Biomedical subjects

P A Lowry

Publications and source records attributed to P A Lowry.

At least 19 recordsLinked to original sources

PubMed2006

Pathological effects of alcohol septal ablation for hypertrophic obstructive cardiomyopathy.

BACKGROUND: The pathological effects and the mechanisms of action of intracoronary administration of ethanol for alcohol septal ablation (ASA) for the management of hypertrophic obstructive cardiomyopathy (HOCM) are unknown. METHODS: We examined surgical specimens and, in one case, autopsy specimens from four patients who underwent surgical septal myectomy 2 days to 14 months after unsuccessful ASA. RESULTS: Pathological examination early after ASA showed coagulative necrosis of both the myocardium and the septal perforator arteries. Affected arteries were distended and occluded by necrotic intraluminal debris, without platelet-fibrin thrombi. Late after unsuccessful ASA, excised septal tissue was heterogeneous, containing a region of dense scar, and adjacent tissue containing viable myocytes and interspersed scar. CONCLUSIONS: Intracoronary administration of ethanol in patients with HOCM causes acute myocardial infarction with vascular necrosis. The coagulative necrosis of the arteries, their distension by necrotic debris and the absence of platelet-fibrin thrombi distinguish ethanol-induced infarction from that caused by atherosclerotic coronary artery disease. The direct vascular toxicity of ethanol may be an important aspect of the mechanism of successful ASA.

Adolescent↗

PubMed1997

Occult trauma mimicking metastases on bone scans in pediatric oncology patients.

BACKGROUND: Tracer-avid osseous lesions are usually considered to represent metastases in pediatric oncology patients. However, sites of minor, clinically occult, skeletal trauma may be mistaken for osseous metastases. OBJECTIVE: The objective of this study was to review our experience with skeletal scintigraphy in pediatric oncology patients to determine specificity for metastatic disease. Materials and methods. We reviewed 164 bone scans performed on 96 consecutive patients (ages 5 months to 23 years) at presentation with malignancy or during chemotherapy. Tumors included osteosarcoma (13), Ewing sarcoma (11), lymphoma (19), neuroblastoma (12), brain tumors (16), rhabdomyosarcoma (10), renal tumors (5), and miscellaneous neoplasms (10). Scintigraphic abnormalities were considered metastatic based on radiographic findings, subsequent tumor progression, or multiplicity of lesions. Lesions were considered benign when spontaneous resolution occurred without change in therapy or radiographs demonstrated a traumatic or other benign lesion. RESULTS: Of the 96 patients, 51 had normal studies or showed only the primary lesion. Of the 45 patients with abnormal scintigraphy, 16 (35 %) had metastases and 29 (65 %) had one or more focal benign lesions. These lesions included abnormalities due to stress/trauma (25), benign neoplasm (2), infection (3), disuse (6), surgery (10) and artifacts (4). CONCLUSION: The majority of scintigraphic abnormalities have nonmalignant etiologies, most commonly stress reaction and trauma. In patients without known extraosseous metastases, one or two skeletal lesions should not be assumed to represent metastatic disease.

Adolescent↗

PubMed1997

Spontaneous splenic rupture following administration of granulocyte colony-stimulating factor (G-CSF): occurrence in an allogeneic donor of peripheral blood stem cells.

Granulocyte colony-stimulating factor (G-CSF) has been used to improve granulocyte count in chronic neutropenia and myelodysplasia, to minimize the incidence and duration of neutropenia during conventional chemotherapy, and to mobilize peripheral blood stem cells prior to leukapheresis for use in autologous and allogeneic marrow transplantation. The most common toxicity is bone pain, and other reactions such as inflammation at the site of injection have also occurred. In patients with chronic neutropenia, splenomegaly has been described with long-term use, and extramedullary hematopoiesis has also been reported. However, thus far, no life-threatening sequelae of these effects are found in the literature. We now describe a case of spontaneous splenic rupture four days following a six-day course of G-CSF therapy in an allogeneic donor of peripheral blood stem cells.

Acute Disease↗

PubMed1997

Renal neoplasms of childhood.

Wilms' tumor is the most common childhood renal tumor. This article describes the epidemiology, histopathologic features, and clinical manifestations of Wilms' tumor along with the spectrum of imaging findings using different modalities. The distinguishing features of other renal tumors encountered in children, such as clear cell sarcoma, rhabdoid tumor, congenital mesoblastic nephroma, multilocular cystic renal tumor, renal cell carcinoma, and angiomyolipoma are also reviewed.

Child↗

PubMed1996

Clinical challenges and cord blood transplantation: are we asking the right questions?

