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Biomedical subjects

A C Peterson

Publications and source records attributed to A C Peterson.

At least 19 recordsLinked to original sources
PubMed2004

Use of oral ketoconazole to prevent postoperative erections following penile surgery.

Analgesics and topical agents ineffectively inhibit painful erections after penile and urethral surgery. Oral ketoconazole reversibly inhibits testosterone production and has been used empirically at our institution to decrease postoperative erections. We performed a retrospective review of 38 patients who had undergone penile and urethral reconstructive surgery. In all, 31 patients received 400 mg of ketoconazole three times daily for 10-14 days postoperatively (the study group) and seven patients did not receive ketoconazole (the control group). The incidence of postoperative erections, pain, side effects, surgical outcomes and patient satisfaction in each group were compared. Of the control group, 71% reported erections in the immediate postoperative period, and all these patients reported the erections were painful. Only 23% of the patient taking ketoconazole reported postoperative erections, and only 16% reported the erections were painful. We conclude that ketoconazole effectively prevents painful postoperative erections with minimal side effects.

Administration, Oral↗
PubMed2001

Neurofilament cytoskeleton disruption does not modify accumulation of trophic factor mRNA.

Previously we described a transgenic mouse model in which neurofilaments are sequestered in neuronal cell bodies and withheld from the axonal compartment. This model and other transgenic models with disrupted neurofilaments are used widely to investigate the role of the neurofilament cytoskeleton in normal neurons and in inherited or acquired diseases. To interpret such studies, it is important to establish whether the maldistribution of neurofilaments has major secondary consequences on the cell biology of the affected neurons. Notably, multiple perturbations of the nervous system simultaneously affect both the neuronal cytoskeleton and neurotrophin expression. To determine whether the expression of neurotrophic factors or their receptors is perturbed by a primary disruption in neurofilaments, we compared the accumulated mRNA levels for ciliary neuroptrophic factor (CNTF), nerve growth factor, neurotrophin 3, and the alpha CNTF receptor in mature transgenic mice and their littermate controls. Consistently with the prolonged survival of neurons expressing atypical or abnormally distributed neurofilaments, no obvious changes were observed for any of the mRNA species examined.

Animals↗
PubMed2001

Widespread expression of netrin-1 by neurons and oligodendrocytes in the adult mammalian spinal cord.

Netrins are a family of secreted proteins that function as chemotropic axon guidance cues during neural development. Here we demonstrate that netrin-1 continues to be expressed in the adult rat spinal cord at a level similar to that in the embryonic CNS. In contrast, netrin-3, which is also expressed in the embryonic spinal cord, was not detected in the adult. In situ hybridization analysis demonstrated that cells in the white matter and the gray matter of the adult spinal cord express netrin-1. Colocalization studies using the neuronal marker NeuN revealed that netrin-1 is expressed by multiple classes of spinal interneurons and motoneurons. Markers identifying glial cell types indicated that netrin-1 is expressed by most, if not all, oligodendrocytes but not by astrocytes. During neural development, netrin-1 has been proposed to function as a diffusible long-range cue for growing axons. We show that in the adult spinal cord the majority of netrin-1 protein is not freely soluble but is associated with membranes or the extracellular matrix. Fractionation of adult spinal cord white matter demonstrated that netrin-1 was absent from fractions enriched for compact myelin but was enriched in fractions containing periaxonal myelin and axolemma, indicating that netrin-1 protein may be localized to the periaxonal space. These findings suggest that in addition to its role as a long-range guidance cue for developing axons, netrin may have a short-range function associated with the cell surface that contributes to the maintenance of appropriate neuronal and axon-oligodendroglial interactions in the mature nervous system.

Aging↗
PubMed2001

A unique role for Fyn in CNS myelination.

We analyzed the role of Fyn tyrosine kinase in CNS myelination by using fyn(-/-) null mutant mice, which express no Fyn protein. We found a severe myelin deficit in forebrain at all ages from 14 d to 1 year. The deficit was maximal at 1 month of age and was similar regardless of mouse strain background or whether it was determined by bulk isolation of myelin or by quantitation of myelin basic protein. To determine the cellular basis of the myelin deficit, we counted oligodendrocytes in tissue sections of mice expressing oligodendrocyte-targeted beta-galactosidase, and we used light and electron microscopy to examine the number and morphology of myelinated fibers and size of myelinated CNS structures. All of these parameters were reduced in fyn(-/-) mice. Unexpectedly, there were regional differences in the myelin deficit; in contrast to forebrain, fyn(-/-) cervical spinal cord exhibited no reduction in myelin content, number of oligodendrocytes, or number of myelinated fibers, nor was myelination delayed developmentally. We found that oligodendrocytes express Src, but there was no significant reduction of myelin content in null mutants lacking the Fyn-related kinases Src, Yes, or Lyn. Finally, we investigated the molecular features of Fyn that are required for myelination and found that a single amino acid substitution, which abolishes the tyrosine kinase activity of Fyn, resulted in a myelin deficit as great as that observed in the complete absence of Fyn protein. These results demonstrate that Fyn plays a unique role in myelination, one that requires its kinase activity.

