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Biomedical subjects

A Freese

Publications and source records attributed to A Freese.

At least 19 recordsLinked to original sources
PubMed1998

In vivo expression of therapeutic human genes for dopamine production in the caudates of MPTP-treated monkeys using an AAV vector.

An adeno-associated virus (AAV) vector, expressing genes for human tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC), demonstrated significantly increased production of dopamine in 293 (human embryonic kidney) cells. This bicistronic vector was used to transduce striatal cells of six asymptomatic but dopamine-depleted monkeys which had been treated with the neurotoxin MPTP. Striatal cells were immunoreactive for the vector-encoded TH after stereotactic injection for periods up to 134 days, with biochemical effects consistent with dopamine biosynthetic enzyme expression. A subsequent experiment was carried out in six more severely depleted and parkinsonian monkeys. Several TH/aadc-treated monkeys showed elevated levels of dopamine near injection tracts after 2.5 months. Two monkeys that received a beta-galactosidase expressing vector showed no change in striatal dopamine. Behavioral changes could not be statistically related to the vector treatment groups. Toxicity was limited to transient fever in several animals and severe hyperactivity in one animal in the first days after injection with no associated histological evidence of inflammation. This study shows the successful transfection of primate neurons over a period up to 2.5 months with suggestive evidence of biochemical phenotypic effects and without significant toxicity. While supporting the idea of an in vivo gene therapy for Parkinson's disease, more consistent and longer lasting biochemical and behavioral effects will be necessary to establish the feasibility of this appraoch in a primate model of parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

Analysis of harvest morbidity and radiographic outcome using autograft for anterior cervical fusion.

STUDY DESIGN: Retrospective study of 184 autologous iliac crest bone grafts used for anterior cervical fusion in 144 procedures. OBJECTIVES: To evaluate the effect of autologous iliac crest bone graft harvest site on operation and recovery and to identify patients at risk for harvest morbidity. SUMMARY OF BACKGROUND DATA: Although autologous iliac crest bone graft is considered the most successful grafting material, concerns about harvest morbidity provide a rationale for considering allograft. Data about the use of autograft therefore would assist spinal surgeons in selecting the appropriate substrates for fusion after anterior cervical decompression. METHODS: Statistical analysis based on patient gender, smoking history, obesity, and medical or pharmacologic risk factors for wound healing was used to evaluate morbidity after patient interviews and examinations. Limited assessment of radiographic outcome also was performed. RESULTS: A second operation because of donor site morbidity was performed in four patients (2.8%), but only one (0.7%) with meralgia paresthetica had permanent sequelae. Superficial wound infection or dehiscence occurred in 5.6% of patients, with a disproportionate number of women, obese patients, and those with medical risk represented. Protracted wound symptoms of pain and poor cosmesis were reported in 2.8% and 3.5% of patients, respectively, and also were found in a significant number of female and obese patients. Evidence of fusion was present in 97% of cases. CONCLUSION: Autologous iliac crest bone graft harvest results in minimal major morbidity when regional anatomy is respected and careful technique is observed. The identification of patients at risk for minor complications suggests that allograft may be appropriate in these patients; however, prospective comparison is required to identify whether graft material or technical factors determine fusion success and relative benefit.

Adult↗
PubMed1997

Parkinson's disease: the case for novel treatment strategies.

Over the past 30 years, significant strides have been made toward improving symptomatic therapy of patients with Parkinson's disease. However, limitations persist, and the incremental improvement each new drug offers a patient yields only a minimal advantage therapeutically. Therefore, to alter meaningfully the natural course of this debilitating disorder, which becomes more prevalent each year in our society, significant novel therapeutic approaches must be tested. Genetic intervention in Parkinson's disease may offer an entirely different method for treating this disease in the future, based not only on symptomatic therapy, but also on neuroprotective and/or neuroregenerative therapy which would alter the natural history of relentless progression.

Antiparkinson Agents↗
PubMed1997

Adenovirus vector-mediated gene transfer into human epileptogenic brain slices: prospects for gene therapy in epilepsy.