Cord blood offers an exciting alternative to traditional sources of stem cells for clinical transplantation, but its use will test traditional limits on minimal cell numbers required for engraftment as well as other aspects of the stem cell model of hematopoiesis. There is great interest in stem cell selection and ex vivo expansion techniques as they apply to cord blood. Although provocative, these approaches in their emphasis on the quantitative should not be allowed to obscure the important qualitative differences of cord blood with respect both to hematopoietic reconstitution per se and in the larger context to the unique immunologic status of that product. Whereas the momentum of cord blood transplantation may arise from the explosion in animal model-based stem cell biology, its direction must be determined by the clinical end points we week.

Animals↗

PubMed1996

Hematopoietic "stem cell" transplantation: are there any clouds on an expanding horizon?

Clinicians contemplating stem cell transplantation for the treatment of their patients are faced with an increasing number and complexity of options for the source of the stem cells and their manipulation prior to transplant. Many of these strategies focus on the traditional concept of the "hematopoietic stem cell" as a unitary and independent source of reconstitution. Evolving animal studies suggest that the stem cell concept is incompletely defined and that the stem cell compartment retains significant heterogeneity of function. These findings should be combined with the increasingly heterogeneous goals of stem cell transplantation to induce caution in proceeding forward with new technologies.

Animals↗

PubMed1996

Improved engraftment of human cord blood stem cells in NOD/LtSz-scid/scid mice after irradiation or multiple-day injections into unirradiated recipients.

Human lymphoematopoietic stem cells engraft in irradiated immunodeficient mice that are homozygous for the severe combined immunodeficiency (scid) mutation. Engraftment levels in C.B-17-scid/scid mice, however, have been low and transient, decreasing the utility of this model for investigation of the development potential and function of human stem cells. In the present study, we have used NOD/LtSz-scid/scid mice as recipients and human cord blood as a source of donor stem cells. Our results demonstrate that NOD/LtSz-scid/scid mice support approximately fivefold higher levels of human stem cell marrow engraftment than do C.B-17-scid/scid mice. Human CD34+ cells are present in the marrow of recipient mice, and the engrafted cells readily peripheralize to the circulation of the host. Terminal differentiation of the stem and progenitor cells into mature progeny is limited. Using a multiple-day injection protocol developed in mice, which allows engraftment of stem cells between congenic mice in the absence of irradiation preconditioning, we observed high levels of human cell engraftment in unirradiated NOD/LtSz-scid/scid recipients after three or five consecutive-day injections. These results demonstrate that NOD/LtSz-scid/scid mice support high levels of human stem cell engraftment and that xenogeneic lymphohematopoietic stem cells can engraft in unirradiated hosts without the need for ablative reconditioning. This model will be useful for the in vivo investigation of human stem cells and for the preclinical analysis of human stem cells for transplantation.

Animals↗

PubMed1995

Hematopoietic stem cell cytokine response.

The process of hematopoiesis can be modelled on the concept of a pluripotential stem cell able to differentiate and proliferate in multiple lineages. This process proceeds under the permissive or directive influence of "early" and "late" acting hematopoietic cytokines probably acting in synergistic combinations within the context of the marrow stromal microenvironment. Further characterization of the biochemical events that transduce cytokine signalling into cellular events and the ultimate description of the earliest progenitor cell populations and the cytokines which influence them will provide key insights into embryogenesis and tissue maintenance as well as suggest new therapeutic approaches for hematologic and malignant diseases.

Animals↗

PubMed1995

Intense gallbladder uptake associated with chemotherapy. An unusual finding in pediatric skeletal scintigraphy.

Focal and diffuse hepatic uptake of bone-seeking radiopharmaceuticals may be due to a variety of conditions including tumors and radiopharmaceutical impurity. However, uptake in the gallbladder is unusual with currently used skeletal agents. Three patients (aged 10, 15, and 16 years) underwent routine whole-body bone scans during a course of intensive chemotherapy with VP-16 and ifosphamide. Images showed intense gallbladder and faint liver uptake. No patient had symptoms of cholecystitis. Radiopharmaceutical quality control revealed no impurities. Repeat bone scans after completion of chemotherapy showed no liver or gallbladder uptake. The authors conclude that this finding represents altered distribution induced by the chemotherapy regimen, and should not be misinterpreted as intrinsic liver or gallbladder disease.

Adolescent↗

PubMed1995

Comparison of gadolinium-enhanced MR and thallium-201 single photon emission computed tomography in pediatric brain tumors.

