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Biomedical subjects

J Snyder

Publications and source records attributed to J Snyder.

At least 91 records · Page 5Linked to original sources
PubMed1978

Carcinoembryonic antigen (CEA) plasma levels in Michigan and Wisconsin dairy farmers.

Carcionogenic embryonic antigen (CEA) titers were determined for 611 Michigan farmers exposed to PBB and a control nonexposed population of 139 Wisconsin farmers. The overall prevalence of elevated CEA titers was slightly higher in the Michigan study group, but the difference was not statistically significant. Smoking and/or significant past or present conditions (inflammatory bowel disease, ulcers, polyps, liver disease, chronic lung disease, or malignancies) were found to result in higher prevalence of elevated CEA titers, in both the Michigan study group and the Wisconsin control group, thus confirming previous reports. In addition, serum PBB concentrations appeared to be positively correlated with CEA titers. The possibility that the effect of PBB concentrations appeared to be positively correlated with CEA titers. The possibility that the effect of PBB may be additive to that of other factors which are known to result in an increased prevalence of elevated CEA titers is discussed.

Adolescent↗
PubMed1977

Unit gravity sedimentation separation of cells comprising the caput epididymidis of the rat.

Cells from the rat caput epididymidis were separated by unit gravity sedimentation. Purest 12-ml fractions contained 88-95% basal cells or 64-76% principal cells. Ultrastructure of separated cells was similar to that of cells in intact tissue. Viability of separated cells was excellent as determined by dye exclusion tests and cellular ATP content. By combining fractions pools containing 4.0 +/- 0.9 X 10(6) cells (86 +/- 8% basal cells) and 1.4 +/- 0.4 X 10(6) cells (56 +/- 7% principal cells) were obtained. Thus, studies on the function of basal and principal cells from the rat caput epididymidis should be possible.

Animals↗
PubMed1977

Functional heterogeneity in somatotrophs isolated from the rat anterior pituitary.

Somatotrophs in suspensions of anterior pituitary cells from adult male rats can be separated into 2 fractions by density gradient centrifugation. In addition to their different densities, somatotrophs in these 2 fractions can be distinguished morphologically by their staining characteristics and ultrastructure. Somatotrophs of lesser density (type I; approximately 1.068 g/cm3) have fewer secretory granules and a more extensive Golgi apparatus than the somatotrophs of greater density (type II; approximately 1.073 g/cm3). Responsiveness of type I and type II cells to secretory agents (i.e., dibutyryl cyclic adenosine monophosphate, somatostatin, thyroxine, and hydrocortisone) was evaluated by GH radioimmunoassay. Type I cells were consistently more responsive (% GH release) than type II cells. During 7 days in culture, type I cells produced more (approximately 200%) GH than they initially contained, whereas type II cells did not show evidence of increased GH production. Hydrocortisone significantly stimulated GH production in type I, but not type II cells. These results support the hypothesis that at least 2 functionally distinct populations of somatotrophs are present in the anterior pituitary gland of the adult male rat.

Animals↗
PubMed1976

Characterization of mammotrophs separated from the human pituitary gland.

Human pituitary tissues from 27 patients and 7 persons post mortem were dissociated into single cell suspensions. On the average, 23% of the cells were mammotrophs. The concentration of prolactin in these suspensions averaged 3.8 ng/1,000 cells. After cell separation by velocity sedimentation at unit gravity, mammotrophs and other cell types were enriched twofold to threefold. The separated mammotrophs retained structural integrity at light and electron microscopic levels. In eight separation experiments, cells recovered from different gradient regions were assayed for intracellular prolactin levels. In cells from "normal" subjects, 8.5% of the prolactin recovered from the gradient was associated with large mammotrophs, whereas in patients with breast cancer, 28% of the hormone was associated with large mammotrophs. The number of mammotrophs recovered from this gradient region (beyond fraction 6) was doubled in breast cancer (2 expts). These mammotrophs showed areas of hypertrophied Golgi and endoplasmic reticulum. Culture of the separated cells from 1 patients with diabetes and 2 patients with breast cancer for 21 days showed that mammotrophs in the upper gradient fractions (diabetic) secreted seven times more hormone than those in the lower regions, whereas those mammotrophs from patients with breast cancer that fell to the lower gradient regions secreted 15 times more prolactin than did those in the upper regions. These data suggest that pituitaries of patients with breast cancer contain a small pool (10-20%) of hypertrophied mammotrophs that have the potential for significant secretory activity in vitro.

Adult↗
PubMed1976

Maintenance of separated rat pituitary mammotrophs in cell culture.

Dispersed female rat anterior pituitary cells were cultured in Medium 199 containing 20% fetal calf serum for 30 days. Prolactin levels in the culture medium remained relatively constant during this time, ranging from 30-40 ng/10,000 cells seeded/day. The total quantity of prolactin released into the medium was 10-15 times that originally contained in the cells. Morphological integrity of the mammotrophs was maintained. Using velocity sedimentation at unit gravity, cells from untreated, overiectomized or estrogen-primed animals were separted into several fractions, and subsequently cultured for 14 days. Not all mammotrophs secreted the same quantity of hormone during this time. The data suggest that the pituitary of the female rat is composed of a heterogeneous population of mammotrophs, and that their capacity to secrete prolactin in vitro may, in part, be reflected by the previous physiological status of the animal.

