending on the source of superoxide this reduction is accelerated by an unsaturated fatty acid or ferric iron and is inhibited by SOD.

Arachidonic Acid↗
PubMed1994

Fibroblasts genetically modified to produce nerve growth factor induce robust neuritic ingrowth after grafting to the spinal cord.

The influences of neurotrophic factors on adult mammalian spinal cords are incompletely understood. In the present experiment, we utilized somatic gene transfer to examine the effects of nerve growth factor (NGF) on the unlesioned spinal cords of adult Fischer rats. Fischer 344 rat primary fibroblasts were genetically modified in vitro to produce and secrete NGF, then grafted to spinal cords at the T7 level. Grafts survived in vivo for periods of up to 1 year, and induced an extremely robust ingrowth of spinal neurites. Control and basic fibroblast growth factor-producing grafts did not promote extensive neurite growth. Neurites penetrating the NGF grafts were of sensory origin, since they labeled immunocytochemically for calcitonin gene-related peptide but not markers of other neuronal transmitter phenotypes. Electron microscopy revealed that neurites within NGF-secreting grafts were enveloped in glial cell processes and that axons frequently became myelinated. These results indicate that (i) genetically modified cell grafts are a useful model for studying trophic factor effects in the adult mammalian spinal cord, (ii) sensory neurites maintain robust NGF responsiveness into adulthood, and (iii) sprouting neurites can follow glial channels and become myelinated in the adult spinal cord. Grafts of fibroblasts genetically modified to secrete trophic factors merit study as potential tools for promoting regeneration after spinal cord injury.

Animals↗
PubMed1994

Avascular necrosis of the first metatarsal head: incidence in distal osteotomy combined with lateral soft tissue release.

The incidence of avascular necrosis of the metatarsal head following distal first metatarsal osteotomy combined with adductor tendon release has not been documented in a large series of patients. Of 82 consecutive procedures in 64 patients performed between 1986 and 1988, 42 patients (58 procedures) were available for clinical and radiographic examination. Average follow-up was 2.5 years (range 1.0-4.2 years). There were 35 L-shaped and 23 chevron osteotomies which were combined with a lateral soft tissue release that included adductor tenotomy. Preoperative hallux valgus angle averaged 25 degrees (range 15-40 degrees), and intermetatarsal angle averaged 12 degrees (range 5-24 degrees). Follow-up amount of correction averaged 13 degrees and 5 degrees, respectively. Eighty-four percent of patients were satisfied with their result. There was one case of avascular necrosis. The patient was asymptomatic at 4.2 years' follow-up, and the remaining patients included two with infections, one hallux varus, and no nonunions.

Adult↗
PubMed1994

Perforant path damage results in progressive neuronal death and somal atrophy in layer II of entorhinal cortex and functional impairment with increasing postdamage age.

In vivo model systems that can evaluate neuronal death, survival, and regeneration are critical to revealing basic mechanisms of neuronal response and developing strategies for CNS repair. We propose a distinct experimental model of CNS degeneration following lesions to the perforant path connecting the hippocampus and the entorhinal cortex. Within 2 weeks of a unilateral aspirative perforant path lesion, 30% of the ipsilateral entorhinal cortex layer II (ECL II) projection neurons had died with no change in the contralateral ECL II population. Although there was no loss of ECL II neurons with normal aging, animals that survived for 15 months postlesion experienced an almost 50% loss of ipsilateral neurons compared to unlesioned controls. This progressive neuronal death was bilateral, with the contralateral ECL II experiencing a 30% decline in neuronal number relative to unlesioned controls. The use of unbiased stereology ensured that estimates of total number were not distorted by changes in the reference volume. The documented progressive neuronal death resulted in delayed behavioral impairment in spatial learning and performance (latency nearly 200% of controls). We propose, therefore, that the perforant path model is suitable for experimental investigation of neuronal survival and regeneration following CNS trauma.

Aging↗
PubMed1993

Proliferation, differentiation, and long-term culture of primary hippocampal neurons.

