PubMed Health⌕ Search

Biomedical subjects

L A Hansen

Publications and source records attributed to L A Hansen.

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

A transgenic mouse model (TG.AC) for skin carcinogenesis: inducible transgene expression as a second critical event.

The v-Ha-ras transgenic TG.AC mouse line behaves as a genetically initiated model for mouse skin tumorigenesis with enhanced susceptibility to skin carcinogens. TG.AC mice develop epidermal papillomas in fewer than 20 weeks in response to the topical application of a variety of chemicals such as complete carcinogens, phorbol ester-type tumor promoters, and nonphorbol ester-type tumor promoters as well as to full-thickness skin wounds or plucking of the dorsal hair. We have found that the pedunculated epidermal papillomas can arise as focal hyperplasias from the permanent portion of the follicular epithelium. Expression of the v-Ha-ras transgene serves as a marker for tumor development since it is expressed at significant levels in the papilloma precursors, focal follicular hyperplasias, and the papillomas but not in the surrounding skin. Transgene expression colocalizes with increased cell proliferation in the papillomas as compared to non-tumor bearing surrounding skin. Malignant skin tumors, primarily squamous cell carcinomas and sarcomas, develop from sites of papilloma development in approximately 40% of papilloma bearing mice. As well as significant levels of transgenic v-Ha-ras expression, some of the malignancies also exhibit karyotypic changes which include trisomy of chromosome six or fifteen, but not chromosome seven. We believe that the TG.AC mouse line serves not only as a model for studying the mechanisms of skin tumorigenesis, but will also be a useful adjunct to the two year NTP toxicity/carcinogenicity studies by identifying carcinogens in fewer than 20 weeks.

Animals↗
PubMed1994

Apolipoprotein-E epsilon-4 is associated with increased neurofibrillary pathology in the Lewy body variant of Alzheimer's disease.

Brains from demented patients with both Alzheimer's disease (AD) pathology and brainstem and neocortical Lewy bodies have fewer neurofibrillary tangles than pure AD, but share with AD an increased apolipoprotein-E epsilon-4 (APOE4) allelic frequency. We applied the Braak and Braak AD neuropathology staging protocol, based on entorhinal and neocortical neurofibrillary pathology, to 40 such Lewy body variants of AD (LBV) and 97 cases of pure AD and compared the results in APOE4 positive and APOE4 negative subgroups. APOE4 was associated with more severe neurofibrillary pathology in LBV but not in pure AD, where a ceiling effect appears to be operative.

Aged↗
PubMed1994

Follicular origin of epidermal papillomas in v-Ha-ras transgenic TG.AC mouse skin.

A follicular origin for some skin tumors has been hypothesized in both humans and animal models. Because of its rapid and sensitive response to tumor promoter treatment, a v-Ha-ras transgenic (TG.AC) mouse line was used to determine the origins of epidermal papillomas. Using histological studies and transgene expression as a marker for papilloma development, we determined that pedunculated papillomas arose from focal hyperplasias of the permanent portion of the follicular epithelium in phorbol 12-myristate 13-acetate-treated TG.AC mouse skin. Damage to the hair follicle by depilation was also sufficient to induce papillomas that were histologically indistinguishable from those produced by chemical exposure. Identification of the cellular origins of papillomas in this transgenic mouse model will allow for an analysis of the role of the hair follicle and hair cycle-associated signaling in tumor development.

Animals↗
PubMed1994

Clinical-neuropathological correlations in Alzheimer's disease and related dementias.

OBJECTIVE: To compare neurologists' initial clinical diagnoses made according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) and Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition guidelines with neuropathological diagnoses of Alzheimer's disease (AD) and related dementias. DESIGN: Consecutive autopsies in a prospective cohort study. SETTING: Community-dwelling patients with dementia referred to neurologists at an Alzheimer's Disease Research Center and satellite clinics (n = 151) and patients initially evaluated when institutionalized (n = 19). PATIENTS: Of 204 elderly patients who had an autopsy performed, 170 had received a complete dementia evaluation according to NINCDS-ADRDA guidelines. MAIN OUTCOME MEASURES: Percentage agreement between neurologists' initial clinical diagnoses and pathological findings. RESULTS: Of 137 patients clinically diagnosed as having probable or possible AD, 123 (90%) had AD neuropathological findings; this included 29 with AD accompanied by Lewy bodies, and 14 with AD and one or more infarcts. Cases of vascular and mixed dementia (AD and infarct[s]) had lower rates of agreement with pathological findings. Possible AD cases were more likely than probable AD cases to show pathological features other than AD. Clinicians predicted the presence or absence of AD pathological findings significantly better than chance. In patients with AD pathological lesions, older age of onset and male gender were significantly associated with shorter duration from disease onset to death. CONCLUSIONS: Clinicians accurately predicted AD pathological findings or their absence in most cases. Attributing other degenerative dementias to AD, misdiagnosing patients with combined AD and Lewy bodies and misjudging the vascular contribution to dementia were the major areas of inaccuracy. Formal criteria for dementia associated with non-AD lesions, Lewy bodies, and infarcts need to be developed and tested.