Animals↗
PubMed1975

Biological markers in breast carcinoma. I. Incidence of abnormalities of CEA, HCG, three polyamines, and three minor nucleosides.

Patients with breast carcinoma were screened for abnormal concentrations of CEA, HCG, putrescine, spermidine, spermine, pseudouridine, N2, N2-dimethylguanosine, and 1-methylinosine. Abnormal polyamine levels occurred in less than 15% of the patients. Among the nucleosides, N2, N2-dimethylguanosine was the most frequently abnormal, occurring in 57% of the patients with metastatic disease. CEA levels were abnormal in 30% of postoperative N+ patients and 74% of patients with metastatic disease, while HCG elevations were found in 45% and 50%, respectively. All the patients with one or more marker abnormalities could be detected by measuring only CEA, N2, N2-dimethylguanosine, and HCG. Among these three tests, a singular marker abnormality occurred in 35.8% of the patients, and all three tests were abnormal in 21.8% of the patients. The performance of these three tests in each patient revealed one or more abnormalities 97% of the patients with metastatic disease, and 67% of the postoperative N+ patients.

Breast Neoplasms↗
PubMed1975

A review of total brain ischaemia models in dogs and original experiments on clamping the aorta.

Dog models of total brain ischaemia for the study of pathophysiological mechanisms and post-resuscitative therapy used since 1970 are reviewed. Attempts to produce isolated total cerebral ischaemia in dogs either failed to stop cerebral circulation completely because of the abundance of collateral vessels or involved complex operations with blood loss. Complete airway obstruction resulted in various periods of asphyxia preceding asystole. Total circulatory arrest by ventricular fibrillation for 12 min or longer, resulting in gross neurological deficit, required cardiopulmonary resuscitation of variable duration and often required thoracotomy to restart spontaneous circulation. An acceptable model for short-term studies was obtained by clamping the ascending aorta for 15 min. This resulted in control of perfusion pressure with precise timing of onset and termination of cerebral ischaemia, and an isoelectric electroencephalogram within a mean time of 37 (26-44) s; it retained its ability to restore spontaneous circulation promptly with special supportive therapy, and a severe neurological deficit was evident for 20 h after ischaemia. Reliable total brain ischaemia suitable for long-term survival studies could not be developed in the dog without major surgical procedures, as it has been in the rhesus monkey. Sixteen minutes of high-pressure neck occlusion with a tourniquet and special intensive care resulted in major neurological deficit with survival for at least 7 days, and proved suitable for simultaneous study of neurological, physiological and histological changes.

Animals↗
PubMed1975

Total brain ischaemia in dogs: cerebral physiological and metabolic changes after 15 minutes of circulatory arrest.

Cross-clamping of the ascending aorta in dogs for 15 min produced severe neurological deficit, observed for up to 20 h. Immediately after restoration of the circulation, the intracranial pressure in the cisterna magna increased transiently to a mean peak of 22.8 Torr (SD +/- 1.7) because of a compensatory increase in systemic arterial pressure, without a fall in cerebral perfusion pressure. The intracranial pressure returned to control values 15-30 min after ischaemia and showed no secondary rise during the 8 h of observation. The electroencephalogram became isoelectric 34 +/- 6.5 s (mean +/-SD) after circulatory occlusion, and was abnormal when it reappeared 5 h 36 min (SD +/- 2 h 4 min) after the circulation was restored. The electrical impedance of the brain increased immediately after ischaemia and returned rapidly towards pre-ischaemic values during re-perfusion. The cerebral water had not increased measurably 4 h after ischaemia. After ischaemia, the lactate concentration in the cerebrospinal fluid increased to 4.7 mequiv./1(SEM +/-0.1) and the pH decreased to 7.17 (SEM +/-0.02); both returned to control values after 3.5 h. The cerebral glucose uptake was decreased 35 min after ischaemia, cerebral oxygen uptake remained unchanged but cerebral blood flow decreased (P less than 0.05 at 90 min). Immediately after cardiac arrest, recovery was impaired more by the presence of focal abnormal brain perfusion than by intracranial hypertension.

Animals↗
PubMed1974

A functional mitotic spindle prepared from mammalian cells in culture.

MITOTIC CELLS LYSED INTO SOLUTIONS OF POLYMERIZABLE MICROTUBULE PROTEIN CONTAIN A SPINDLE WHICH IS SIMILAR TO THE LIVING SPINDLE IN TWO RESPECTS: it will lose and gain birefringence when cooled and warmed, and it will move anaphase chromosomes to the opposite ends of the cell. Early anaphase cells lysed into buffers containing high molecular weight polyethylene glycol and nucleotide triphosphates will continue chromosome motion and spindle elongation in the absence of exogenous spindle subunits. These results suggest that while spindle growth requires microtubule polymerization, anaphase motions do not.

Animals↗