Despite its usefulness in adults with cerebral gliomas, indications for thallium-201 single-photon emission computed tomography (SPECT) in pediatric brain tumor patients are not well defined. We prospectively compared thallium SPECT with gadolinium-enhanced MR (Gd-MR) to determine if thallium SPECT provides clinically useful information that cannot be derived from Gd-MR. We studied 24 pediatric brain tumor patients, 7 at presentation and 17 during therapy. MR imaging included T2 and pre- and postgadolinium T1 images. Thallium SPECT was done within 48 h of MR imaging; thallium indices were calculated for 12 of 14 lesions which showed thallium uptake. Surgery and/or clinical follow-up are available in all patients. The tumors included pilocytic astrocytoma (7), medulloblastoma (5), brainstem glioma or glioblastoma (4), germinoma (3), optic glioma (2), mixed glioma (1), primitive neuroectodermal tumor (1), and choroid plexus carcinoma (1). Among the primary tumors, compared to MR, thallium SPECT was false-negative for tumor in 1 patient and true-positive in 6 patients. Among the patients studied while on therapy, compared to MR, thallium SPECT was true-negative for tumor in 7, true-positive in 5, false-negative in 3, and false-positive in 2. In both groups of patients, thallium SPECT underestimated tumor burden as nonenhancing regions of the tumors were not thallium-avid. Thallium indices did not correlate with histologic grade, biologic aggressiveness, or tumor type. We were unable to establish indications for the use of thallium SPECT in this setting as there was little clinically useful information derived from thallium SPECT that was not provided by Gd-MR.

Adolescent↗

PubMed1995

The high-proliferative-potential megakaryocyte mixed (HPP-Meg-Mix) cell: a trilineage murine hematopoietic progenitor with multiple growth factor responsiveness.

Megakaryocyte progenitors are notable for their response to synergistic cytokine combinations and apparently early position in the hematopoietic differentiation pathway. Although high-proliferative-potential murine megakaryocyte progenitors have been described, they have previously been primarily observed as unilineage colonies. We describe a subclass of agar-based high-proliferative-potential colony forming cells (HPP-CFC) derived from populations enriched for early hematopoietic progenitors which, when stimulated with the combination of CSF-1, G-CSF, GM-CSF, IL-1 alpha, IL-3 and SCF, produces colonies with trilineage potential for macrophages, granulocytes, and megakaryocytes. The high proliferative potential megakaryocyte mixed (HPP-Meg-Mix) colony-forming cell is defined as a cell meeting traditional criteria for HPP-CFC but additionally containing 20 or more megakaryocytes per colony. The combination of high-proliferative-potential, multilineage differentiation, and megakaryocytic lineage capacity suggests that the HPP-Meg-Mix marks a very early hematopoietic progenitor cell.

Acetylcholinesterase↗

PubMed1993

Long-term engraftment of normal and post-5-fluorouracil murine marrow into normal nonmyeloablated mice.

We report the successful long-term engraftment of normal male donor bone marrow (BM) transfused into noncytoablated female mice, challenging the assumption that "niches" need to be created for marrow to engraft. We have used chromosomal banding and Southern blot analysis to identify transplanted male marrow cells, and shown the long-term stability of the chimeric marrows. Balb/C, BDF1, or CBA-J female hosts (no irradiation) received for 5 consecutive days 40 x 10(6) male cells (per day) of the same strain, and repopulation patterns were observed. Parallel studies were performed using tibia/femur equivalents of normal marrow or marrow from Balb/C mice pretreated 6 days previously with 150 mg/kg 5-fluorouracil (5-FU). Chromosome banding techniques showed that 5% to 46% of marrow cells were male 3 to 9 months posttransplant with normal donor marrow. Southern blot analysis, using the pY2 probe, showed continued engraftment at 21 to 25 months posttransplant, ranging from 15% to 42% male engrafted cells in marrow. Normal donor male marrow engrafted significantly better than 5-FU-pretreated male marrow as shown 1 to 12 months posttransplant in non-cytoablated female recipients. Percentages of male engrafted cells in BM ranged from 23% to 78% for recipients of normal donor marrow and from 0.1% to 39% for recipients of 5-FU marrow. Mean engraftment for 6 mice receiving normal marrow was 38%, whereas that for 6 mice receiving post-5-FU marrow was 8%, as assayed 1 to 3 months posttransplant. At 10 to 12 months, mean engraftment for the normal donor group was 46%, compared with 16% for the 5-FU group. The patterns of engraftment with normal and 5-FU marrow were similar for spleen and thymus. These results show that long-term chimerism can be established after transplantation of normal donor marrow to normal nonirradiated host mice and indicate that marrow spaces do not have to be created for successful engraftment. They suggest that transplanted marrow competes equally with host marrow for marrow space. Finally, these data show that post-5-FU Balb/C male marrow is markedly inferior in the repopulation of Balb/C female host marrow, spleen, and thymus, and suggest that this population of cells may not be the ideal population for gene transfer studies.