Animals↗
PubMed2001

Plastibell template circumcision: a new technique.

A novel circumcision technique using the Plastibell as a template is described. This technique is fast and ensures excellent cosmesis compared with the standard sleeve circumcision. It is easy to perform and allows the urologist to achieve consistently excellent cosmetic results. We describe the technique in detail.

Circumcision, Male↗
PubMed2001

The prevalence of testicular microlithiasis in an asymptomatic population of men 18 to 35 years old.

PURPOSE: Testicular microlithiasis is an imaging entity of the testicle thought to be a marker of testicular cancer. To our knowledge the prevalence of testicular microlithiasis in an asymptomatic population at risk for testicular cancer is unknown. We report an ultrasound screening study done to establish the prevalence of testicular microlithiasis in an asymptomatic population. MATERIALS AND METHODS: Healthy men 18 to 35 years old from the annual Army Reserve Officer Training Corps training camp volunteered for study. A screening genitourinary history was obtained, and physical examination and screening scrotal ultrasound were performed. We defined testicular microlithiasis as more than 5 high intensity signals on ultrasound with each signal larger than 2 mm. We categorized testicular microlithiasis into microcalcifications that were scant-5 to 25 per side, moderate-greater than 25 per side but no areas of near confluence and too numerous to count. In all subjects with testicular microlithiasis tumor markers were also measured. RESULTS: Of 1,504 evaluated men with a mean age of 22.4 years, 84 (5.6%) had testicular microlithiasis, including 45 of 1,053 white (4%), 21 of 149 black (14.1%), 6 of 71 Hispanic (8.5%), 3 of 54 Asian or Pacific Island (5.6%) men and 9 of 174 (5.2%) who claimed no race affiliation. Tumor markers were normal in all subjects with testicular microlithiasis. CONCLUSIONS: Testicular microlithiasis occurs in more than 5% of healthy young men. In contrast, testicular cancer develops in 3/100,000 to 5/100,000 men or 1,000-fold less often. The relative prevalence of testicular microlithiasis with respect to testicular cancer, increased prevalence in minorities, bilateral distribution, and inverse geographic distribution of men with testicular microlithiasis and testicular cancer represent evidence against an association of the 2 conditions. This study indicates that testicular microlithiasis is a common finding in asymptomatic men that may not be related to testicular cancer.

Adolescent↗
PubMed2000

Model for focal demyelination of the spinal dorsal columns of transgenic MBP-LacZ mice by phototargeted ablation of oligodendrocytes.

Focal demyelination models provide powerful tools to study demyelination and remyelination in the central nervous system. In this report, we present a novel technique, which selectively targets oligodendrocytes within the spinal cord of transgenic mice to produce focal demyelination. Transgenic mice expressing the E. coli LacZ (beta-galactosidase) gene from the myelin basic protein promotor allowed for oligodendrocyte-specific cleavage of topically applied fluorescein-di-beta-galactopyranoside liberating photoactivatable fluorescein. Subsequent fluorescence illumination generated oxygen radicals that oxidized a second exogenous substrate, 3-amino-9-ethyl carbazole, to form a toxic precipitate within oligodendrocytes. Histochemical staining of the spinal cord dorsal columns 8 days following phototargeting revealed that the treated region no longer contained beta-galactosidase-positive cells. Focal demyelination of the dorsal columns was observed to a depth of 150 microm in transverse semithin plastic sections. Numerous bundles of naked axons interspersed with myelin, debris-laden macrophages, and reactive astrocytes were evident by electron microscopy. Remyelination of axons by both oligodendrocytes and invading Schwann cells was observed within the treated region 14 days after phototargeting. Newly generated oligodendrocytes were identified within the demyelinated region by their incorporation of bromodeoxyuridine. Thus, this novel focal demyelination protocol provides: (1) a method for selective targeted ablation of oligodendrocytes in vivo, (2) control over the extent of the demyelinated region, with (3) an environment that maintains its remyelination capacity. Phototargeted ablation of oligodendrocytes may therefore be a useful model for studying axon-glia interactions, axon regeneration within a demyelinated zone, and remyelination of axons.

Animals↗
PubMed1998

Pathogenesis of two axonopathies does not require axonal neurofilaments.