As a first step in the development of a gene therapy approach to epilepsy, we evaluated the ability of adenovirus vectors to direct the transfer into and expression of a marker gene in human brain slices obtained from patients undergoing surgery for medically intractable epilepsy. Following injection of adenovirus vectors containing the Escherichia coli lacZ gene into hippocampal and cortical brain slices, lacZ mRNA, beta-galactosidase protein, and enzymatic activity were detected, confirming successful gene transfer, transcription, and translation into a functional protein. Transfected cells were predominantly glial, with some neurons expressing beta-galactosidase as well. These results support the potential of adenovirus vectors to transfer genetic information into human epileptogenic brain, resulting in expression of the gene into a functional protein. These findings also have implications for the development of gene therapy approaches to certain seizure disorders. A number of potential therapeutic approaches are discussed, including the elevation of inhibitory neurotransmitter or neuropeptide levels, expression or modulation of postsynaptic receptors, and manipulation of signal transduction systems.

Adenoviruses, Human↗
PubMed1997

Direct gene transfer into human epileptogenic hippocampal tissue with an adeno-associated virus vector: implications for a gene therapy approach to epilepsy.

PURPOSE: Virus vectors capable of transferring genetic information into human cells provide hope for improved therapy in several neurological diseases, including epilepsy. We evaluated the ability of an adeno-associated virus (AAV) vector to transfer and cause expression of a lacZ marker gene in brain slices obtained from patients undergoing temporal lobectomy for control of medically intractable seizures. METHODS: Human brain slices were injected with an AAV vector (AAVlacZ) encoding Escherichia coli beta-galactosidase and incubated for as long as 24 h. The presence of lacZ mRNA. beta-galactosidase protein and enzymatic activity were assayed by reverse transcriptase polymerase chain reaction (rtPCR), immunocytochemistry, and the X-Gal technique, respectively. RESULTS: AAVlacZ directed the expression in human epileptogenic brain of E. coli beta-galactosidase that had functional activity. Expression was observed in < or =5 h and was sustained for as long as the slices were viable. Morphological analysis indicated that neurons were preferentially transfected, and there was no evidence of cytotoxicity. CONCLUSIONS: Our results confirm the feasibility of using AAV vectors to transfer genes into the human CNS and in particular, into neurons. Replacement of the lacZ gene with a functional gene modulating hippocampal neuronal physiology, might allow a localized genetic intervention for focal seizures based on the stereotaxic or endovascular delivery of such a vector system into the appropriate brain region.

Dependovirus↗
PubMed1997

Further characterization and in situ localization of chain-like aggregates of the gliding bacteria Myxococcus fulvus and Myxococcus xanthus.

For the first time, chain-like aggregates, called "strands," have been enriched from crude cell wall preparations of liquid-grown vegetative cells of two strains of Myxococcus xanthus. These strands are highly isomorphic to macromolecular structures, previously described for Myxococcus fulvus (Lünsdorf and Reichenbach, J. Gen. Microbiol. 135:1633-1641, 1989). The strands are morphologically composed of ring elements, consisting of six or more peripheral protein masses and possibly three small central masses. The ring elements are linked by two parallel strings of filamentous proteins, called elongated elements, which keep the ring elements at a constant distance. The overall dimensions of the ring elements are 16.6 +/- 1.0 nm (n = 55) for M. xanthus Mx x48 and 16.4 +/- 1.5 nm (n = 37) for M. xanthus DK 1622. The distance between the ring elements, as a measure of the length of the elongated elements, is 16.6 +/- 1.1 nm (n = 59) for strain Mx x48 and 15.5 +/- 0.6 nm (n = 41) for strain DK 1622. Characteristically, the strands and oligomeric forms thereof show a strict association with the outer membrane. In situ studies of freeze-fractured cells of M. fulvus showed ring elements, isomorphic to those described for M. xanthus, within the periplasm; they appeared in parallel rows just below the outer membrane but not in direct contact with the cytoplasmic membrane. A three-dimensional model summarizes the morphological data. It is hypothesized that the chain-like strands, as building blocks of a more complex belt-like continuum, represent the peripheral part of the gliding machinery, which transforms membrane potential energy into mechanical work.

