PubMed Health⌕ Search

Biomedical subjects

S Perkins

Publications and source records attributed to S Perkins.

At least 19 recordsLinked to original sources
PubMed1996

A gene map of the human genome.

The human genome is thought to harbor 50,000 to 100,000 genes, of which about half have been sampled to date in the form of expressed sequence tags. An international consortium was organized to develop and map gene-based sequence tagged site markers on a set of two radiation hybrid panels and a yeast artificial chromosome library. More than 16,000 human genes have been mapped relative to a framework map that contains about 1000 polymorphic genetic markers. The gene map unifies the existing genetic and physical maps with the nucleotide and protein sequence databases in a fashion that should speed the discovery of genes underlying inherited human disease. The integrated resource is available through a site on the World Wide Web at http://www.ncbi.nlm.nih.gov/SCIENCE96/.

Amino Acid Sequence↗
PubMed1996

Local immune response in Helicobacter pylori-infected cats and identification of H. pylori in saliva, gastric fluid and faeces.

Helicobacter pylori-infected cats were screened by culture and polymerase chain reaction (PCR) for the presence of H. pylori in salivary secretions, gastric juice, gastric tissue and faeces. H. pylori was cultured from salivary secretions in six of 12 (50%) cats and from gastric fluid samples in 11 of 12 (91%) cats. A 298 base pair polymerase chain reactions (PCR) product specific for an H. pylori 26000 MW surface protein was amplified from dental plaque samples from five of 12 (42%) cats and from the faeces of four of five (80%) cats studied. Analyses of serum and mucosal secretions by enzyme-linked immunosorbent assay (ELISA) revealed an H. pylori-specific immunoglobulin G (IgG) response, and elevated IgA anti-H. pylori antibody levels in salivary and local gastric secretions. Immunohistochemical analyses of gastric tissue revealed the presence of IgM+ B cells assembled into multiple lymphoid follicles surrounded by clusters of CD4+ and CD8+ T cells. The lamina propria also contained single cells or aggregates of IgA+ and IgM+ B cells. These observations show that H. pylori can be identified in feline mucosal secretions, and that a localized IgA immune response develops in gastric tissue of H. pylori-infected cats. The findings suggest a zoonotic risk from exposure to personnel handling H. pylori-infected cats in vivaria.

Animals↗
PubMed1996

A source of glycosylated human T-cell lymphotropic virus type 1 envelope protein: expression of gp46 by the vaccinia virus/T7 polymerase system.

Heterologous expression of the human T-cell lymphotropic virus type 1 (HTLV-1) envelope surface glycoprotein (gp46) in a vaccinia virus/T7 polymerase system resulted in the production of authentic recombinant gp46. Five differentially glycosylated forms of the surface envelope protein were produced by this mammalian system, as demonstrated by tunicamycin inhibition of N-glycosylation and N-glycan removal with endoglycosidase H and glycopeptidase F. These studies revealed that all four potential N-glycosylation sites in gp46 were used for oligosaccharide modification and that the oligosaccharides were mannose-rich and/or hybrid in composition. Conformational integrity of the recombinant HTLV-1 envelope protein was determined by the ability to bind to various HTLV-1-infected human sera and a panel of conformational-dependent human monoclonal antibodies under nondenaturing conditions. Furthermore, this recombinant gp46 was recognized by a series of HTLV-2-infected human sera and sera from a Pan paniscus chimpanzee infected with the distantly related simian T-cell lymphotropic virus STLVpan-p. Maintenance of highly conserved conformational epitopes in the recombinant HTLV-1 envelope protein structure suggests that it may serve as a useful diagnostic reagent and an effective vaccine candidate.

Animals↗
PubMed1996

[Hemocompatibility testing of polymers].

Haemoincompatibility induced by contact with artificial materials is a major obstacle to further development of artificial organs and accounts for much of morbidity in circumstances when the blood is circulated through an extracorporeal system or a catheter is placed. Material's testing was performed using different models and a score system (0-60 scorepoints) was developed. Our models can characterize ex vivo haemocompatibility of different polymers. Flow characteristics and preanalytical effects (e.g. anticoagulants) may not be neglected.

Blood Banks↗
PubMed1995

Delineation of an immunodominant and human T-cell lymphotropic virus (HTLV)-specific epitope within the HTLV-I transmembrane glycoprotein.

