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Biomedical subjects

L Howard

Publications and source records attributed to L Howard.

At least 19 recordsLinked to original sources
PubMed1997

Transmembrane/cytoplasmic domain-mediated membrane type 1-matrix metalloprotease docking to invadopodia is required for cell invasion.

The invasion of human malignant melanoma cells into the extracellular matrix (ECM) involves the accumulation of proteases at sites of ECM degradation where activation of matrix metalloproteases (MMP) occurs. Here, we show that when membrane type 1 MMP (MT-MMP) was overexpressed in RPMI7951 human melanoma cells, the cells made contact with the ECM, activated soluble and ECM-bound MMP-2, and degraded and invaded the ECM. Further experiments demonstrated the importance of localization of the MT-MMP to invadopodia. Overexpression of MT-MMP without invadopodial localization caused activation of soluble MMP-2, but did not facilitate ECM degradation or cell invasiveness. Up-regulation of endogenous MT-MMP with concanavalin A caused activation of MMP-2. However, concanavalin A treatment prevented invadopodial localization of MT-MMP and ECM degradation. Neither a truncated MT-MMP mutant lacking transmembrane (TM) and cytoplasmic domains (DeltaTMMT-MMP), nor a chimeric MT-MMP containing the interleukin 2 receptor alpha chain (IL-2R) TM and cytoplasmic domains (DeltaTMMT-MMP/TMIL-2R) were localized to invadopodia or exhibited ECM degradation. Furthermore, a chimera of the TM/cytoplasmic domain of MT-MMP (TMMT-MMP) with tissue inhibitor of MMP 1 (TIMP-1/TMMT-MMP) directed the TIMP-1 molecule to invadopodia. Thus, the MT-MMP TM/cytoplasmic domain mediates the spatial organization of MT-MMP into invadopodia and subsequent degradation of the ECM.

Amino Acid Sequence↗
PubMed1997

Identification of the 170-kDa melanoma membrane-bound gelatinase (seprase) as a serine integral membrane protease.

The 170-kDa membrane-bound gelatinase, seprase, is a cell surface protease, the expression of which correlates with the invasive phenotype of human melanoma and carcinoma cells. We have isolated seprase from cell membranes and shed vesicles of LOX human melanoma cells. The active enzyme is a dimer of N-glycosylated 97-kDa subunits. Sequence analysis of three internal proteolytic fragments of the 97-kDa polypeptide revealed up to 87.5% identity to the 95-kDa fibroblast activation protein alpha (FAPalpha), the function of which is unknown. Thus, we used reverse transcription-polymerase chain reaction to generate a 2.4-kilobase cDNA from LOX mRNA with FAPalpha primers. COS-7 cells transfected with this cDNA expressed a 170-kDa gelatinase that is recognized by monoclonal antibodies directed against seprase. Sequence analysis also showed similarities to the 110-kDa subunit of dipeptidyl peptidase IV (DPPIV). Like DPPIV, the gelatinase activity of seprase was completely blocked by serine-protease inhibitors, including diisopropyl fluorophosphate. Seprase could be affinity-labeled by [3H]diisopropyl fluorophosphate, but the proteolytically inactive 97-kDa subunit could not, confirming the existence of a serine protease active site on the dimeric form. Proteolytic activity is lost upon dissociation into its 97-kDa subunit following treatment with acid, heat, or cysteine and histidine-modifying agents. We conclude that seprase, FAPalpha, and DPPIV are related serine integral membrane proteases and that seprase is similar to DPPIV, the proteolytic activities of which are dependent upon subunit association.

Amino Acid Sequence↗
PubMed1997

Surfaces modified with PEO by the Williamson reaction and their affinity for proteins.