Bacterial Proteins↗
PubMed1997

Outcome analysis for adults with spondylolisthesis treated with posterolateral fusion and transpedicular screw fixation.

The outcomes of 52 adult patients with symptomatic low-grade spondylolisthesis treated with autologous posterolateral arthrodesis and pedicle screw fixation were retrospectively reviewed. Although a 90% rate of successful fusion was obtained using this technique, only 60% of patients were considered to have good outcomes. Treatment failures consisted mostly of back pain and were not predicted by preoperative symptoms. Compensation claims and smoking had very significant adverse impacts on both employment and pain results despite high fusion rates, particularly in patients under the age of 55 years. Overall, patients who required more than one operation demonstrated poor outcomes compared to those who only needed one. However, patients with at least two prior operations or preoperative pseudoarthrosis fared particularly poorly, whereas those who had undergone only one prior surgery and had no attendant compensation issue reported good results. A trend toward poor outcome was observed in patients with postlaminectomy spondylolisthesis, versus those with isthmic or degenerative etiologies. Gender did not exert an impact on outcome. The authors conclude that autologous posterolateral arthrodesis combined with pedicle screw fixation resulted in a high fusion rate, and contributed to successful outcomes in the treatment of certain subgroups of adults with spondylolisthesis. In the absence of other risk factors, patients may obtain significant benefit from surgery despite older age and a single failed operation. Careful patient selection appears critical in predicting the maximum benefit from this technique.

Adult↗
PubMed1997

MR of thoracic cord compression caused by epidural extramedullary hematopoiesis in myelodysplastic syndrome.

Spinal cord compression caused by extramedullary hematopoiesis is a rare complication of chronic anemic states, most frequently occurring in patients with beta-thalassemia. We report the MR appearance of extramedullary hematopoiesis resulting in cord compression in a patient with a myelodysplastic syndrome, which was isointense with the spinal cord on T1-weighted images and markedly hypointense on fast spin-echo T2-weighted images, and that demonstrated enhancement.

Aged↗
PubMed1996

Prospects for gene therapy in Parkinson's disease.

Numerous advances in in vivo and ex vivo gene-therapy approaches to Parkinson's disease offer promise for direct clinical trials in patients in the next several years. These systems are predicated on introducing gene that encode enzymes responsible for dopamine biosynthesis or neurotrophic factors that may delay nigrostriatal degeneration or facilitate regeneration. We review the current status of experimental approaches to gene therapy for Parkinson's disease. Comparative advantages and disadvantages of each system are enumerated, and preclinical trials of some of the systems are evaluated. Although the specific in vivo or ex vivo methods used for gene transfer into the brain are likely to be supplanted by newer technology over the next decade, the principles and approaches developed in current studies likely will remain the same.

Adenoviridae↗
PubMed1996

Rat MHC class I peptides are immunogenic.

We postulated that indirect recognition of MHC-derived peptides might modulate the alloresponse to donor antigen. In this study, we looked at the potential of two class I peptides derived from the alpha 1 and alpha 2 regions of the DA RT1Aa molecule. Lew responder rats were immunized by varying concentrations of two 25mer peptides covering residues 56-81 and 96-120. The injections were under the footpad and were repeated on day 14. The thickness of the footpads was measured to control delayed-type hypersensitivity (DTH). The animals were sacrificed on day 16 and the splenocytes were tested in mixed lymphocyte culture as responders against DA stimulator cells and CAP third-party splenocytes. In addition, the phenotype of the cells was measured using flow cytometry with antibodies against CD4, CD8, CD5, MHC class II, CD25, CD14 and CD19. Peptide 96-120 induced strong sensitization of the Lew recipient animals at concentrations of 200-500 micrograms (n = 4). The stimulation index was 2-3 times higher than that of untreated animals. Peptide 56-81 failed to induce sensitization at the concentrations used, but surprisingly induced a concentration-dependent immunosuppression that was highest at 400 micrograms (n = 4). In proliferation experiments responder Lew rats proliferated only to peptide 56-81 in vitro.

Amino Acid Sequence↗
PubMed1996

Determination of HLA-B7 T-cell epitopes.