Primary embryonic hippocampal neurons can develop morphologically and functionally in culture but do not survive more than a few weeks. It has been reported that basic fibroblast growth factor (bFGF) promotes the survival of and neurite elongation from fetal hippocampal neurons. We report that bFGF, in a dose-dependent manner, can induce the survival (50 pg to 1 ng/ml) and proliferation (10-20 ng/ml) of embryonic hippocampal progenitor neurons in vitro. In serum-free medium containing high concentrations of bFGF, neurons not only proliferated (4-day doubling time) and differentiated morphologically but also could be passaged and grown as continuous cell lines. The neuronal nature of the proliferating cells was positively established by immunostaining with several different neuron-specific markers and by detailed ultrastructural analyses. The proliferative effect of bFGF was used to generate nearly pure neuronal cell cultures that can be passaged, frozen, thawed, and cultured again. Neurons have been maintained > 5 months in culture. The ability to establish long-term primary neuronal cultures offers the possibility that clonal lines of distinct neuronal cell types may be isolated from specific areas of the central nervous system. Such long-term neuronal cultures should prove valuable in studying neurons at the individual cell level and also in exploring interactions between neurons in vitro. The observed dose dependence raises the possibility that cell survival and proliferation in vivo may be influenced by different levels of bFGF.

Animals↗
PubMed1993

A structurally flexible and antigenically variable N-terminal domain of the hepatitis C virus E2/NS1 protein: implication for an escape from antibody.

Hepatitis C virus persists in most infected hosts, and causes chronic hepatitis, liver cirrhosis, and/or hepatocellular carcinoma in humans. During the infection the RNA genome of hepatitis C virus undergoes frequent missense mutations at one or two "hypervariable" regions within a presumptive envelope gene (Okamoto et al., 1992, Virology 190, 894-899; Ogata et al., 1991, Proc. Natl. Acad. Sci. USA 88, 3392-3396). In the present study, we analyzed three cases of hepatitis C virus infection, two in chimpanzees and one in humans, for the antigenicity of peptides predicted from the hypervariable region of viral RNA obtained during the follow-up. Our results showed a successive appearance of hepatitis C virus mutants with antigenically distinct amino acid sequence within the domain; and the amino acid replacement was associated with an alteration of predicted local secondary structure of the epitope region. Hence, the hypervariable domain of the hepatitis C virus envelope appeared to be structurally flexible and antigenically variable, providing the virus a way to escape from host immunity.

Amino Acid Sequence↗
PubMed1993

Determination of neuronal number and process surface area in organotypic cultures: a stereological approach.

Preparation of nervous tissue as an organotypic culture permits examination of nervous system development and interactions between neurons and with their environment. In order to evaluate the statistical significance of morphological changes, it is necessary to quantify tissue populations and parameters. Recent advances in stereology facilitate the gathering of morphometric data, while eliminating sources of error associated with traditional methods. Unfortunately, the new stereology has been perceived as complex and, therefore, has been slow to gain acceptance within neuroscience investigations in general and in vitro applications in particular. Here, we present a detailed application of the new, unbiased stereology to organotypic hippocampal cultures. These methods allow assessment of neuronal survival and morphological plasticity to culture conditions with increasing culture age. Neuronal number was assessed from point-sampled intercepts of cells sampled without bias by the selector procedure in vertical sections through hippocampal cultures. Surface area was estimated from profile intersects of neuronal processes with a cycloid array. The reference volume was determined by the Cavalieri method; this permitted expression of results as absolute values rather than as component densities. The importance of absolute values to valid interpretation of quantitative data is demonstrated by the results for neuronal number. The methods applied here provide a powerful approach to quantitation of organotypic cultures, and represent an important extension of qualitative studies of cultured nervous tissue.

Animals↗
PubMed1993

Bilateral accessory soleus: a report on four patients with partial fasciectomy.

Four young adults (average age 24 years) presented with complaints of posterior ankle pain after running. Bilateral accessory soleus muscles were diagnosed using magnetic resonance imaging or CT scan. Symptoms were present an average of 3 years before diagnosis. Two patients had previous surgery (ankle arthroscopy, tarsal tunnel release, and leg compartment release) before diagnosis and treatment. Obliteration of Kager's triangle (posterior ankle fat pad) was present on six out of eight lateral ankle radiographs. Posteromedial prominence was present on four out of eight ankles. Operative exploration confirmed the presence of five muscles and fasciectomy was performed. Follow-up (17 to 29 months) showed good relief of symptoms in all patients and return to long-distance running for three patients. Dissection of 47 preserved cadavers revealed three accessory soleus muscles in the 94 extremities (two muscles were bilateral in one cadaver).

Adolescent↗