Aged↗
PubMed1994

Oral ondansetron pharmacokinetics: the effect of chemotherapy.

The effect of a typical 5-day chemotherapy treatment with cisplatin (20-40 mg/m2 per day) and 5-fluorouracil (5-FU, 1 gm/m2 per day) on the pharmacokinetics of ondansetron was investigated. Twenty cancer patients received 8 mg of ondansetron in three periods, including an oral tablet on day 1, an intravenous infusion on day 4, and an oral tablet on day 5. Absolute bioavailability after the oral dosing on day 1 was 87.5 +/- 31.3%, and on day 5 was 85.2 +/- 22.1% (P > .05). Mean values of AUC, Cmax, Tmax, and half life on days 1 and 5 were 399 +/- 275 and 381 +/- 222 ng.hour/mL, 53.3 +/- 26.8 and 43.6 +/- 21.7 ng/mL, 1.9 +/- 1.4 and 2 +/- 1.4 hours, and 5.21 +/- 1.78 and 6.19 +/- 1.99 hours, respectively. These values were not significantly different (P > .05). In summary, this study showed that cisplatin and 5-FU did not significantly alter the pharmacokinetics of oral ondansetron in cancer patients during the 5 days of chemotherapy. Oral bioavailability of ondansetron appeared to be greater in cancer patients than in healthy subjects.

Administration, Oral↗
PubMed1994

Focal transgene expression associated with papilloma development in v-Ha-ras-transgenic TG.AC mice.

The homozygous transgenic mouse line TG.AC contains a v-Ha-ras transgene and rapidly develops epidermal papillomas in response to either wounding or treatment with tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA). The transgenic v-Ha-ras protein product was detected in all papillomas removed from TPA-treated TG.AC mice but not in vehicle- or TPA-treated TG.AC skin without tumors. In situ hybridization demonstrated that focal expression of the transgene was limited to regions of papilloma development and further localized the expression of the transgene message to the epidermal component of the papillomas, with the strongest signal in the basal epidermoid cells. Cellular proliferation, as indicated by immunohistochemical staining for proliferating-cell nuclear antigen (PCNA), was similarly localized primarily to basal epidermoid cells and, to a lesser extent, stratum spinosum cells in all papillomas analyzed. Cells that stained positively for PCNA were much more common in the papillomas than in the surrounding, normal-appearing skin. The focal nature of papilloma development was also evidenced by protein kinase C activity and hyperplasia after TPA treatment. As early as 18 d after the start of TPA treatment, focal hyperplasias associated with the follicular epidermis were observed in TG.AC but not nontransgenic FVB/N skin; these hyperplasias were assumed to be the precursors of the epidermal papillomas. To explain the development of transgene-expressing tumors from apparently transgene-negative, normal-appearing skin, we hypothesize that the papillomas arise from the clonal expansion of focal areas of epidermal cells that overexpress the transgene. We also propose that the TG.AC line is an excellent model for studying very early events in papillomagenesis.

Animals↗
PubMed1994

Micropuncture and cannulation studies of fluid composition and transport in the ductuli efferentes testis of the rat: comparisons with the homologous metanephric proximal tubule.