A series of peptides derived from the alpha 1 and alpha 2 regions of the HLA-B7 and HLA-A2 molecules was synthesized with an automatic peptide synthesizer using the FMOC (9-fluorenylmethoxycarbonyl) technique. Peptides were analyzed and purified by reversed-phase high pressure liquid chromatography (HPLC). Peptide purity was > 96%. The effect of B7 peptides on mixed lymphocyte cultures was tested in vivo. The alloresponse in the cultures with B7 peptides was strongly enhanced. The peptides that were most effective inhibited cytotoxic T-lymphocyte (CTL) cytolysis. The data show that the peptides are immunogenic and that they are recognised by both the direct and indirect pathways. Further, the mechanism of peptide recognition was studied. We coupled peptide B7 (residues 62-70 in HLA-B7) and peptide A2 (residues 62-70 in HLA-B2) covalently to fluorescein isothiocyanate (FITC). B7-specific CTLs were incubated with these peptides at 37 degrees C for 90 min and cell fluorescence measured by flow cytometry. The B7 peptide was bound by 60% of the CTLs whereas the A2 peptide, as a negative control, bound only 10%. The molecular size of the ligands to which the peptides bind are being characterized by immunoprecipitation.

Amino Acid Sequence↗
PubMed1996

Hippocampal cell distributions in temporal lobe epilepsy: a comparison between patients with and without an early risk factor.

Neuronal cell distributions were measured for anterior and posterior locations in the hippocampi of epilepsy patients who were seizure-free after temporal lobectomy. Patients were divided into two groups, those with an early risk factor, defined as a neurologic insult occurring in the first 4 years of life, and those with no early risk factor. Early-risk patients had lower hilar cell densities, lower granule cell densities, and fewer granule cells per millimeter, a measured related to total granule cell number, than to early risk patients. Moreover, each risk group had different anteroposterior density gradients for granule cells and hilar cells. These differences in cell distribution may arise from different patterns of cell loss of cell migration in the dentate gyrus during development. In the early-risk group, there was also a distinction between patients with a history of febrile convulsions without CNS infection and patients with a history of meningitis or encephalitis. These two subgroups had similar numbers of granule cells, However, the meningitis/encephalitis subgroup exhibited a wider granule cell layer, suggesting that the granule cell layer was more dispersed. Our results support the hypothesis of a predominantly anterior hippocampal insult in temporal lobe epilepsy (TLE). In nonepileptic hippocampus, the ratio of putatively excitatory granule neurons to putatively inhibitory hilar neurons is highest in the anterior hippocampus. This ratio may explain in part why the anterior hippocampus is more prone to cell loss and seizures.

Adult↗
PubMed1996

Transfection of human lactotroph adenoma cells with an adenovirus vector expressing tyrosine hydroxylase decreases prolactin release.

Pituitary adenomas are common intracranial neoplasms, for which surgery and radiation are usually not curative. In attempting to develop gene therapy as a better approach to treating pituitary adenomas, we chose lactotroph adenomas as a model. The rationale for the use of this model is based on the observation that dopamine agonists decrease prolactin secretion by lactotroph adenomas, and also decrease their size. We transfected primary cultures of human lactotroph adenoma cells with an adenovirus vector containing a cDNA which encodes a human tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine. Transfection induced expression of tyrosine hydroxylase and increased production of dopamine, resulting in the predicted biologic effect of decreased prolactin secretion. These results demonstrate the potential for gene therapy of lactotroph adenomas and perhaps other pituitary adenomas, which are less amenable to pharmacologic treatment than lactotroph adenomas.

Adenoma↗
PubMed1995

An HSV-1 vector expressing tyrosine hydroxylase causes production and release of L-dopa from cultured rat striatal cells.

