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S Falk

Publications and source records attributed to S Falk.

At least 37 records · Page 2Linked to original sources
PubMed1999

Hemolysate-mediated renal vasoconstriction and hypersensitization.

The present studies measured vessel diameter, before and after addition of hemolysate, in isolated afferent arterioles (AA) and efferent arterioles (EA) obtained from the rat kidney. Human red blood cells (RBC) were hemolyzed in distilled water and membranes were discarded after centrifugation. Hemolysate added to the bath solution caused vigorous AA and EA contraction and, after washout, hypersensitized the AA and EA to doses of angiotensin II (AII) which would normally only elicit 50% contraction (EC50). Neither the contraction nor the hypersensitization were mimicked by pure human hemoglobin. The vasoconstrictive responses in the AA and EA were accompanied by increased cytosolic-free calcium concentration. Further purification (desalting) of the hemolysate to remove substance of < or = 1000 Da (which include ATP) did not eliminate the vasoconstrictive component from the hemolysate. Finally, cultured rat aortic vascular smooth muscle cells also demonstrated a rapid increase in (Ca2+i) when exposed to hemolysate. This increase in (Ca2+i) was, in part, dependent on Ca2+ influx since it could be attenuated with diltiazem (10(-5) M). In conclusion, hemolysate contains a factor which induces contractions of the isolated rat kidney AA and EA and rapid elevations in (Ca2+i). This factor, from hemolyzed RBC, is not hemoglobin itself.

Animals↗
PubMed1998

Reduction of an eight-state mechanism of cotransport to a six-state model using a new computer program.

A computer program was developed to allow easy derivation of steady-state velocity and binding equations for multireactant mechanisms including or without rapid equilibrium segments. Its usefulness is illustrated by deriving the rate equation of the most general sequential iso ordered ter ter mechanism of cotransport in which two Na+ ions bind first to the carrier and mirror symmetry is assumed. It is demonstrated that this mechanism cannot be easily reduced to a previously proposed six-state model of Na+-D-glucose cotransport, which also includes a number of implicit assumptions. In fact, the latter model may only be valid over a restricted range of Na+ concentrations or when assuming very strong positive cooperativity for Na+ binding to the glucose symporter within a rapid equilibrium segment. We thus propose an equivalent eight-state model in which the concept of positive cooperativity is best explained within the framework of a polymeric structure of the transport protein involving a minimum number of two transport-competent and identical subunits. This model also includes an obligatory slow isomerization step between the Na+ and glucose-binding sequences, the nature of which might reflect the presence of functionally asymmetrical subunits.

Biological Transport↗
PubMed1998

Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial.

OBJECTIVE: To test if supplemental dietary selenium is associated with changes in the incidence of prostate cancer. PATIENTS AND METHOD: A total of 974 men with a history of either a basal cell or squamous cell carcinoma were randomized to either a daily supplement of 200 microg of selenium or a placebo. Patients were treated for a mean of 4.5 years and followed for a mean of 6.5 years. RESULTS: Selenium treatment was associated with a significant (63%) reduction in the secondary endpoint of prostate cancer incidence during 1983-93. There were 13 prostate cancer cases in the selenium-treated group and 35 cases in the placebo group (relative risk, RR=0.37, P=0.002). Restricting the analysis to the 843 patients with initially normal levels of prostate-specific antigen (< or = 4 ng/mL), only four cases were diagnosed in the selenium-treated group and 16 cases were diagnosed in the placebo group after a 2 year treatment lag, (RR=0.26 P=0.009). There were significant health benefits also for the other secondary endpoints of total cancer mortality, and the incidence of total, lung and colorectal cancer. There was no significant change in incidence for the primary endpoints of basal and squamous cell carcinoma of the skin. In light of these results, the 'blinded' phase of this trial was stopped early. CONCLUSIONS: Although selenium shows no protective effects against the primary endpoint of squamous and basal cell carcinomas of the skin, the selenium-treated group had substantial reductions in the incidence of prostate cancer, and total cancer incidence and mortality that demand further evaluation in well-controlled prevention trials.