Poly(ethylene oxide) (PEO) was immobilized by the Williamson ether synthesis onto halogenated surfaces such as poly(vinylidene chloride), surface-brominated polypropylene, and surface-brominated poly(ethylene terephthalate). PEO (Mw 20,000) was converted to its sodium salt and reacted for various times with the halogen-containing surfaces at 95 degrees C in the melt, or as a solution in 2-methoxyethyl ether. X-ray photon spectroscopy and water contact-angle measurements confirmed the surface-immobilization of PEO. The adsorption from phosphate buffer of human serum albumin, immunoglobulin G (IgG) and fibrinogen, and murine IgG was reduced after modification of the surfaces. In addition, IgG adsorption from pooled human sera was diminished. The difference in protein adsorption between test samples and controls exhibited a strong dependence on input protein concentration.

Adsorption↗
PubMed1997

Impact factors of psychiatric journals.

BACKGROUND: We examined citation data for the British Journal of Psychiatry (BJP) and four other general psychiatry journals to assess their impact on the scientific community. METHOD: Data on three measures of citations (total number of citations, impact factor and ranking by impact factor) were obtained from Journal Citation Reports for 1985-1994. Rank correlations from year to year were calculated. RESULTS: The BJP currently ranks sixth of all psychiatry journals when journals are ranked by impact factor. The journal's impact factor fell between 1985 and 1990 and this was followed by a rise in impact factor after 1991. The BJP did not rank in the top 10 psychiatry journals between 1991 and 1993. Archives of General Psychiatry is cited more frequently than any other psychiatry journal, with the American Journal of Psychiatry usually ranking second. Psychopharmacology journals are replacing more general journals in the top rankings. Rankings of most journals have become less stable in recent years. CONCLUSIONS: The BJP would have to change the nature and number of papers published to improve its impact factor. There are a number of limitations to citation data and such data are only one of several factors useful in evaluating the importance of a journal's contribution to scientific and clinical communities.

Bibliometrics↗
PubMed1997

Phosphorylation regulates the assembly of NuMA in a mammalian mitotic extract.

NuMA is a 236 kDa nuclear protein that is required for the organization of the mitotic spindle. To determine how NuMA redistributes in the cell during mitosis, we have examined the behavior of NuMA in a mammalian mitotic extract under conditions conducive to the reassembly of interphase nuclei. NuMA is a soluble protein in mitotic extracts prepared from synchronized cultured cells, but forms insoluble structures when the extract becomes non-mitotic (as judged by the inactivation of cdc2/cyclin B kinase and the disappearance of mpm-2-reactive antigens). These NuMA-containing structures are irregularly shaped particles of 1-2 microm in diameter and their assembly is specific because other nuclear components such as the lamins remain soluble in the extract under these conditions. NuMA is dephosphorylated during this assembly process, and the assembly of these NuMA-containing structures is catalyzed by protein dephosphorylation because protein kinase inhibitors enhance their formation and protein phosphatase inhibitors block their formation. Finally, immunodepletion demonstrates that NuMA is an essential structural component of these insoluble particles, and electron microscopy shows that the particles are composed of a complex interconnected network of foci. These results demonstrate that phosphorylation regulates the solubility of NuMA in a mammalian mitotic extract, and the spontaneous assembly of NuMA into extensive structures upon dephosphorylation supports the conclusion that NuMA serves a structural function.

Animals↗
PubMed1996

Molecular cloning of MADM: a catalytically active mammalian disintegrin-metalloprotease expressed in various cell types.

A peptide sequence of a metalloprotease purified from bovine brain [Chantry, Gregson and Glynn (1989) J. Biol. Chem. 264, 21603-21607] was used to design an oligonucleotide probe for screening a bovine brain cDNA library. A contig of the two overlapping cDNA clones that were isolated encoded a 748-amino-acid polypeptide with similarity to the disintegrin-metalloprotease precursor proteins of haemorrhagic snake venom. The bovine protein has been named MADM, for mammalian disintegrin-metalloprotease. The predicted mature protein has 534 amino acids arrayed as extracellular metallo-protease and disintegrin (potential integrin-binding) domains, a transmembrane helix and a basic/proline-rich cytoplasmic C-terminus. Highly conserved homologues of bovine MADM were found in cDNA libraries of rat brain and a human U937 histiocytic lymphoma cell line. A wide variety of mammalian cell lines expressed low levels of MADM mRNA (4.5 and 3.2 kb transcripts) and mature polypeptide (M(r) 62000), as assessed by Northern analysis and Western blotting with an antiserum raised to a peptide within the disintegrin domain. MADM appears to be a rather distantly related member of the reprolysin protein family, which includes both the snake venom disintegrin-metalloproteases and a number of predicted cell-surface disintegrin-containing mammalian proteins.