Neurofilaments are a major component of the axonal cytoskeleton and their abnormal accumulation is a prominent feature of the cytopathology encountered in several neurodegenerative diseases. Thus, an attractive and widely held model of pathogenesis involves the participation of disrupted neurofilaments as a common toxic intermediate. Here, in direct contrast to this hypothesis, we show that two neurodegenerative disease models in the mouse, dystonia musculorum (dt) and a superoxide dismutase 1 (SOD1)-mediated form of human motor neuron disease (amyotrophic lateral sclerosis, ALS), progress with little or no abatement on a transgenic background in which neurofilaments are withheld from the axonal compartment. By specifically excluding a necessary role for axonal neurofilaments, our observations redefine the components of the pathogenic pathway leading to axon disruption in these two degenerative diseases.

Actin Cytoskeleton↗
PubMed1998

Outcomes of varicocele ligation done for pain.

PURPOSE: Surgical ligation is an option in the management of patients with painful varicocele. Little objective data exist addressing the effectiveness of this treatment. We reviewed records from 58 patients who underwent varicocele ligation at our institution from January 1985 to May 1996 to establish success of surgical ligation of the painful varicocele. MATERIALS AND METHODS: ICD-9 billing codes were used to identify all patients who had undergone varicocele ligation for pain since 1985. We documented patient age, grade and location of varicocele, duration and quality of pain, response to conservative therapy and surgical approach to ligation. Telephone interviews and chart reviews were conducted to determine resolution of pain, complications of the procedure and if the patient would choose surgery again. RESULTS: We obtained followup on 35 of the 58 painful varicocele patients (60%). Average patient age was 25.7 years (range 15 to 65). The varicocele was on the left side in 30 men and bilateral in 5. Of the patients 31 described the pain as a dull throbbing ache, 2 as sharp and 2 as a pulling sensation. Initial conservative therapy failed in all 35 men. Varicocele was grade III in 18 cases, grade II in 16 and grade I in 1. The inguinal or subinguinal approach was used in 24 patients, high ligation in 10 and laparoscopic repair in 1. In 30 patients there was (86%) complete resolution of pain postoperatively and 1 had partial resolution. Only 4 patients (11%) had persistent or worse symptoms. CONCLUSIONS: This retrospective review supports the conclusion that varicocele ligation is an effective treatment for painful varicocele in properly selected patients.

Adolescent↗
PubMed1997

Increased severity of experimental autoimmune encephalomyelitis, chronic macrophage/microglial reactivity, and demyelination in transgenic mice producing tumor necrosis factor-alpha in the central nervous system.

Tumor necrosis factor-alpha (TNF-alpha) is an inflammatory cytokine implicated in a number of autoimmune diseases. Apoptotic cell death is induced by TNF-alpha in vitro, and has been suggested as one cause of autoimmune pathology, including autoimmune demyelinating diseases where oligodendrocytes are a target of immune attack. TNF-alpha also regulates macrophage activity which could contribute to autoimmune inflammation. We have expressed TNF-alpha at disease-equivalent levels in the central nervous system of transgenic mice, using a myelin basic protein (MBP) promoter. These mice were normal and showed no spontaneous pathology, but they developed experimental autoimmune encephalomyelitis (EAE) with greater severity than nontransgenic controls when immunized with MBP in adjuvant. Unlike nontransgenic controls, EAE then progressed to a nonabating demyelinating disease. Macrophage/microglial reactivity was evident in demyelinating lesions in spinal cord, but T cells were not detected during chronic disease. The participation of TNF-alpha in the demyelinating process is thus more probably due to the perpetuation of macrophage/microglial activation than to direct cytotoxicity of myelin or oligodendroglia.

Animals↗
PubMed1997

Factors contributing to recurrent carotid disease following carotid endarterectomy.

BACKGROUND: Retrospective analysis was performed to assess the effect of gender, age, hypertension, diabetes, and smoking upon residual disease, recurrent disease, and progression of disease following carotid endarterectomy (CE). The effect of patch versus primary closure was also studied. METHODS: Postoperative duplex studies were performed following 323 CEs at months 1, 6, 12, and 24. Residual disease was defined as luminal stenosis >59% at 1 month. Progression of disease was defined as stenosis at any month that was greater than stenosis at month 1. Recurrent disease was nonresidual stenosis >79%. RESULTS: Correlation was found between age at operation <65 years and cigarette smoking; both also correlated with progression of disease on serial studies, as well as recurrent stenosis <79%. Primary closure of the arteriotomy correlated with residual disease. CONCLUSION: Primary closure of the arteriotomy following CE increases the likelihood of residual disease. Smokers and those aged <65 years are predisposed to progression of postoperative disease, and to development of recurrent stenosis.

Age Factors↗
PubMed1997

Tissue-specific selection for different mtDNA genotypes in heteroplasmic mice.