Luminal fluids were collected in vivo by micropuncture and cannulation from the rete testis, efferent ducts and ductus epididymidis of the rat to determine the composition of efferent duct fluids and the rates of reabsorption of water and solutes by the efferent ducts. The concentration of spermatozoa increased by a factor of about 25 from 2.42 x 10(4) microliters-1 in the fluid from the rete testis to 6.00 x 10(5) microliters-1 in fluid at the end of the efferent ducts, indicating that 96.2% of the fluid leaving the testis is reabsorbed from the lumen of the efferent ducts. Most of this reabsorption (70.9% or 33.4 microliters h-1) occurs in the region between the rete testis and the middle of the coni vasculosi, with only 25.1% (11.8 microliters h-1) occurring between the coni and the beginning of the ductus epididymidis. However, reabsorption across the epithelium occurs at about the same rate in both regions, with the proximal region reabsorbing 17.2 microliters cm-2 h-1 (70.9% of fluid entering the region) and the distal region reabsorbing 12.2 microliters cm-2 h-1 (86.1% of fluid entering the region). Consequently, the fluid reabsorption rate for the whole efferent duct system (15.6 microliters cm-2 h-1) is similar to the values for individual regions. The principal solutes in luminal fluids from the efferent ducts are Na+ (137-144 mM) and Cl- (113-130 mM). The estimated sum contribution of Na+, Cl- and K+ to the osmotic pressure of luminal fluids was approximately 80% at each site sampled in the efferent ducts. The osmotic pressure of luminal fluid samples (301-307 mosmol kg-1) did not vary significantly along the ducts or differ significantly from that of blood plasma. The results demonstrate that there is a net reabsorption in the efferent ducts of nearly all the testicular output of water and inorganic electrolytes, and most of the protein, and that, in comparison, the ductus epididymidis is a negligible site of net fluid reabsorption. The results indicate that the ductus epididymidis, rather than the efferent ducts, is the site of accumulation of high concentrations of specific organic compounds like inositol. The efferent ducts are similar to the homologous proximal tubules of the metanephric kidney in that the luminal electrolyte composition (principal solutes Na+ and Cl-) and osmotic pressure remain relatively stable and that fluid reabsorption is close to isotonic and occurs at the same rate as the reabsorption of Na+.

Absorption↗
PubMed1994

Delayed neutropenia with ticlopidine.

OBJECTIVE: To report a case of ticlopidine-induced neutropenia occurring 18 days after discontinuation of the drug. CASE SUMMARY: A 68-year-old woman was placed on ticlopidine after a transient ischemic attack. Ten days later the drug was discontinued because the patient developed a rash. Eighteen days later she developed pneumonia and neutropenia, which were believed to be induced by ticlopidine. DISCUSSION: Drug-induced neutropenia is serious and at times life-threatening. Ticlopidine-induced neutropenia has been described in patients receiving the medication. We report neutropenia occurring 18 days after discontinuation of ticlopidine. CONCLUSIONS: Indications for prescribing ticlopidine must be closely followed. Complete blood cell count monitoring is imperative while the patient is receiving the medication. This case suggests that the duration of monitoring after the discontinuation of ticlopidine may need to be longer than the 14 days recommended by the manufacturer.

Aged↗
PubMed1994

A simple dot-immunobinding assay for quantification of synaptophysin-like immunoreactivity in human brain.

Neocortical decreases in synaptic density correlate significantly with the cognitive impairment seen in Alzheimer disease. Recently available monoclonal antibodies (MAb) have made possible the highly specific and sensitive detection of synapse-associated proteins in immunocytochemical and immunochemical techniques. We describe a simple yet highly sensitive dot-immunobinding assay for relative quantification of the synapse marker protein synaptophysin in human brain homogenate fractions with the mouse MAb SY38. Fractions prepared from control and Alzheimer specimens were blotted to nitrocellulose membranes and reacted with SY38, rabbit secondary antibody, and iodinated protein A. A relative standard curve was constructed to normalize results from multiple assay runs. We correlated the results with the more complex immunocytochemical synaptic density measurement technique of immunolabeling coupled with laser confocal imaging, showing good correlation at r = 0.821. Results from Alzheimer cases showed a 40% decrease in synaptophysin immunoreactivity in midfrontal cortex compared with normal controls.

Aged↗
PubMed1993

Multifocal necrotizing leukoencephalopathy with pontine predilection in immunosuppressed patients: a clinicopathologic review of 16 cases.

Multifocal necrotizing leukoencephalopathy (MNL) is characterized by multiple, usually microscopic, foci of necrosis confined primarily to the white matter of the basis pontis, but sometimes found elsewhere in the central nervous system. All 16 patients in whom we identified MNL had underlying immunosuppression, either naturally occurring or iatrogenic, including the acquired immunodeficiency syndrome (seven patients), acute leukemias (four patients), and lymphoma (one patient). One patient each had severe combined immunodeficiency, orthotopic liver transplantation, Shwachman-Diamond syndrome, and idiopathic thrombocytopenic purpura treated with high-dose steroids. Histologically, lesions of MNL show demyelination, spongiosis, axonal swelling, minimal histiocytic infiltrates, and frequent axonal calcification. Multifocal necrotizing leukoencephalopathy lesions were found in the pons of all patients, most commonly in the crossing pontocerebellar fibers, but often in the descending white matter tracts and rarely in the tegmentum. Three cases also showed nonpontine foci of MNL involving the white matter of the medulla, cerebellum, and cerebral hemispheres. Multifocal necrotizing leukoencephalopathy is a distinct entity usually localized to the basis pontis and is most consistently associated with immunosuppression, but as yet lacks other clearly defined clinical correlates.