Amino Acid Sequence↗
PubMed1996

Mutation of the hMSH2 gene in two families with hereditary nonpolyposis colorectal cancer.

We examined 18 unrelated individuals who have colorectal cancer or cancers associated with the HNPCC syndrome and have a family history of cancer for mutations in exon 13 of the hMSH2 gene. Two of the 18 individuals had the same previously unreported single-base deletion in codon 705 of hMSH2, resulting in a frame-shift mutation. Two other individuals had a T-to-C base change in the intron sequence at -6 position of the splice acceptor site at the 5' end of exon 13 which has previously been reported to be a polymorphism found in normal individuals (Leach et al., 1993). Nucleotide sequence changes were not detected in the remaining 14 individuals. We examined DNA from additional family members of the two subjects with codon 705 mutations. Of these, two individuals were identified with the mutation who were older than 50 years and who are apparently cancer free. The occurrence of breast cancer in both families (including one individual with a confirmed codon 705 mutation) suggests that breast cancer may be a part of the HNPCC syndrome. This is the first study to describe mutations in the hMSH2 gene in families that do not fit the definition of HNPCC. Because both families with the mutations at codon 705 failed to meet the Amsterdam criteria for HNPCC (Vasen et al., Dis Colon Rectum 34:424-425, 1991), our findings suggest that these criteria should now be reconsidered for purposes of diagnosis of HNPCC.

Adult↗
PubMed1996

Establishing an interdisciplinary patient care team: collaboration at the bedside and beyond.

The authors describe how an interdisciplinary team used skills in communication and collaboration to improve patient care on a busy surgical service. A major goal was to establish and maintain continuity of care in the face of decreasing lengths of stay and increasing patient acuity. The authors share their insight about designing and supporting a successful interdisciplinary patient care team and discuss how their experiences relate to concepts such as case management and career development.

Communication↗
PubMed1996

NuMA assembles into an extensive filamentous structure when expressed in the cell cytoplasm.

NuMA is a 236 kDa protein that participates in the organization of the mitotic spindle despite its strict localization in the nucleus during interphase. To test how cells progress through mitosis when NuMA is localized in the cytoplasm instead of the nucleus, we have deleted the nuclear localization sequence of NuMA using site-directed mutagenesis and transiently expressed this mutant protein (NuMA-DeltaNLS) in BHK-21 cells. During interphase, NuMA-DeltaNLS accumulates in the cytoplasm as a large mass approximately the same size as the cell nucleus. When cells enter mitosis, NuMA-DeltaNLS associates normally with the mitotic spindle without causing any apparent deleterious effects on the progression of mitosis. Examination of the cytoplasmic mass formed by NuMA-DeltaNLS using transmission electron microscopy (TEM) revealed an extensive network of approximately 5 nm filaments that are further organized by the presence of dynamic microtubules into a dense web of solid, approximately 23 nm cables. Using flow cytometry, we have isolated the intact filamentous mass formed by NuMA-DeltaNLS from lysates of transiently transfected cells. These isolated structures are constructed of networks of interconnected 5 nm filaments and are composed exclusively of NuMA. These data demonstrate that NuMA is capable of assembling into an extensive filamentous structure supporting the possibility that NuMA serves a structural function either in the nucleus during interphase or at the polar ends of the mitotic spindle.

Animals↗
PubMed1995

Current use and clinical outcome of home parenteral and enteral nutrition therapies in the United States.

