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Biomedical subjects

A Pollack

Publications and source records attributed to A Pollack.

At least 19 recordsLinked to original sources
PubMed1992

Thymoma. The prognostic significance of flow cytometric DNA analysis.

The clinical course of patients with thymoma varies widely despite its histologically benign appearance. Treatment decisions are based on local invasion and the extent of resection. Because some patients have more aggressive tumors, the prognostic significance of flow cytometric (FCM) analysis of nuclear DNA content was examined. Adequate tissue from paraffin-embedded blocks was available for 25 patients. Using FCM, the percentage of cells in S-phase (%S) and the ploidy, based on the DNA index (DI), were determined. The mean patient age was 52 years, with a female-to-male ratio of 1.3:1 and a median follow-up of 64 months. Seventeen patients underwent total tumor resections, and 12 also received radiation therapy. Eight patients underwent subtotal resections, with five receiving radiation therapy (with or without chemotherapy) and three receiving chemotherapy alone. Based on invasion and intrathoracic dissemination, the tumors were classified into four stages. The mean %S was 5.6. There was no relationship observed between %S and patient outcome. The 5-year disease-free survival rate was 85% for the 16 patients with diploid (DI = 1) tumors and 33% for the 9 patients with aneuploid (DI more than 1) tumors (P less than 0.002). Similar significant differences were observed by stage and extent of surgery. For those who had total resection (n = 17), the disease-free survival rate was 89% when DI equaled 1 and 50% when DI was more than 1 (P = 0.01). Although the numbers studied were small, when stage, histologic findings, and type of surgery were subdivided by DI, a higher incidence of relapse was associated consistently with aneuploidy. The DI appears to be a useful prognostic parameter for identifying patients at high risk of relapse.

Adolescent↗
PubMed1992

Choroidal vascular repair: scanning and transmission electron microscopy.

Repair of the choroidal vasculature following laser photocoagulation in the rat was examined with vascular casts and correlated with observations on thin-sections. The regenerative process began at the periphery of the damaged area, starting from the surviving choriocapillaris and venules, and proceeding towards the center by means of recanalization of damaged vessels and growth of new ones. In small healed lesions the capillary bed was re-formed. It resembled the adjacent undamaged choriocapillaris morphologically but appeared to be less dense than the intact choriocapillaris when examined by scanning microscopy. In large lesions the capillary bed was re-formed at the periphery but not at the center. Also present at the edges of the large lesions were groups of new vessels which, when observed by scanning microscopy, appeared to extend in two directions; towards the subretinal space and towards the choroidal network. Another aspect of the repair process was the simultaneous occurrence of new vessel growth and capillary regression, which was observed both at the level of the choriocapillaris and at the foci of new vessels.

Animals↗
PubMed1992

Autodecremental pacing for the interruption of ventricular tachycardia and atrial flutter.

The efficacy and safety of autodecremental pacing (ADP) to interrupt ventricular tachycardia (VT) and atrial flutter was examined. Once tachycardia was recognized, ADP was initiated using a short train of stimuli with gradual shortening (3%) of the interstimulus interval. ADP was applied to 13 consecutive patients during 75 episodes of VT (mostly following induction by ventricular stimulation). Successful interruption of VT occurred in 88% of the episodes. In 6 episodes (8%), ADP resulted in ventricular fibrillation and in 3 episodes VT was unaffected by ADP. The only significant discriminator between the failure or success of ADP was the rate of VT. ADP was also applied to 17 consecutive patients with an atrial flutter that was resistant to conventional antiarrhythmic agents. Successful conversion of atrial flutter to sinus was seen in only 8 patients (47%). A temporary acceleration to atrial fibrillation appeared in 3 patients (18%), and in 6 patients atrial flutter was unaffected by ADP. ADP was successful in 70% (7/10) of patients with type 1 (< 300 beats/min) atrial flutter. The authors conclude that ADP is beneficial in the interruption of VT and atrial flutter in a selected group of patients, especially with a slower rate of tachyarrhythmia (atrial rate during atrial flutter < 300 beats/min and ventricular tachycardia < 180 beats/min).

Adult↗
PubMed1992

Thymoma: treatment and prognosis.

Thirty-six patients with pathologically confirmed thymoma were treated at M.D. Anderson Cancer Center from 1962 to 1987. The tumors were staged based on invasion and intrathoracic dissemination. Twenty-one patients had total resection, five had subtotal resection, and 10 had biopsy alone. Twenty-two patients had definitive megavoltage radiation therapy with a median dose of 50 Gy. The 5-year, disease-free survival by stage was 74% for Stage I (n = 11), 71% for Stage II (n = 8), 50% for Stage III (n = 10), and 29% for Stage IVA (n = 7) (p less than 0.03). The 5-year, disease-free survival by extent of surgery was 74% for total resection, 60% for subtotal resection and 20% for biopsy only (p = 0.001). There were 15 patients with recurrences: two in Stage I, two in Stage II, five in Stage III, and six in Stage IVA. The median months to relapse, for those who failed treatment, were 46, 36, 2, and 13 for Stages I, II, III, and IVA respectively. Of the patients with recurrences four had a total resection, two subtotal resection, and nine biopsy only. Only one patient had distant metastases as the first site of relapse without intrathoracic relapse. For the eight patients who relapsed following radiation therapy, four were in the radiotherapy field. All four of the in-field failures were in patients who had a partial response. There were insufficient numbers of patients to determine a dose response to radiotherapy. For patients with invasive, incompletely resected disease, a multimodality approach may be necessary for long term, disease-free survival.