Adult↗
PubMed1993

Plaque-only Alzheimer disease is usually the lewy body variant, and vice versa.

A minority of neuropathologically confirmed Alzheimer disease (AD) brains lack neocortical neurofibrillary tangles or have very few, constituting a form of "plaque-only AD." A significant percentage of clinically diagnosed AD patients are found at autopsy to have both AD and brainstem and neocortical Lewy bodies. Many of these Lewy body variants of AD (LBV) have numerous senile plaques but no neocortical neurofibrillary tangles, and so resemble plaque-only AD. In this study, we sought to determine if plaque-only AD was usually LBV, and, conversely, if LBV was usually plaque-only AD. We analyzed 147 consecutively accessioned cases of neuropathologically confirmed AD, diagnosed according to criteria from the National Institute on Aging and the Consortium to Establish a Registry for Alzheimer's Disease. Twenty-five percent of all AD cases in this series were plaque-only AD, and 75% were plaque and tangle AD. Twenty-eight percent of AD cases in this series were LBV, and 72% were pure AD. Of the plaque-only AD cases, 75% were LBV and only 25% were pure AD. Of the LBV, 66% were plaque-only AD and only 33% were plaque and tangle AD. These results indicate that most plaque-only AD is LBV, and, conversely, that most LBV is plaque-only AD.

Aged↗
PubMed1993

Immunoreactivity of the nuclear antigen p105 is associated with plaques and tangles in Alzheimer's disease.

BACKGROUND: The protein p105 is a nuclear antigen associated with cell proliferation. Recent investigations have indicated that many molecules previously considered to be growth-associated are actually involved in plasticity of the central nervous system. EXPERIMENTAL DESIGN: For the present study, using immunohistochemical and immunochemical techniques in control and Alzheimer's disease (AD) brain, we explored the possibility that p105 could be involved in the aberrant sprouting response. AD tissue was used because in this disorder, the neuronal sprouting processes display a disruption in their cytoskeleton and the microtubule-associated protein, tau is abnormally phosphorylated. Control experiments were performed with the p105 antibody from an independent source, and with an antibody against Ki-67. RESULTS: The antibody against p105 (but not against Ki-67) immunolabeled the tangles, neuropil threads, and a subpopulation of fusiform neurites in the plaque. The p105 immunoreactivity was colocalized with tau and the numbers of tangles immunostained with p105 antibody correlated with the number of tangles immunolabeled with an antibody against tau. Western blot analysis of human brain homogenates showed that the antibody against p105 immunostained a major band at an estimated molecular weight of 105 kilodaltons and a secondary band at 84 kilodaltons. In AD frontal cortex, there was a significant increase in the 84 kilodalton band in the particulate, but not in the cytosolic fraction. CONCLUSIONS: The characterization of the patterns of expression of this class of nuclear antigen in the brain might provide important clues as to the mechanisms of plasticity and abnormal growth under normal conditions, as well as in AD.

Aged↗
PubMed1992

Casein kinase II is associated with neurofibrillary tangles but is not an intrinsic component of paired helical filaments.

Neurofibrillary tangles (NFT) are pathological cytoskeletal structures composed of paired helical filaments (PHF), and are found in neurons of patients afflicted with many neurodegenerative disorders, including Alzheimer's disease (AD). We previously found that an antiserum against casein kinase II (CK-II) stained NFT intensely in the brain tissue of AD patients. In the current study, we found that the anti-CK-II antiserum stains NFT and neuronal inclusions in many other neurodegenerative diseases as well, including Guam-Parkinson dementia complex, chromosome 18 deletion syndrome, progressive supranuclear palsy, Kufs' disease, and Pick's disease. This antiserum reacted, in crude brain homogenates, with both a doublet of Mr 43,000 and a Mr 27,000 Da protein which could correspond to the alpha, alpha', and beta chains of CK-II. The staining of these bands was adsorbed by preincubating anti-CK-II antiserum with purified CK-II. Preincubation of brain sections with purified CK-II strongly intensified the immunostaining of NFT with anti-CK-II, suggesting that NFT may bind CK-II. In the AD brain homogenates, the particulate CK-II levels are increased whereas the cytosolic levels are decreased without a change in total CK-II levels, consistent with the idea that CK-II binds to the particulate PHF, a major constituent of NFT. In accord with these findings, purified PHF bound CK-II, but purified PHF did not contain CK-II as its component. These results suggest that CK-II might be an extraneously deposited component of NFT. Thus, the altered CK-II compartmentalization might have significant consequences in the pathogenesis of AD.

