Biomedical subjects

S Lacy

Publications and source records attributed to S Lacy.

7 recordsLinked to original sources

PubMed1999

A new pathway for mitogen-dependent cdk2 regulation uncovered in p27(Kip1)-deficient cells.

BACKGROUND: The ability of cyclin-dependent kinases (CDKs) to promote cell proliferation is opposed by cyclin-dependent kinase inhibitors (CKIs), proteins that bind tightly to cyclin-CDK complexes and block the phosphorylation of exogenous substrates. Mice with targeted CKI gene deletions have only subtle proliferative abnormalities, however, and cells prepared from these mice seem remarkably normal when grown in vitro. One explanation may be the operation of compensatory pathways that control CDK activity and cell proliferation when normal pathways are inactivated. We have used mice lacking the CKIs p21(Cip1) and p27(Kip1) to investigate this issue, specifically with respect to CDK regulation by mitogens. RESULTS: We show that p27 is the major inhibitor of Cdk2 activity in mitogen-starved wild-type murine embryonic fibroblasts (MEFs). Nevertheless, inactivation of the cyclin E-Cdk2 complex in response to mitogen starvation occurs normally in MEFs that have a homozygous deletion of the p27 gene. Moreover, CDK regulation by mitogens is also not affected by the absence of both p27 and p21. A titratable Cdk2 inhibitor compensates for the absence of both CKIs, and we identify this inhibitor as p130, a protein related to the retinoblastoma gene product Rb. Thus, cyclin E-Cdk2 kinase activity cannot be inhibited by mitogen starvation of MEFs that lack both p27 and p130. In addition, cell types that naturally express low amounts of p130, such as T lymphocytes, are completely dependent on p27 for regulation of the cyclin E-Cdk2 complex by mitogens. CONCLUSIONS: Inhibition of Cdk2 activity in mitogen-starved fibroblasts is usually performed by the CKI p27, and to a minor extent by p21. Remarkably p130, a protein in the Rb family that is not related to either p21 or p27, will directly substitute for the CKIs and restore normal CDK regulation by mitogens in cells lacking both p27 and p21. This compensatory pathway may be important in settings in which CKIs are not expressed at standard levels, as is the case in many human tumors.

Animals↗

PubMed1999

Divergence between stone composition and urine supersaturation: clinical and laboratory implications.

PURPOSE: In general high urine supersaturation with respect to calcium oxalate, calcium phosphate or uric acid is associated with that phase in stones. We explore the exceptions when supersaturation is high and a corresponding solid phase is absent (type 1), and when the solid phase is present but supersaturation is absent or low (type 2). MATERIALS AND METHODS: Urine supersaturation values for calcium oxalate, calcium phosphate and uric acid, and other accepted stone risk factors were measured in 538 patients at a research clinic and 178 at stone prevention sites in a network served by a single laboratory. RESULTS: Of the patients 14% lacked high supersaturation for the main stone constituent (type 2 structural divergence) because of high urine volume and low calcium excretion, perhaps from changes in diet and fluid intake prompted by stones. Higher calcium excretion and low urine volume caused type 1 divergences, which posed no clinical concern. CONCLUSIONS: Type 1 divergence appears to represent a condition of low urine volume which raises supersaturation in general. Almost all of these patients are calcium oxalate stone formers with the expected high supersaturation with calcium oxalate as well as high uric acid and calcium phosphate supersaturations without either phase in stones. Type 2 divergence appears to represent an increase in urine volume and decrease in urine calcium excretion between stone formation and urine testing.

Calcium Oxalate↗

PubMed1998

Medical reduction of stone risk in a network of treatment centers compared to a research clinic.

PURPOSE: We determined whether a network of 7 comprehensive kidney stone treatment centers supported by specialized stone management software and laboratory resources could achieve reductions in urine supersaturation comparable to those in a single research clinic devoted to metabolic stone prevention. MATERIALS AND METHODS: Supersaturation values for calcium oxalate, calcium phosphate and uric acid in 24-hour urine samples were calculated from a set of kidney stone risk factor measurements made at a central laboratory site for the network and research laboratory for the clinic. Individual results and group outcomes were presented to each center in time sequential table graphics. The decrease in supersaturation with treatment was compared in the network and clinic using analysis of variance. RESULTS: Supersaturation was effectively reduced in the network and clinic, and the reduction was proportional to the initial supersaturation value and increase in urine volume. The clinic achieved a greater supersaturation reduction, higher fraction of patient followup and greater increase in urine volume but the treatment effects in the network were, nevertheless, substantial and significant. CONCLUSIONS: Given proper software and laboratory support, a network of treatment centers can rival but not quite match results in a dedicated metabolic stone research and prevention clinic. Therefore, large scale stone prevention in a network system appears feasible and effective.

Adult↗

PubMed1997

Identification of a p130 domain mediating interactions with cyclin A/cdk 2 and cyclin E/cdk 2 complexes.

