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Biomedical subjects

C A Schmidt

Publications and source records attributed to C A Schmidt.

101 records · Page 6Linked to original sources
PubMed1985

Cross-linking of Novikoff ascites hepatoma cytokeratin filaments.

We have investigated the structure of solubilized cytokeratins from Novikoff ascites hepatoma using the cleavable cross-linker 3,3'-dithiobis(sulfosuccinimidyl propionate) in the presence of 6 M urea to effect partial complex melting. By two-dimensional gel electrophoresis, in which the protein cross-links were broken in the second dimension, we have identified two major complexes as a p39-p56 dimer and a (p39-p56)2 tetramer, p39 and p56 being two of the major cytokeratins in Novikoff ascites hepatoma. Experiments investigating possible relationships between the dimer and tetramer employed immunoblots and two monoclonal antibodies which recognized either p56 or p39 cytokeratins. When very low protein concentrations were cross-linked, the dimer was the predominant product. As protein concentration increased, we noted a decrease in dimers and a corresponding increase in tetramers, suggesting that the dimer may be a precursor to the tetramer. In support of the cross-linking experiments, two-dimensional gel electrophoresis using 4 M urea in the first dimension indicated a predominant association of p56 and p39 in the Novikoff ascites hepatoma cytokeratin complexes.

Animals↗
PubMed1984

Thoracic aortic injury. A ten-year experience.

Between 1974 and 1983, 41 patients arrived alive at Loma Linda (Calif) University Medical Center after sustaining a traumatic disruption of the thoracic aorta. Four patients died during the resuscitation attempts and the 37 patients who survived underwent thoracotomy for attempted definitive repair. There were six hospital deaths (16.22%) among those who underwent definitive repair; associated injuries (mostly orthopedic and neurologic) were contributing factors. Four patients were discharged with spinal cord injuries, two were paraplegic on arrival at the hospital, and two became paraplegic postoperatively (surgical spinal cord injury, 5.41%). Most injuries were distal to the left subclavian artery (97.56%). Cardiopulmonary (left heart) bypass was gradually abandoned in favor of more simple techniques, including ventriculoaortic and aorto-aortic heparinized shunts or a "clamp and sew" method. Experience has demonstrated that most traumatic aortic disruptions can be repaired safely by direct suture technique (without graft interposition) if accomplished during the acute episode.

Adolescent↗
PubMed1984

Association of cytokeratin p39 with DNA in intact Novikoff hepatoma cells.

The relationship between the rat tumor-associated cytokeratin p39 (Mr 39,000) and cellular DNA has been studied in intact cells. Using a DNA-protein crosslinking technique, incubation with cis-dichlorodiammineplatinum, we present evidence for the association of p39 with DNA in intact Novikoff ascites hepatoma cells. The cells were treated with cis-dichlorodiammineplatinum and solubilized in NaDodSO4-containing buffer, and the DNA was pelleted by high-speed centrifugation. By immunotransfer analysis, the cytokeratin was found in the DNA pellet of the crosslinked samples while absent from the controls. This result was further substantiated by CsCl density-gradient centrifugation. Collectively, these results suggest a cytokeratin-DNA association at the filament binding sites on or near the nuclear lamina.

Animals↗
PubMed1984

Characterization of monoclonal antibodies to novikoff hepatoma cytokeratin antigen p39.

Three stable monoclonal antibody-producing mouse hybridoma lines have been developed which produce high-titer, immunoglobulin M antibodies specific for the Novikoff ascites hepatoma (NAH) Mr 39,000 cytokeratin antigen (p39). Immunotransfer assays of cytoskeletal protein-enriched fractions indicated p39 to be present in a range of rat tissues, including colon, breast, lung, and uterus. Two-dimensional gel immunoblots confirmed that immunoreactivity in the latter tissues was for polypeptides with similar isoelectric points to those of NAH p39; however, reactivity in the colon contained a wide range of additional isomeric forms. Immunohistochemical localization studies with these antibodies revealed enrichment of p39 in the simple epithelia or ductular structures of organs containing this antigen. In all sections examined, glandular epithelia were observed to be only weakly immunoreactive. Additional immunoblot and immunocytochemical analyses with the monoclonal antibodies and polyspecific antisera to NAH cytokeratin suggest the human Mr 40,000 cytokeratin to be similar to but not identical to NAH p39.

Animals↗
PubMed1984

Nuclear matrix antigens in azo dye-induced primary rat hepatomas.