Brain↗
PubMed1992

Serological alpha 1-antichymotrypsin in Down's syndrome and Alzheimer's disease.

alpha 1-Antichymotrypsin (ACT) is a serine protease inhibitor that is markedly elevated in the serum and cerebrospinal fluid of patients with Alzheimer's disease (AD). Patients with Down's syndrome are known to develop neuropathological changes of AD by age 40 years and many become demented. Therefore, in the present study, we obtained serum ACT levels from patients with Down's syndrome and AD, diagnosed by autopsy or clinically, and healthy control subjects. Newman-Keuls' multiple range test revealed a significantly greater (p less than 0.01) mean ACT level in the Autopsy AD (906.4 +/- 94.64 mg/L) and Clinical AD (745.00 +/- 59.95 mg/L) groups in contrast to the Old Control group (531.00 +/- 23.05 mg/L). The mean ACT level of the Down's Syndrome group (513.33 +/- 14.73 mg/L) was not significantly different from that of the Young Control subjects. Furthermore, we did not observe a positive correlation of ACT levels with age in the Down's Syndrome group, in spite of the age-dependent premature increase in neuropathological changes of AD that are known to occur in patients with Down's syndrome. A positive correlation between serum ACT levels and the density of plaques or tangles, neuropathological hallmarks of AD, in brains of patients with AD also did not exist. Thus, our results suggest that ACT levels may not parallel the development of the classical neuropathological hallmarks of AD.

Adult↗
PubMed1992

Selective neuronal vulnerability in HIV encephalitis.

Recent studies of human immunodeficiency virus type 1 (HIV-1) encephalitis have shown that in addition to well established white matter damage, the neocortex shows thinning, loss of large neurons and dendritic damage. In order to identify neuronal populations affected in HIV encephalitis and to determine how neuronal damage relates to the severity of HIV infection within the nervous system, we quantified parvalbumin (PV+) and neurofilament (NF+) immunoreactive neurons in the frontal cortex and hippocampus. We found that in the neocortex, the density of NF+ and PV+ neurons was independent of severity of HIV encephalitis, and therefore changes in these neuronal subsets did not account for previously reported neuronal loss. However, neuritic processes of PV+ neurons were fragmented, atrophic and in some cases distended. In contrast to the frontal cortex, there was a trend toward decreased density of PV+ neurons in the hippocampus which only reached significance in the CA3 layer where there was a 50-90% decrease in PV+ neurons. This decrease was closely correlated with the severity of HIV encephalitis. Double-label immunocytochemical analysis confirmed neuritic damage to interneurons. These results suggest that HIV encephalitis differentially involves specific subpopulations of neurons. Since direct HIV infection of neuronal cells was not detected, damage to PV+ cells and fibers may be indirectly mediated by cytokines released by HIV-infected microglia.

AIDS Dementia Complex↗
PubMed1992

Gallium nitrate.

OBJECTIVE: To evaluate the therapeutic role of gallium nitrate in the treatment of hypercalcemia associated with malignancy and related disease states. DATA SOURCES: A literature search of English-language studies involving gallium nitrate for the period 1966-1991 using MEDLINE and the bibliographies of relevant articles. STUDY SELECTION: Because of the limited number of studies, all clinical trials were reviewed, with particular emphasis on Phase III comparative trials. Related investigative studies on the pharmacology, pharmacokinetics, and toxicity of gallium nitrate were also reviewed. DATA EXTRACTION: Two appraisers independently abstracted data from available clinical trials and evaluated trial quality. RESULTS OF DATA SYNTHESIS: Two Phase III comparative trials evaluating gallium nitrate in the treatment of hypercalcemia of malignancy have been completed. Gallium nitrate was shown to be superior to both calcitonin and etidronate disodium, based on the comparative percentage of patients achieving normocalcemia and the subsequent duration of normocalcemia. Both trials employed similar methodology. Positive therapeutic effects of gallium nitrate have also been demonstrated in small, noncomparative trials for hypercalcemia associated with parathyroid carcinoma, Paget's disease of bone, and osteolytic bone metastases. CONCLUSIONS: Gallium nitrate is effective in the treatment of hypercalcemia associated with malignancy and is appropriate for formulary addition. In certain clinical situations, it may be clearly advantageous over such agents as calcitonin, plicamycin, and etidronate. Further investigation is needed to define the limitations of nephrotoxicity and the therapeutic potential for other indications. Further comparative clinical trials of gallium nitrate versus bisphosphonates and plicamycin could also help define its relative clinical benefit.

Gallium↗