Adolescent↗
PubMed1992

Cystoid macular oedema following neodymium:YAG laser capsulotomy a prospective study.

Neodymium:YAG laser capsulotomy was performed in 65 eyes of 65 patients because of vision loss due to posterior capsular opacification or wrinkling following uneventful extracapsular cataract extraction with intraocular lens implantation. Eyes with pre-existing macular pathology were excluded from this study. In all of the eyes the posterior capsule was successfully opened. None developed clinical or angiographic cystoid macular oedema. One eye developed retinal detachment nine months after capsulotomy.

Aged↗
PubMed1992

Cystoid macular oedema following cataract extraction in patients with diabetes.

The course of cystoid macular oedema (CMO) following extracapsular cataract extraction with posterior chamber intraocular lens implantation was prospectively studied in 44 eyes of 44 consecutive diabetic patients without preoperative CMO. In 50% of eyes CMO was observed 6 weeks after surgery and in 25% was still present at 1 year. The preoperative presence of diabetic retinopathy significantly affected the postoperative onset and persistence of CMO. CMO occurred postoperatively in only 32% of eyes without pre-existing diabetic retinopathy and in 81% of eyes with pre-existing diabetic retinopathy (p < 0.05). CMO persisted at 1 year after surgery in only 7% of eyes without pre-existing diabetic retinopathy and in 56% of eyes in which diabetic retinopathy persisted (p < 0.01). Angiographic CMO (that is, detectable only on fluorescein angiography) was more common than clinical CMO (detectable on ophthalmoscopic examination as well) in eyes with no pre-existing diabetic retinopathy, whereas clinical CMO was seen more often than angiographic CMO when diabetic retinopathy was present preoperatively (p < 0.01). The course and final visual outcome of angiographic CMO were more favourable than in clinical CMO. Final visual acuity of at least 6/12 was achieved in 86% of eyes with angiographic CMO and in only 33% of eyes with clinical CMO. On the basis of the above findings we believe that cataract extraction should not be recommended for eyes with pre-existing diabetic retinopathy until the vision has deteriorated to at least 6/30-6/60.

Adult↗
PubMed1992

The course of diabetic retinopathy following cataract surgery in eyes previously treated by laser photocoagulation.

The course of diabetic retinopathy following extracapsular cataract extraction with posterior chamber lens implantation in eyes previously treated by laser photocoagulation for diabetic retinopathy was retrospectively studied in 33 eyes (33 patients). In 20 eyes (61%) there was no change in the retinal status postoperatively. In 13 (39%) there was postoperative progression of diabetic retinopathy compared with the fellow non-operated eye, in which progression occurred in nine eyes (27%). The severity of the preoperative status affected the incidence of progression. Four eyes (12%) developed complications of diabetic retinopathy--that is, rubeosis iridis and vitreous haemorrhage--which regressed after lasering. Cystoid macular oedema developed in 13 eyes (39%) and its incidence varied according to the postoperative course of diabetic retinopathy. The majority of the eyes showed a postoperative improvement in vision.

Adult↗
PubMed1992

Vascular remodeling after laser photocoagulation: concurrent regeneration and atrophy.

Laser photocoagulation is associated with paradoxical results: it causes obliteration of vessels, but leads also to the formation of new ones. In an attempt to better understand this dual vascular response we conducted an ultrastructure study of the choroidal vascular repair following krypton laser injury in rats. Three processes were observed: recanalization, neovascularization, and atrophy of both recanalized and newly formed capillaries. Post-lasering repair of the choroidal vasculature can therefore be described as a remodeling process, characterized by both regeneration and involution. The latter appears to be a secondary process of atrophy, contributing to permanent vascular obliteration. These mechanisms might explain why, in spite of initial vascular regeneration, laser photocoagulation treatment has a beneficial effect on choroidal subretinal neovascularization.

Animals↗
PubMed1992

A semiquantitative scale for histologic grading of articular cartilage repair.