BACKGROUND & AIMS: Home nutrition support, especially when delivered parenterally, is very costly. The aim of this study is to examine current usage of home parenteral and enteral nutrition (HPEN) in the United States and the quality of therapy outcome. METHODS: Medicare HPEN use from 1989 to 1992 was analyzed to assess use, growth, and costs. National Registry information collected on 9288 patients treated with HPEN from 1985 to 1992 was used to assess disease distribution and therapy outcome. RESULTS: In the United States, there were approximately 40,000 parenteral and 152,000 enteral home patients in 1992. The usage of HPEN doubled between 1989 and 1992, and a large proportion was in patients with short survival. The prevalence of HPEN in the United States was 4-10 times higher than in other Western countries. Outcome data showed both therapies were relatively safe. The primary disease strongly influenced survival and rehabilitation, and age, per se, was not a reason to deny HPEN. CONCLUSIONS: Predicted quality survival at home for several months, rather than a specific diagnosis, seems to be the soundest justification for HPEN. Its role in terminal conditions and patients without primary gastrointestinal diseases needs further evaluations.

Adolescent↗
PubMed1994

Psychiatric outcome in alcoholic liver transplant patients.

We investigated drinking behaviour and psychiatric outcome of patients with alcoholic liver disease after liver transplantation, to help assess the advisability of the procedure in these patients. English-speaking patients (n = 20) transplanted for alcoholic liver disease and informants, and patients transplanted for non-alcoholic liver disease (n = 54), were assessed by semi-structured interviews and standardized questionnaires 1-6 years following transplantation. All alcoholics were abstinent for several months after transplantation, but only one patient remained totally abstinent. Sixteen of the 20 alcoholics later returned to regular drinking; the mean daily alcohol consumption was 3.5 units. Forty percent of the group were drinking above the recommended safe levels for the general population and over 50% were 'binge' drinking intermittently. The alcoholic liver transplant patients did not have higher levels of psychiatric or physical morbidity than controls. Patients with alcoholic liver disease return to drinking after a period of abstinence following liver transplantation, although at lower levels than before. Their vulnerability to alcohol abuse is not explained by higher levels of physical or psychiatric morbidity.

Adult↗
PubMed1993

Home parenteral and enteral nutrition in cancer patients.

The clinical outcomes of 2968 patients with active cancer receiving home nutrition support are described. Of these patients 1672 were receiving home parenteral nutrition and 1296 were receiving home enteral nutrition. The outcomes of these active cancer patients are compared to those of 123 radiation enteritis ("cured" cancer) and 480 Crohn's disease patients receiving home parenteral nutrition and 918 noncancer dysphagic patients receiving home enteral nutrition. This longitudinal clinical information was reported to the North American Home Parenteral and Enteral Nutrition Patient Registry between 1985 and 1990. Evidence indicates that the number of home parenteral and enteral nutrition patients has increased nationally by about 25% each year between 1989 and 1990. In a subsample of 37 home nutrition support programs that have consistently reported their data to the registry since 1985, more than 90% of their program growth was accounted for by new patients with active cancer. This is now the largest single diagnosis of patients starting home parenteral and enteral nutrition. The mean survival time of cancer patients is 6 months after starting home parenteral and enteral nutrition, but 25% live beyond a year and 20% resume full oral nutrition. Although most active cancer patients experience only partial rehabilitation, for those patients with longer survival, rehabilitation is more complete. The outcome is relatively better for children and for patients whose neoplasm is leukemia, lymphoma, small bowel, or liver. In comparison, 96% of home parenteral nutrition Crohn's patients, 80% of home parenteral nutrition radiation enteritis patients, and 60% of home enteral nutrition noncancer dysphagic patients survive at least 1 year. Adult active cancer home parenteral and enteral nutrition patients do not have a greater incidence of therapy-related readmissions than other patient groups, however, their overall rehospitalization rate is much more frequent. This article discusses factors that may have contributed to this growth in home nutrition support in active cancer patients. It attempts to clarify where this therapy is clearly justified and where more information is needed. It emphasizes some of the special issues that need to be addressed in treating these vulnerable patients.

Enteral Nutrition↗