P130 shares structural and functional homology with pRb and p107. One property common to p107 and p130, but not to pRb, is the ability to stably interact with cyclin A/cdk2 and cyclin E/cdk2 complexes in vitro and in vivo. Using GST-p130 fusion proteins representing various regions of p130, baculovirus-produced cyclin A/cdk2 and cyclin E/cdk2 complexes were found to interact with residues within a part of p130 known as the spacer region. Cyclin E was able to bind the p130 spacer region in the presence or absence of cdk2 whereas cyclin A binding was dependent upon the presence of cdk2. The smallest p130 fusion protein sufficient to interact with cyclin A/cdk2 or cyclin E/cdk2 complexes contained p130 amino acids 652-698 and deletion of p130 amino acids 680-682 abolished binding to both of the cyclin/cdk2 complexes. When overexpressed in C33A cells, a p130 mutant containing a deletion of amino acids 620-697 was unable to form complexes with either cyclin A or cyclin E. This p130 mutant was at least as active as wild type p130 in suppressing the growth of G418 resistant colonies when overexpressed in C33A or SAOS-2 cells.

CDC2-CDC28 Kinases↗

PubMed1993

The adenovirus E1A-associated 130-kD protein is encoded by a member of the retinoblastoma gene family and physically interacts with cyclins A and E.

The adenovirus E1A proteins form complexes with a group of cellular proteins, including a protein of 130 kD. E1A-associated p130 was purified through coimmunoprecipitation with E1A, and sequence data from four tryptic peptides was obtained. Oligonucleotides derived from the peptide sequences were used to clone a 4.85-kb cDNA. The cDNA contained an 1139-amino-acid open reading frame with homology to the retinoblastoma protein and E1A-associated p107 but was more closely related to p107. In vitro-translated p130 bound to E1A, and anti-p130 antibodies detected p130 in immunoblots of E1A immunoprecipitates. p130 was also detected in immunoprecipitates of cyclins A and E and was an efficient substrate in vitro for kinase activities associated with these cyclins. The p130 gene mapped to chromosome 16q12.2-13, a region that undergoes allelic loss in several types of tumors, including hepatocellular, prostate, and breast carcinomas.

Adenovirus E1A Proteins↗

PubMed1992

Laparoscopic para-aortic lymph node sampling: development of a technique.

Clinical staging is woefully inadequate in predicting lymph node metastasis and dictating prudent radiation ports in women undergoing therapy for cervical malignancies. Surgical staging with evaluation of the precaval lymph nodes (via a transperitoneal or extraperitoneal approach) has associated rates of complication that are felt by many clinicians to be excessive. A laparoscopic approach could avoid many of these complications while still obtaining valuable information regarding spread of disease. After experimentation with different forms of laparoscopic approaches in the swine model, we have found an easy and efficient way to visualize and sample the infrarenal precaval lymph nodes. The laparoscope is placed suprapubically, and accessory operating trocars are placed suprapubically and periumbilically. Laparoscopically placed sutures are placed on the incised posterior peritoneum. The sutures exit through the periumbilical trocars. When drawn taut, the sutures pull the peritoneum in a cephalad and ventral fashion so as to act as a tent, retracting the intraperitoneal contents and exposing the precaval area. Using this technique in the swine, we were able to remove 88% of all right-side common iliac and paraaortic nodes laparoscopically without injuring surrounding structures. Evaluation of this technique in humans should be considered.

Animals↗

PubMed1990

Pulmonary lesions induced by 3-methylindole and bovine respiratory syncytial virus in calves.

Our objectives were to describe the ultrastructural morphogenesis of pulmonary lesions induced by 3-methylindole in 30- to 45-day-old Holstein calves and to determine whether toxic exposure to 3-methylindole exacerbates pulmonary lesions induced by bovine respiratory syncytial virus. Administration of 3-methylindole (0.25 g/kg) to calves resulted in interstitial edema and ultrastructural swelling of type-I alveolar epithelial cells and nonciliated bronchiolar epithelial cells as early as 4 to 6 hours after intraruminal administration. More severe alveolar edema containing protein was associated with swelling of capillary endothelial cells at 2 days after administration. Proliferation of type-II alveolar epithelial cells was first observed at 2 days after 3-methylindole administration, and marked hyperplasia of type-II epithelial cells and nonciliated bronchiolar epithelial cells was evident by 4 days after administration. Pulmonary cytochrome P-450 monooxygenase concentrations decreased significantly (P less than 0.001) by 12 hours after administration and did not increase significantly again by 8 days after administration. Calves were inoculated with bovine respiratory syncytial virus 3 days after administration of 3-methylindole, and pulmonary lesions were assessed 5 days after viral inoculation. Viral replication was demonstrated by fluorescence microscopy for viral antigen or by transmission electron microscopy in ciliated and nonciliated airway epithelial cells. Viral antigen was identified infrequently in alveolar macrophages and in type-II alveolar epithelial cells. 3-Methylindole exposure in calves did not result in more widespread distribution of viral antigen in alveolar tissue of respiratory syncytial virus-inoculated calves or in significant enhancement of viral pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