Polyvalent antisera, monoclonal antibodies, and immunotransfer methodology have been used to identify and characterize a group of chromosomal protein antigens which appear during azo dye hepatocarcinogenesis. Experiments were designed to probe for the location and placement of antigens in chromatin according to solubility and possible DNA-binding properties. The majority of nuclear antigens were associated with high-speed DNA-containing pellets after ultracentrifugation of chromatin solubilized with denaturing buffers containing 6 M guanidine-HCl:2% sodium dodecyl sulfate, or 2 M NaCl:5 M urea. The addition of 2-mercaptoethanol or dithiothreitol to guanidine-HCl or sodium dodecyl sulfate solutions resulted in solubilization of nearly all antigens from the DNA pellets, suggesting the presence of complexes (protein:protein and/or DNA:protein) cross-linked with sulfhydryl linkages. Preparation of nuclear matrix from the primary hepatomas under several kinds of conditions indicated these antigens to be components of the residual nuclear matrix, envelope, and/or associated structures. Two-dimensional gel analysis showed most antigens to exist in a range of isoelectric forms, suggesting posttranslational modifications. Studies with monoclonal antibodies prepared to these proteins revealed extensive antigenic homology among the members comprising these fractions. Our results document antigenic differences in the nuclear matrix proteins of primary tumors and their normal tissue counterparts.

Amino Acids↗
PubMed1983

Arteriovenous fistula in arterial reconstruction of the ischemic limb.

The high flow associated with an arteriovenous fistula has been shown to help maintain patency in small arterial anastomoses. In 37 male patients we created common ostium arteriovenous fistula at the distal tibial or peroneal anastomosis as a part of their arterial reconstruction for threatened limb loss. Limb salvage was achieved in 28. Successful amputations at a lower level than would have been anticipated were performed in three. There was early graft failure in four patients resulting in below-the-knee amputations. This operative approach may be helpful in patients who have had previous revascularization procedures that have failed, who resist the idea of amputation, and who fulfill the angiographic criteria of extremely poor runoff with an absent or deficient pedal arch.

Adult↗
PubMed1980

Septal wall motion. Its significance on outcome of left ventricular scar resection.

To assess the importance of septal wall motion on patient outcome after resection of large akinetic and dyskinetic segments of left ventricle, the records of 70 patients undergoing left ventricular scar excision alone or in combination with myocardial revascularization procedures between January 1970 and January 1977 were reviewed. Patients requiring simultaneous prosthetic valve replacement were excluded. Preoperative left anterior oblique ventriculograms categorized this series of patients into two distinct groups, group A (36 patients) having normal septal wall motion and group B (34 patients) having akinetic or dyskinetic septal walls. Indications for operation and preoperative ejection fractions were similar in both groups. Analysis of these patients subjected to surgery with and without preoperative evidence of septal wall motion demonstrated no significant difference in either functional clinical capacity or in mortality. Mortality for both groups was 11%. Absence of ventricular septal wall motion has no significant effect on outcome of left ventricular scar resection and should not be used as a contraindication to surgery.

Angina Pectoris↗
PubMed1980

Comparative inactivation of viruses by chlorine.

The kinetics of inactivation of six enteric viruses plus simian virus 40 and Kilham rat virus by free available chlorine was studied under carefully controlled laboratory conditions. It was found that the different virus types demonstrated a wide range of susceptibility to chlorine disinfection. The rate of inactivation was greater at pH 6 than at pH 10; however, the relative susceptibilities of the different viruses were affected differently by a change in pH, suggesting that the pH influenced both the species of chlorine present and the susceptibility of the different viruses to chlorine. The presence of potassium chloride also affected the susceptibility of viruses to chlorine.

Antiviral Agents↗
PubMed1980

Patterns of transcription of human cytomegalovirus in permissively infected cells.

The rate of accumulation of cytomegalovirus transcripts in permissively infected human embryonic lung (HEL) cells was analyzed at various times after infection by hybridization of infected cell RNA to undigested or restriction endonuclease-digested cytomegalovirus DNA fixed to nitrocellulose filters. Differences in patterns of transcript accumulation were determined by measuring the abundance levels of RNA which hybridized to different HindIII-, XbaI-, or EcoRI-generated fragments of cytomegalovirus DNA. The results showed that a small but significant amount of cytomegalovirus RNA was detectable within the first 3 h after infection and that the rate of accumulation of these transcripts was static during the first 24 h, but increased thereafter. In general, the viral transcripts accumulating in infected cells could be divided into three classes. Immediate-early RNA (synthesized in the absence of protein synthesis in infected cells) hybridizes predominantly to a very restricted part of the genome and can be identified during the first 2 to 4 h postinfection. Early RNA (synthesized up to about 24 h after infection) originates from most regions of the genome but is characterized by the presence of transcripts which hybridize in great abundance to certain fragments. Late RNA (synthesized after 24 h, i.e., after the onset of viral DNA synthesis) hybridizes in approximately equal abundance to most regions of the viral genome. These results showed that a block in the transition from immediate-early to early RNA did not account for the extended period of time that elapses between the time of infection and the initiation of viral DNA synthesis. Interestingly, despite rapid adsorption and penetration and a static level of accumulation of transcripts in the cultures during the first 24 h, the number of cells that synthesized detectable amounts of viral antigens increased steadily during this time.

Antigens, Viral↗