Animals↗

PubMed1993

Interleukin-3/erythropoietin fusion proteins: in vitro effects on hematopoietic cells.

Erythropoietin (Epo) acts synergistically with interleukin-3 (IL-3) to induce proliferation and differentiation of erythroid progenitors. This synergy occurs at IL-3 concentrations that have little or no effect alone. To determine whether optimal expansion of erythroid cells results when they are targeted by a molecule with both IL-3 and Epo activities, fusion proteins were generated and analyzed. Expression vectors were constructed in which the coding regions of human IL-3 and Epo cDNAs were joined by either a short (2 to 3 amino acids) or long (23 amino acids) linker sequence and expressed in Chinese hamster ovary (CHO) cells. Analysis of equilibrium binding properties of the IL-3 and Epo moieties revealed that in all fusion proteins each retained the ability to bind receptor. When IL-3 was connected to Epo by a short linker, the binding affinity of the IL-3 moiety was lower. In vitro proliferative activity of each moiety was observed on cell lines responsive to IL-3, Epo or a combination of the two cytokines. Fusion of IL-3 to Epo through its amino terminus was found to result in partial loss of its function. All the fusion proteins were biologically active on human bone marrow. When IL-3 was located at the amino domain of the protein, induction of erythroid colonies was similar to that of a mixture of IL-3 and Epo. These results indicate that biological integrity of both IL-3 and Epo can be maintained when these cytokines are fused, but that enhancement of erythropoiesis over that observed with a mixture of the two cytokines cannot be achieved by their fusion alone. Other requirements such as the coexpression of the IL-3 and Epo receptors and the sharing of a receptor subunit are likely to be needed for an optimal cell response to the fusion growth factors.

Animals↗

PubMed1992

The colony-stimulating factors. An overview.

Hemopoietic cell proliferation, differentiation, and function appear to be regulated by cytokines designated as colony-stimulating factors (CSF) or interleukins (IL) based on their original description. These cytokines are characterized by pleiotropic actions in multiple lineages and at multiple levels. Additionally, synergistic interactions are prominent, particularly at the level of early stem cells. Baseline regulation of hemopoiesis may be regulated by presentation of multiple growth factors at the bone marrow stromal cell surface.

Animals↗

PubMed1992

Stem cell factor induction of in vitro murine hematopoietic colony formation by "subliminal" cytokine combinations: the role of "anchor factors".

The high levels of hematopoietic growth factors required for in vitro and in vivo activity raise questions as to their role in normal hematopoietic maintenance. We hypothesize that the use of combinations of cytokines to stimulate hematopoietic progenitors might allow individual factors to exert their influence at lower, more physiologically relevant concentrations. Growth factor combinations were assessed by their ability to stimulate both total colonies and high proliferative potential colony-forming cells (HPP-CFC), an early murine hematopoietic progenitor, in double-layer agar cultures. Very-low-level combinations of colony-stimulating factor (CSF)-1, granulocyte CSF (G-CSF), granulocyte-macrophage CSF (GM-CSF), interleukin (IL)-1 alpha, and IL-3 had little or no clonogenic capacity. Plateau levels of rr stem cell factor (rrSCF), a c-kit ligand, used alone also had negligible clonogenic capacity, but when combined with the low-level combination of the other five factors produced total colony and HPP-CFC growth approaching that produced by all factors at plateau levels. Delayed addition experiments suggest that this effect may represent sequential activity of SCF and the other factors. We propose a model of the normal hematopoietic microenvironment in which SCF at locally high concentration on the stromal cell surface "anchors" the hematopoietic stem cell's response to multiple other cytokines at physiologically relevant levels.

Animals↗

PubMed1992

Peripheral hematopoietic stem cell transplantation: current concepts.

As methods for increasing stem cells are perfected and alternate regimens for transplantation developed, PSCT will undoubtedly see wider application in combination with BMT and may ultimately replace BMT. The initial encouraging results with PSCT so far portend a major therapeutic role of this modality in the approach to hematologic and oncologic diseases. Prospective randomized trials comparing PSCT and BMT in a variety of clinical settings are needed and are already underway.

Blood Transfusion, Autologous↗

PubMed1992

Botanical musings.

Explore the source record for details and available documents.

Hematopoietic Stem Cells↗

PubMed1991

Delayed visualization of the gallbladder with a rim sign. An unusual finding in chronic cholecystitis.

The rim sign of increased activity in the gallbladder fossa during nuclear hepatobiliary imaging has been described, with one exception, only in conjunction with a nonvisualizing gallbladder, and it strongly suggests acute complicated cholecystitis. A case is presented in which a rim sign was present despite later visualization of the gallbladder in presumed chronic cholecystitis.

Adult↗