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Biomedical subjects

A Pollack

Publications and source records attributed to A Pollack.

At least 199 records · Page 11Linked to original sources
PubMed1990

Central neurofibromatosis: a clinical-pathological correlation.

Central neurofibromatosis is a genetic disorder of neural crest tissue derivatives that includes bilateral acoustic neuromas and other central nervous system tumors, usually meningiomas or gliomas. This is different from peripheral neurofibromatosis because of the primary central nervous system manifestations and frequent lack of accompanying peripheral neurofibromas and café au lait spots as well as different alterations of nerve growth factor. We present the temporal bone histopathology of a unique case of unsuspected central neurofibromatosis that included bilateral acoustic neuromas invading the cochlea and an asymptomatic glioblastoma multiforme occurring in the absence of a family history and without any accompanying peripheral stigmata of neurofibromatosis. As bilateral tumors frequently invade the cochlea, the modified transotic rather than the translabyrinthine approach is recommended for complete tumor removal. Contralateral tumor removal should be delayed while useful hearing remains.

Brain Neoplasms↗
PubMed1990

Repair of retinal pigment epithelium and its relationship with capillary endothelium after krypton laser photocoagulation.

The regeneration of the retinal pigment epithelial (RPE) cells and their relationship with the vascular endothelium were studied during the healing of laser burns produced by krypton laser photocoagulation in rats. During the healing process the epithelial sheet was reformed by a morphologically heterogeneous population of RPE cells, some of which resembled macrophages. There seems to be a correlation between the specific phenotype of the regenerated RPE cell and the state of vitality of the adjacent endothelium. This was particularly evident in the scattered foci of choroidal subretinal neovascularization surrounded by RPE cells. One possible explanation for this apparent correlation is that the cytologic variations of the RPE cells reflect the multiple functions of a single cell which is expressed differently in different situations and in the course of interaction with other cells. This presumed ability of RPE cells may explain an intriguing aspect of cell-cell interaction, namely, the dual stimulatory and inhibitory effects of RPE cells on the vascular endothelium.

Animals↗
PubMed1989

The fellow eye in retinal vein occlusive disease.

Bilateral occurrence of retinal vein occlusive disease is relatively uncommon. In this retrospective review of 157 patients with retinal vein occlusion, 74 had unilateral major trunk occlusion (MTO), i.e., either central (CRVO) or hemicentral (hemi-CRVO) retinal vein occlusion, 12 had MTO in both eyes, and two had MTO in one eye and branch retinal vein occlusion (BRVO) in the other. In 69 patients there was unilateral BRVO. Thus, 8.9% of the patients had bilateral retinal vein occlusive disease of any type. Of the 88 patients with MTO in at least one eye, 13.6% had MTO disease in the fellow eye as well and only 2.3% had BRVO in the fellow eye. Major trunk occlusion in one eye thus appears to be a greater risk factor than BRVO for the bilateral occurrence of retinal vein occlusive disease. Another factor predisposing to bilateral occurrence in the group of patients with MTO was the coexistence of diabetic retinopathy (P less than 0.05).

Age Factors↗
PubMed1988

Measurement of cell-cycle phase-specific cell death using Hoechst 33342 and propidium iodide: preservation by ethanol fixation.

We developed a rapid technique for preservation of Hoechst 33342/propidium iodide-stained cells, using ethanol as a fixative. Combined staining with these dyes makes possible analysis of cell-cycle phase-specific cell death. The technique relies on exclusion of propidium iodide from the viable cells, whereas Hoechst stains all of the cells. The bivariate histograms resulting from the flow cytometric analysis contain the equivalent of two single-parameter DNA histograms, one of the living and the other of the dead cell population. Preservation of staining involved addition of 25% ethanol in PBS after propidium iodide staining and before Hoechst staining. The separation between the living and the dead cell populations was maintained for over 3 days at 4 degrees C. This technique will be valuable for quantitative evaluation of the cell-cycle phase-specific effects of cytostatic or cytotoxic agents, particularly in situations where a lag period between staining and analysis is unavoidable.

Benzimidazoles↗
PubMed1987

In vivo cell kinetic effects of cis-platinum on human ovarian cancer xenografts measured by dual parameter flow cytometry.

Dual parameter flow cytometry, measuring DNA and nuclear protein of individual cell nuclei simultaneously, makes it possible to follow cell kinetic perturbations in six distinct compartments of the cell cycle following chemotherapy in vivo. Human ovarian cancer xenografts in nude mice from a primary and recurrent tumor of the same patient were studied. The response to intraperitoneal application of cis-platinum was assessed by tumor volume measurements, changes in labeling indices by autoradiography, and dual parameter flow cytometry. Sequential tissue samples were taken from each tumor using fine needle aspirations as a microbiopsy method. Pretherapy samples were compared to multiple specimens collected up to 18 days after therapy. Morphologic changes of each specimen were also assessed. Cis-platinum affects malignant cells in the G1B, S, G2A, and G2B compartments with various intensities and different time frames, depending on the drug sensitivity of each individual tumor.