In this report we demonstrate that a defective herpes simplex virus type one (HSV-1) vector can express enzymatically active tyrosine hydroxylase in cultured striatal cells that are thereby converted into L-DOPA-producing cells. A human tyrosine hydroxylase cDNA (form II) was inserted into an HSV-1 vector (pHSVth) and packaged into virus particles using an HSV-1 strain 17 mutant in the immediate early 3 gene (either ts K or D30EBA) as helper virus. Cultured fibroblasts were infected with pHSVth and 1 day later tyrosine hydroxylase immunoreactivity and tyrosine hydroxylase enzyme activity were observed. The tyrosine hydroxylase enzyme activity directed the production of L-DOPA. pHSVth infection of striatal cells in dissociated cell culture resulted in expression of tyrosine hydroxylase RNA and tyrosine hydroxylase immunoreactivity. Release of L-DOPA and low levels of dopamine were observed from cells in pHSVth-infected striatal cultures. Expression of tyrosine hydroxylase and release of catecholamines were maintained for at least 1 week after infection.

Animals↗
PubMed1994

The application of 5-bromodeoxyuridine in the management of CNS tumors.

A variety of clinical reports have described the application of the bromodeoxyuridine labeling index as an adjunct to conventional pathological examination of CNS tumors. This index has proven useful in predicting the clinical outcome associated with many such tumors. Furthermore, because of its efficacy as a radiosensitizing agent, bromodeoxyuridine (and the closely related iododeoxyuridine) has been used in combination with radiation therapy for malignant glial neoplasms, with some encouraging results. Although most studies suggest that bromodeoxyuridine is safe, there is evidence that this compound does have potential side-effects, including the observation that it is a mutagen and carcinogen in some experimental systems. A number of new alternative approaches for predicting the clinical outcome of CNS tumors has been developed based on an increased understanding of their molecular biology. However, until such approaches are better characterized, the clinical application of bromodeoxyuridine will continue to play an important role in predicting the clinical behavior of many CNS tumors.

Brain Neoplasms↗
PubMed1993

Long-term increases in neurotransmitter release from neuronal cells expressing a constitutively active adenylate cyclase from a herpes simplex virus type 1 vector.

Signal-transduction pathways mediate a wide range of short-term changes in the physiology of neuronal systems from invertebrates to mammals. However, examples of long-term changes in neuronal physiology mediated by these pathways have been limited to invertebrate systems. In this report, long-term changes in the physiology of mammalian neurons were studied by using genetic intervention to cause a long-lasting activation of the cAMP pathway. The catalytic domain of yeast adenylate cyclase (cyr), encoding a constitutive enzyme activity, was expressed in neuronal cells infected with a defective herpes simplex virus vector (pHSVcyr). In PC-12 cells infected with pHSVcyr, increases were seen in cAMP levels, protein kinase A activity, protein phosphorylation, phosphorylation of the tyrosine hydroxylase protein kinase A site (Ser40), and catecholamine release. Infection of sympathetic neurons with pHSVcyr increased cAMP levels, protein phosphorylation, and catecholamine release. Yeast adenylate cyclase immunoreactivity and elevated cAMP levels were localized to the cell bodies of sympathetic neurons. The increase in neurotransmitter release was both Ca(2+)- and activity-dependent and persisted for at least 1 week after infection of the sympathetic neurons, suggesting that sustained physiological activation of the cAMP pathway may mediate long-term changes in the neuronal physiology of mammalian systems.

Adenylyl Cyclases↗
PubMed1993

Superficial siderosis of the central nervous system: magnetic resonance imaging and pathological correlation. Case report.

The authors report a 32-year-old woman who had undergone repair of an occipital encephalocele in infancy and who experienced a 20-year history of progressive hearing loss and intermittent vertigo. After parturition, she developed a rapidly progressive quadriparesis and brain-stem dysfunction associated with persistent intraventricular and subarachnoid hemorrhage. Serial magnetic resonance (MR) images showed progressive deposition of hemosiderin along the surface of the brain, brain stem, and spinal cord, and enhanced thickened membranes at the site of the original encephalocele repair. Posterior fossa exploration disclosed hemorrhagic membranes, which were resected; despite removal of this tissue, the patient deteriorated and died. Postmortem examination confirmed iron-containing pigment along the meninges, cerebral hemispheres, brain stem, spinal cord, and cranial nerves accompanied by atrophy of the superficial cerebellar cortex. It is concluded that superficial siderosis may accompany encephalocele repair. This is believed to be the first report in the literature of superficial siderosis of the central nervous system to correlate in vivo MR images with autopsy results.

Adult↗