Mammalian mitochondrial DNA (mtDNA) is a highly polymorphic, high-copy-number genome that is maternally inherited. New mutations in mtDNA segregate rapidly in the female germline due to a genetic bottleneck in early oogenesis and as a result most individuals are homoplasmic for a single species of mtDNA. Sequence variants thus accumulate along maternal lineages without genetic recombination. Most of the extant variation in mtDNA in mammalian populations has been assumed to be neutral with respect to selection; however, comparisons of the ratio of replacement to silent nucleotide substitutions between species suggest that the evolution of mammalian mtDNA is not strictly neutral. To test directly whether polymorphic mtDNAs behave as neutral variants, we examined the segregation of two different mtDNA genotypes in the tissues of heteroplasmic mice. We find evidence for random genetic drift in some tissues, but in others strong, tissue-specific and age-related, directional selection for different mtDNA genotypes in the same animal. These surprising data suggest that the coding sequence of mtDNA may represent a compromise between the competing demands of different tissues and point to the existence of unknown, tissue-specific nuclear genes important in the interaction between the nuclear and mitochondrial genomes.

Age Factors↗
PubMed1996

Multipotent CNS stem cells are present in the adult mammalian spinal cord and ventricular neuroaxis.

Neural stem cells in the lateral ventricles of the adult mouse CNS participate in repopulation of forebrain structures in vivo and are amenable to in vitro expansion by epidermal growth factor (EGF). There have been no reports of stem cells in more caudal brain regions or in the spinal cord of adult mammals. In this study we found that although ineffective alone, EGF and basic fibroblast growth factor (bFGF) cooperated to induce the proliferation, self-renewal, and expansion of neural stem cells isolated from the adult mouse thoracic spinal cord. The proliferating stem cells, in both primary culture and secondary expanded clones, formed spheres of undifferentiated cells that were induced to differentiate into neurons, astrocytes, and oligodendrocytes. Neural stem cells, whose proliferation was dependent on EGF+bFGF, were also isolated from the lumbar/sacral segment of the spinal cord as well as the third and fourth ventricles (but not adjacent brain parenchyma). Although all of the stem cells examined were similarly multipotent and expandable, quantitative analyses demonstrated that the lateral ventricles (EGF-dependent) and lumbar/sacral spinal cord (EGF+bFGF-dependent) yielded the greatest number of these cells. Thus, the spinal cord and the entire ventricular neuroaxis of the adult mammalian CNS contain multipotent stem cells, present at variable frequency and with unique in vitro activation requirements.

Animals↗
PubMed1996

Visualization of slow axonal transport in vivo.

In axons, cytoskeletal constituents move by slow transport. However, it remains controversial whether axonal neurofilaments are dynamic structures in which only subunits are transported or whether filaments assemble in the proximal axon and are transported intact as polymers to the axon terminus. To investigate the form neurofilament proteins take during transport, neurons of transgenic mice lacking axonal neurofilaments were infected with a recombinant adenoviral vector encoding epitope-tagged neurofilament M. Confocal and electron microscopy revealed that the virally encoded neurofilament M was transported in unpolymerized form along axonal microtubules. Thus, neurofilament proteins are probably transported as subunits or small oligomers along microtubules, which are major routes for slow axonal transport.

Adenoviridae↗
PubMed1996

Determination of neuroepithelial cell fate: induction of the oligodendrocyte lineage by ventral midline cells and sonic hedgehog.

Near the floor plate of the embryonic neural tube there is a group of neuroepithelial precursor cells that are specialized for production of the oligodendrocyte lineage. We performed experiments to test whether specification of these neuroepithelial oligodendrocyte precursors, like other ventral neural cell types, depends on signals from the notochord and/or floor plate. We analyzed heterozygous Danforth's short tail (Sd/+) mutant mice, which lack a notochord and floor plate in caudal regions of the neural tube, and found that oligodendrocyte precursors did not appear at the ventricular surface where there was no floor plate. Moreover, oligodendrocytes did not develop in explant cultures of Sd/+ spinal cord in the absence of a floor plate. When a second notochord was grafted into an ectopic position dorsolateral to the endogenous notochord of a chicken embryo, an additional floor plate was induced along with an ectopic focus of oligodendrocyte precursors at the ventricular surface. Oligodendrocytes developed in explants of intermediate neural tube only when they were cocultured with fragments of notochord or in the presence of purified Sonic hedgehog (Shh) protein. Thus, signals from the notochord/floor plate, possibly involving Shh, are necessary and sufficient to induce the development of ventrally derived oligodendroglia. These signals appear to act by specifying the future fate(s) of neuroepithelial cells at the ventricular surface rather than by influencing the proliferation or differentiation of prespecified progenitor cells in the parenchyma of the cord.

Animals↗