Animals↗
PubMed1986

Ultrastructure of Bruch's membrane after krypton laser photocoagulation. I. Breakdown of Bruch's membrane.

Previous observations on rats suggested that subretinal neovascularization does not require a prior break in Bruch's membrane (BM). We verified this observation by using scanning electron microscopy to examine large expanses of BM that became exposed following ophthalmoscopically white krypton laser burns. Bruch's membrane appeared intact in the acute phase after injury. Subsequently, slitlike defects in BM were associated with penetrating choroidal capillaries. These observations were consistent with transmission electron microscopic findings of cellular protrusions arising from the choriocapillary endothelial cells and from regenerating retinal pigment epithelial (RPE) cells invading BM. These cell-formed defects in BM differed from thermal defects in appearance, size, and onset of occurrence. Endothelial cells penetrated all layers of BM, including the RPE basement membrane. We conclude that endothelial cells can erode their own basement membrane and the RPE basement membrane, and krypton laser burns with or without immediate rupture of BM induce cellular activity that may result in defects in BM.

Animals↗
PubMed1986

Ultrastructure of Bruch's membrane after krypton laser photocoagulation. II. Repair of Bruch's membrane and the role of macrophages.

The accompanying ultrastructural study showed that ophthalmoscopically white krypton laser photocoagulation in rats is followed by cellular invasion causing breakdown of Bruch's membrane (BM). We have expanded these observations, using scanning electron microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy to describe the healing process. The repair of BM involves regenerating retinal pigment epithelial cells and choriocapillaris (CC) that form new basement membranes and fibroblasts that secrete collagen and elastin. The reformation of the CC is also associated with subretinal neovascularization. The involvement of macrophages was evident throughout the process of BM repair and formation of new vessels. We propose that the macrophages act as a common factor linking the diverse diseases associated with choroidal subretinal neovascularization, deduced from our evaluation of the healing process and the reformation of choriocapillaris.

Animals↗
PubMed1986

In vivo chemosensitivity testing in patients with gynecologic malignancies and nude mouse xenografts by monitoring cell kinetic parameters and DNA distribution patterns: a preliminary report.

Using flow cytometry (FCM) and autoradiography we have evaluated changes in DNA-ploidy patterns as well as cell-cycle perturbations after chemotherapy in 12 patients with accessible tumors and 22 nude mice xenografts. Gynecologic malignancies growing as nude mouse xenografts serve as an experimental model to study the effect of chemotherapy at the cellular level. Excellent correlation was found between fine needle aspiration (FNA) and biopsy material for either FCM or autoradiography. It now appears possible to study the effects of chemotherapy in the patient as well as the animal model using serial FNAs as a microsampling technique.

Adenocarcinoma↗
PubMed1986

Cellular processes causing defects in Bruch's membrane following krypton laser photocoagulation.

Krypton laser photocoagulation of the posterior fundus of the rat created white retinal lesions comparable with therapeutic burns in the human. Twenty-four hours after injury, the retinal pigment epithelium was destroyed and the majority of the endothelial cells survived. The choriocapillary lumen was occluded. Bruch's membrane was not fractured nor had it undergone thermal lysis in any area studied but choriocapillary endothelial cell buds invaded the choroidal side of Bruch's membrane. After seven days, cellular protrusions arising from retinal pigment epithelial cells traversed Bruch's membrane through full-thickness defects and entered the choroid. Although intense laser burns may destroy Bruch's membrane, we conclude from this data that many so-called "breaks" in Bruch's membrane following laser therapy are formed by cellular processes and are not caused primarily by laser coagulation.

Animals↗
PubMed1986

High-voltage electron microscopy in eye research. Experimental analysis of the retinal pigment epithelium and choriocapillaris.

The high-voltage electron microscope (HVEM) permits examination of sections much thicker (up to 1 micron) than those usually used in transmission electron microscopy, which are approximately 70 nm in thickness. Two examples of the utility of the HVEM in research on the ultrastructure of the retinal pigment epithelium (RPE) and choriocapillaris are given: the identification of intracytoplasmic tubules that arise from the basal plasma membrane of rat RPE cells; and the tracing of processes arising from choriocapillary endothelial cells during experimentally induced neovascularization. In each case HVEM provided information not easily obtained in routine thin sections.

Animals↗
PubMed1985

Cell kinetic effects of incorporated 3H-thymidine on proliferating human lymphocytes: flow cytometric analysis using the DNA/nuclear protein method.