Basal Cell Carcinoma↗
PubMed1998

Deciding about hormone therapy: validation of a model.

OBJECTIVE: The purposes of this study were to (1) validate components of a decision process regarding adoption of hormone therapy and (2) compare the decision processes women used with respect to their evaluation of decision quality. DESIGN: A sample of women participating in a population-based study of midlife women's health participated in individual in-depth interviews. RESULTS: Content analysis of 30 recorded interviews provided evidence that each component of the decision process (precontemplation, contemplation, commitment, critical evaluation, and continuance) was replicated. Few additional codes were identified, and these could be subsumed under the phases of the original decision model. CONCLUSIONS: Women's self-reported statuses on a screening questionnaire corresponded to the stages of the decision model coded from their interviews. What women actually decided to do (use hormone therapy or something else) was not associated with their decision process. Satisfaction with the decision, uncertainty about the decision, and other factors related to the decision were independent of the decision phases.

Adult↗
PubMed1996

[Metastatic malignant melanoma in treated non-Hodgkin's lymphoma].

Secondary cutaneous neoplasia, e.g. basal cell malignant carcinomas or squamous cell carcinomas, is frequently observed in patients with malignant lymphomas. The association between malignant lymphoma and secondary malignant melanoma has only been rarely reported. We describe a patient with a low-grade nodal B-cell lymphoma who, while on treatment with steroids and an alkylating agent, developed a malignant melanoma level IV which rapidly metastasized to lymph nodes involved by the malignant lymphoma.

Adult↗
PubMed1996

[Axillary silicon lymphadenopathy after breast augmentation].

We report on a case of axillary lymphadenopathy in a 40-year-old woman secondary to a bilateral silicone augmentation mammoplasty which occurred 10 years after surgery. Microscopic silicone leakage ("bleeding") from an intact prothesis lead to sizeable lymph node enlargement. The suspected malignant tumour (metastasis/malignant lymphoma) could be ruled out by histological examination of the lymph node.

Adult↗
PubMed1994

Characterization of the beta 2-microglobulin endocytic pathway in rat proximal tubule cells.

The uptake mechanism(s) of low-molecular-weight proteins by proximal tubule cells remains incompletely characterized. We utilized a biochemical and semiquantitative morphological approach to better characterize the endocytic pathway of an anionic protein, beta 2-microglobulin (beta 2M), in the rat proximal tubule. Indirect immunogold techniques revealed beta 2M was taken up via a classic receptor-mediated endocytic pathway. In vitro biochemical and morphological characterization of iodinated beta 2M and gold-conjugated beta 2M (gold-beta 2M) binding to isolated brush-border membrane vesicles (BBMV) documented specific and quantitatively similar binding interactions of the modified beta 2M with BBMV. Kinetic characterization of the in vivo endocytic pathway of gold-beta 2M was undertaken using microinfusion of individual tubules. beta 2M initially bound at the apical surface, was internalized into subapical coated vesicles and delivered to endosomal-like structures within 5 min, and, finally, was concentrated in lysosomal-like structures within 15 min. This uptake was inhibited by excess unconjugated beta 2M. In addition, we directly showed that uptake did not occur across the basolateral surface. Finally, by passing solubilized BBMV over beta 2M affinity columns we were able to isolate binding activity.

Animals↗
PubMed1993

Splenic haematopoiesis in primary (idiopathic) osteomyelofibrosis: immunohistochemical and morphometric evaluation of proliferative activity of erytro- and endoreduplicative capacity of megakaryopoiesis (PCNA- and Ki-67 staining).