This laboratory has developed a semiquantitative scale for grading the natural healing process of defects drilled into articular cartilage. The scale is composed of four parameters: percent filling of the defect, reconstitution of the osteochondral junction, matrix staining and cell morphology; it has a score range from 0 (best) to 14 (worst). The scale was used to evaluate the healing of defects drilled into rabbit knee articular cartilage at 2, 14, 30, 60 and 120 days after surgery. No statistically significant difference in the graded score was found between the two different defect sizes (2.7 and 1.5 mm). However, the differences in score observed between specimens from different sacrifice times were significant (p less than 0.01). Currently many investigators are manipulating cartilaginous lesions in an attempt to improve healing, and this scale will provide a means for quantitatively comparing results from control and experimental groups.

Animals↗
PubMed1991

Evidence that protein constituents of postsynaptic membrane specializations are locally synthesized: time course of appearance of recently synthesized proteins in synaptic junctions.

Previous studies have led to the hypothesis that some protein constituents of postsynaptic membrane specializations are locally synthesized near postsynaptic sites. The present study focuses on one prediction of this hypothesis, specifically, that if some proteins of the postsynaptic membrane specialization are locally synthesized, then the delay between synthesis and assembly into synaptic junctional membrane could be short. We evaluate the time course of appearance of recently synthesized protein in synaptic junctions by pulse-labeling hippocampal slices maintained in vitro with radiolabeled protein precursors, and then isolating subcellular fractions enriched in synaptic plasma membranes (SPM) and synaptic junctional complexes (SJC). We report that there is no evidence of a delay in the appearance of recently synthesized proteins in SPM and SJC fractions. Labeled proteins could be detected as early as 15 min after the initiation of the pulse-labeling period, and the extent of labeling increased monotonically thereafter. The labeling could not be accounted for by contamination of synaptic membrane fractions with other membranes, because the relative specific activity of the SPM and SJC fractions was the same or higher than that of the less pure fractions from which these synaptic fractions were derived. One-dimensional PAGE-fluorography was used to provide an initial characterization of which proteins were labeled in SJC fractions. We found that the most prominent labeled bands were at apparent molecular weights of approximately 43-44, 55-56, and 60 kd, with more lightly labeled bands at about 38 and 116 kd. In some preparations, there was a labeled doublet at about 36-38 kd. There were also other lightly labeled bands at other molecular weights. These bands were much less heavily labeled than the bands at 43-44, 55-56, and 60 kd, however. There was little labeling in the molecular weight range of the "major psd protein" (the alpha subunit of CAM-kinase), although there was diffuse labeling throughout the 45-52 kd region. These results are consistent with the hypothesis that some of the protein constituents of the postsynaptic junctional complex are synthesized by polyribosomes which are selectively localized beneath synaptic junctions.

Animals↗
PubMed1991

[Central retinal artery occlusion in a young man].

Central retinal artery occlusion (CRAO) is uncommon in those younger than 50. We present a 42-year-old man who complained of sudden loss of vision in the left eye. Fundus examination showed typical findings of CRAO. Extensive medical work up showed no evidence of diabetes or of cardiovascular, hematologic or collagen disease. However, a malignant tumor of the right testis was found, with metastases in the lung, retroperitoneal lymph nodes and brain. The right testis was resected and chemotherapy and brain irradiation resulted in remission during a follow-up of 2.5 years. The differential diagnosis of CRAO in younger patients is difficult. We believe that metastases from the primary tumor were the cause of CRAO in our patient. The possibility of malignancy with metastatic spread causing CRAO should be considered, particularly in relatively young patients with no other evidence of systemic disease.

Adult↗
PubMed1979

Differences in flow cytometry and 3H-thymidine analyses of perturbed human lymphocytes.

A calf thymocyte crude aqueous extract was tested for DNA synthesis inhibitory activity using phytohemagglutinin-stimulated human peripheral blood lymphocytes. Inhibition of DNA synthesis was assayed using tritiated thymidine and flow cytometry. Although the calf thymocyte crude extract inhibited tritiated thymidine incorporation by over 50%, only very slight changes in the flow cytometric analysis were observed. When dibutyryl-cyclic adenosine monophosphate was used as an inhibitor, a correlation in terms of the inhibition of tritiated thymidine to the inhibition by flow cytometry was observed.

Animals↗
PubMed1977

(-)-Hydroxycitrate and conditioned aversions.

The capacity of various salts of (-)-hydroxycitrate to produce conditioned rejection of a 0.25% saccharin solution was evaluated. The ethylenediamine salt of (-)-hydroxycitrate produced strong conditioned rejection of saccharin under both deprivation and nondeprivation conditions, but this effect was less than produced by equimolar doses of lithium chloride. The sodium salt of hydroxycitrate produced no conditioned rejection of saccharin in water deprived rats but did so in nondeprived animals. In these experiments, food intake was reduced by (-)-hydroxycitrate only during the first hour following administration of the drug. The magnitude of appetite rejection did not correspond to the degree of conditioned rejection, lending support to the conclusion that the food intake reduction was not merely a consequence of aversive effects of the drug.

Animals↗