Phytohemagglutinin-stimulated human peripheral blood lymphocytes incorporating high concentrations of 3H-thymidine accumulate in G2 and show a consequent reduction in the number of cells entering M (division delay). The simultaneous flow cytometric analysis of DNA content (propidium iodide fluorescence) and nuclear protein content (fluorescein isothiocyanate fluorescence) allows for the accurate quantitation of these events; G2 and M are separated in the bivariate distributions. A good correlation was observed between mitotic indices, quantitated by manually counting mitotic cells, and integration of the M area in DNA/nuclear protein histograms. Moreover, significant differences in G2 nuclear protein levels were found between untreated and 3H-thymidine-treated lymphocytes. In order to characterize this effect, G2 was empirically divided into low nuclear protein (G2A) and high nuclear protein (G2B) compartments. 3H-thymidine caused an initial accumulation of lymphocytes in G2A, followed within 3-6 h by a gradual movement of some cells into G2B, with a subsequent accumulation of cells in G2B. The results suggest that the distribution of cells in G2 (G2A and G2B), the average nuclear protein content of G2B cells, and the proportion of cells in M are parameters that when used in combination provide a unique description of radiobiological effects.

Cell Cycle↗
PubMed1985

Tumor progression in serial passages of the Dunning R3327-G rat prostatic adenocarcinoma: growth rate response to endocrine manipulation.

Serial passages of the poorly differentiated, androgen-sensitive R3327-G prostatic adenocarcinoma were used to study the progressive changes that occur in tumor growth rate and androgen sensitivity. Different in vivo transplant generations (21st to 28th) were compared. The tumor doubling and animal survival times resulting from the implantation of the 21st to 22nd generation (21-22G) tumor cells in intact male rats were significantly greater than those resulting from the implantation of 23-28G tumor cells. The most dramatic difference between early (21-23G) and late (26-28G) tumor generations, however, was in androgen sensitivity. The 26-28G tumors displayed androgen sensitivity only when implanted into animals castrated 2 to 7 days previously. Tumors grown in the pretreated castrates grew at a significantly slower rate than those in intact rats and the pretreated castrates had longer survival times than the intact rats. When 26-28G tumors were allowed to grow in intact rats to approximately 1 cu cm and then the rats were castrated, no significant difference in the growth rate between these tumors and tumors grown in intact rats was observed. In contrast, the androgen sensitivity of 21-23G tumors could be demonstrated, regardless of whether treatment was started before or after implantation. The fact that androgen sensitivity was still evident under certain conditions in late-generation R3327-G tumors demonstrates that the basic mechanism involving androgen response was still present, although functioning at a much reduced level.

Adenocarcinoma↗
PubMed1984

Limited choroidal hemorrhage associated with intracapsular cataract extraction.

In a prospective study, limited choroidal hemorrhage (LCH) was found in 16 of 521 eyes (3.07%) subjected to cataract extraction. It developed in ten of 69 highly myopic eyes (14.49%), three of 64 moderately myopic eyes (4.49%), and three of 388 eyes without clinically significant myopia (0.77%). A positive correlation was found between LCH and vitreous loss in myopic eyes. A cause and effect relationship was not established. Of systemic factors investigated, an association was found between LCH and cardiovascular disease (14 of 16 cases). The ophthalmoscopic appearance and clinical findings support the hypothesis that LCH and expulsive choroidal hemorrhage are manifestations of the same disease processes and share common pathophysiologic mechanisms. The cause in any one case is probably multifactorial.

Aged↗
PubMed1984

Quantitation of cell kinetic responses using simultaneous flow cytometric measurements of DNA and nuclear protein.

A rapid procedure was developed for the simultaneous flow cytometric analysis of nuclear protein using fluorescein isothiocyanate, and DNA using propidium iodide in isolated nuclei. The staining procedure did not involve centrifugation and was easily adapted to the staining of human peripheral blood lymphocytes stimulated with phytohemagglutinin, EL4 murine lymphoid tumor cells in suspension culture, and R3327-G rat prostatic adenocarcinoma solid tumor specimens. Histograms of unstimulated and PHA-stimulated HPBL perturbed by actinomycin D, hydroxyurea, 3H-TdR, colcemid, or hydroxyurea + colcemid showed that 1) resting, noncycling G1 (G1Q) cells are distinguished from late G1 (G1AB) cells, 2) early G2 (G2A) cells are distinguished from late G2 (G2B) cells, and 3) mitotic cells are distinguished from G2 cells. Treatment with hydroxyurea resulted in a build-up of cells having high nuclear protein content and 2C DNA content (G1AB), while incubation with 3H-TdR caused an increase in the number of cells with high nuclear protein content and 4C DNA content (G2B). Colcemid-blocked mitotic cells were identified as having low nuclear protein content (lower than G2A nuclei) and 4C DNA content. The nuclear DNA/protein histograms of untreated and colcemid-treated log-phase EL4 cells provided information concerning G1A, G1B, S, G2A, G2B, and M. The method was also used to quantitate the response of androgen-sensitive rat prostatic R3327-G tumors to androgen deprivation following castration. Sample preparation and staining for correlated nuclear DNA/protein measurements takes approximately the same amount of time as for single parameter nuclear DNA measurements.

Adenocarcinoma↗