Using monoclonal antibodies against proliferating cell nuclear antigen or PCNA (PC10) and the Ki-67 antigen (MIB1), an immunohistochemical and morphometric study was performed on routinely processed splenic tissue from ten patients with primary (idiopathic) osteomyelofibrosis (OMF). To determine the proliferation capacity of erythroid precursors and the endoreduplicative activity of megakaryocytes, corresponding antibodies (Ret40f and CD61) were applied in combination with the cell-cycle markers (sequential double-immunostaining). Morphometric analysis revealed no significant differences in PCNA or Ki-67 reactivity in either cell lineages. In comparison with previous studies on normal bone marrow, in splenic tissue showing myeloid metaplasia, the numbers of PCNA-labelled proerythroblasts, erythroblasts and megakaryocytes were conspicuously increased. Considering the ineffective erythropoiesis in OMF, there seemed to be a disproportional enhancement in PCNA and Ki-67 immunostaining of the red cell lineage. Similarly, the small size of megakaryocytes in advanced, OMF-associated myeloid metaplasia was in keeping with an impairment of endoreduplicative activity. In addition to various other contributory factors, anaemia in OMF may be partially caused by secondary folate (haematinic) deficiency. From experimental studies this defect is known to cause an abnormal arrest in the S-phase of the cell-cycle, comparable to that characterising pernicious anaemia. As a sequel of this pathomechanism, an undue overexpression of PCNA and Ki-67 has to be assumed, that is not necessarily associated with DNA synthesis or cell cycling.

Aged↗
PubMed1993

Primary angiosarcoma of the spleen. A clinicopathologic study of 40 cases.

Forty primary splenic angiosarcomas occurring in 21 men and 19 women, 19-84 years old (median 59 years) are reported. Patients presented with splenomegaly (35 of 38, 92%), abdominal pain (33 of 40, 83%), and systemic symptoms such as fatigue (2 of 40, 5%), fever (4 of 40, 10%), and/or weight loss (16 of 40, 40%). Five (13%) experienced splenic rupture associated with hemoperitoneum. Abnormal laboratory findings included cytopenia (31 of 34, 91%), leukocytosis (8 of 21, 38%), and thrombocytosis (1/39, 3%). Most spleens weighed 500-1,000 g (mean, 1,180 g). The cut splenic surfaces showed multiple hemorrhagic nodules that were frequently associated with infarction, although some had a diffuse pattern of involvement. Microscopically, there were a variety of histologic patterns displayed by the vasoformative component. A honeycomb or sponge-like pattern was common in some, whereas others simulated a cavernous hemangioma or normal splenic sinuses (pseudosinusoidal pattern). Papillary endothelial tufts and solid proliferations of spindled to round to epithelioid cells were also seen. Factor VIII-related antigen was detected in 19 of 23 cases, BMA-120 in 18 of 23, UEA-1 receptor in 18 of 23, and vimentin in 23 of 23 as well as CD68 antigen in 1 of 23 cases. S-100 protein and cytokeratin were not found in any of the 23 cases studied. Metastases in 22 of 32 patients (69%) were to the liver (13 patients), bone or bone marrow (7 patients), lymph nodes (1 patient), and brain (1 patient). Three patients had concomitant malignancies and one had a prior history of a mixed B-cell lymphoma 5 years previously that had been treated with chemotherapy. Follow-up in 38 patients revealed that 30 (79%) are dead at a median interval of 6 months (range 0-48 months) and 8 are alive 5-21 months after diagnosis. These findings indicate that splenic angiosarcoma is an aggressive neoplasm with a high metastatic rate and an abysmal prognosis. Recognition of the wide range of histologic patterns is of diagnostic value but no apparent prognostic significance.

Adult↗
PubMed1992

In vitro culture of common acute lymphoblastic leukemia blasts: effects of interleukin-3, interleukin-7, and accessory cells.

We investigated the effects of interleukin-3 (IL-3), IL-7, IL-1, and IL-6, of irradiated bone marrow-derived fibroblasts (Fb) and of in vitro matured peripheral blood macrophages (M phi), on the survival, proliferation, and maturation of purified blasts from nine common acute lymphoblastic leukemias (cALLs) in 7-day suspension culture. Exposure to IL-3, IL-7, IL-1, and IL-6 resulted in a mean 2.8-, 1.5-, 1.4-, and 1.6-fold stimulation of 3H-thymidine (3H-TdR) incorporation, respectively. Cocultures of cALL blasts with irradiated M phi, either allowing direct cell-cell contact or preventing it by membrane filters, or with irradiated Fb, resulted in a mean 31.7-, 4.1-, and 11.2-fold increase of 3H-TdR incorporation, respectively. Southern blot analysis of immunoglobulin and T-cell receptor (TCR) gene rearrangements before and after culture indicated exclusive proliferation of the leukemic clone in three of eight samples, whereas additional generation of nonleukemic cells was found in five samples. Polyclonal growth pattern corresponded to the detection of heterogeneous cell populations using FACS analysis. Survival of cALL blasts as defined by the detection of cells coexpressing both CD10 and CD19 after culture was supported by accessory cells in five of eight samples. No evidence of induced lymphoid maturation was found under any culture condition. Our data demonstrate supportive effects of stromal cells on cALL growth, which cannot be replaced by IL-3 or IL-7.

Blotting, Southern↗
PubMed1992

[Spontaneous splenic rupture in acute malaria tropica].

A 44-year-old man developed bouts of fever (up to 40 degrees C) seven days after returning from a holiday in Kenya. Malaria prophylaxis with chloroquine had been correctly undertaken. Concentrations of lactate dehydrogenase and total bilirubin were raised (493 U/l and 3.55 mg/dl, respectively). Blood smear revealed the ring forms of Plasmodium falciparum. Thereupon the patient was given mefloquine in decreasing doses (750/500/250 mg) at intervals of 8 hours. The following night he had a circulatory collapse and complained of pain on pressure, especially in the left upper abdomen. Abdominal sonography showed a slightly enlarged spherical spleen with an echo-poor band and fluid collection in the rectovesicular pouch, indicating rupture of the spleen. A splenectomy was performed. Subsequently the number of malaria organisms in the blood smear gradually fell and signs of haemolysis disappeared. Splenic rupture is a very rare complication of acute malaria. It is presumably caused by marked stasis in the splenic sinuses with deformed parasite-containing red blood cells.

Acute Disease↗
PubMed1992

Primary large cell lymphoma of the splenic sinuses: a variant of angiotropic B-cell lymphoma (neoplastic angioendotheliomatosis)?

A case of large cell lymphoma of B-cell lineage originating in the splenic sinuses is described. In addition to widening the spectrum of primary malignant lymphomas of the spleen, this case raises the possibility that variants of angiotropic large cell lymphomas may exist that do not involve blood vessels but do involve the spleen and lymph node sinuses.

Aged↗
PubMed1992

Splenic megakaryocytopoiesis in primary (idiopathic) osteomyelofibrosis. An immunohistological and morphometric study with comparison of corresponding bone marrow features.

An immunohistochemical and morphometric study has been performed on splenic tissue of 10 patients with primary (idiopathic) osteomyelofibrosis (OMF) to determine characteristic features of megakaryocytopoiesis in myeloid metaplasia. Using the periodic acid-Schiff reaction (PAS) and particularly the monoclonal antibody CD61 (Y2/51), all elements of this cell lineage including precursors could be identified. In comparison with bone marrow specimens from our file material (40 patients with OMF, 15 control cases) which were processed in a similar way, megakaryocytes in the spleen revealed significant differences. These differences included smaller cell sizes, a disturbed nuclear-cytoplasmic ratio, and a conspicuous increase in the relative frequency of promegakaryoblasts. In conclusion, extramedullary megakaryocytopoiesis in OMF did not only show more pronounced abnormalities of differentiation, but also a higher degree of immaturity. Our finding of a significant accumulation of megakaryocytic precursors in the spleen as opposed to the bone marrow, corroborates the so-called filtration theory which has been introduced to explain the evolution of splenic myeloid metaplasia in OMF.

Aged↗