Antibody reactivity to the transmembrane region of human T-cell lymphotropic virus type I (HTLV-I) envelope, gp21, is observed in virtually all individuals infected with HTLV-I or HTLV-II. Recombinant proteins encoding selected portions of gp21 are described and used to define two immunogenic regions. The first epitope (designated GD21-I) contains amino acids 361 to 404 of the HTLV-I envelope and reacted with all of 54 sera from HTLV-I- and HTLV-II-infected individuals. The second epitope (designated BA21) expresses amino acids 397 to 430 of the HTLV-I envelope and was recognized by 33 of 54 HTLV antisera. To determine the specificity of GD21-I and BA21, sera from 17 HTLV-negative individuals with nonspecific reactivity to p21E were tested. None of these sera reacted with GD21-I, but 16 of 17 sera reacted with BA21. With virtually complete reactivity to sera from HTLV-infected individuals and no reactivity to sera from p21E-reactive uninfected individuals, GD21-I will be useful in immunoassays for the detection of HTLV infection.

Amino Acid Sequence↗
PubMed1995

A new data model for biological classification.

In the domain of biological classification, classifications are performed hierarchically. There are no standard classifications which are unanimously accepted by the community of each domain; many different interacting views of classification exist about the same data, and the discovery of new data results in changes to the existing classification. Even a single individual may change his or her own classification of a particular group. Since multiple classification views interact, they are semantically related. It is difficult to model this kind of dynamically evolving and semantically interacting classification system using traditional data models, which lack the structural flexibility necessary to support dynamic views of hierarchic classifications, and cannot properly capture the history of these complex interactions. We have developed a new data model which is suitable for supporting semantically interacting dynamic views of hierarchic biological classifications. On the basis of our new data model we have developed a prototype database system called HICLAS (HIerarchical CLAssification System); its domain is plant taxonomy. HICLAS is available through the Internet and an X-window interface has been implemented to support queries to classification data.

Classification↗
PubMed1995

Isolation of endothelial-like stromal cells that express Kit ligand and support in vitro hematopoiesis.

Although macrophages account for 70-90% of the adherent cells in mouse long-term bone marrow cultures (LTBMC) and CFU-F colonies, the predominant nonhematopoietic stromal cell is endothelial-like (EL), expressing cytoplasmic collagen IV, laminin, and an antigen recognized by the monoclonal antibody MECA-10. We report the isolation of this stromal cell lineage from primary LTBMC by immunomagnetic cell selection using MECA-10. More than 95% of the cells in the MECA-10-positive fraction are EL cells as judged by morphology, surface staining for MECA-10, cytoplasmic staining for collagen IV, and electrophoretic analysis of MECA-10-positive cells isolated from radiation chimeras. When plated under LTBMC conditions, EL cell monolayers recharged with either wild-type or Sl/Sld marrow support an increased density and number of clonogenic and mature hematopoietic cells in short-term cultures. In accord with this finding, Northern blots of mRNA from unstimulated EL cells demonstrate constitutive expression of Kit ligand (KL). Moreover, in situ two-color immunofluorescence staining for cytoplasmic collagen IV and surface KL suggests that EL cells are the exclusive source of membrane-bound KL in mouse cultures. The ability to isolate EL cells from primary cultures without the need for repeated cell passage or immortalization provides a novel approach to dissecting the molecular basis of stem cell-stromal cell interactions.

Animals↗
PubMed1995

Age-related bone loss. A hypothesis and initial assessment in mice.

The osteopenia associated with advanced age appears to be a universal phenomenon in humans and animals, but the mechanisms by which it occurs are understood incompletely. However, the explanation must lie in an absolute or relative diminution in the level of osteoblastic bone-forming activity when compared with osteoclastic bone-resorbing activity. The authors postulated that with old age there would be a reduction in the number or function or both of osteoblastic stem cells that could account for part of the diminution in bone formation. They further postulated that there would be either no change or an increase in osteoclastic potential and bone resorption. To test these concepts, bone marrow cells were isolated from 4- to 6-month-old or 24-month-old mice and cultured in vitro under a variety of circumstances that permitted an assessment of the stromal osteogenic cells and marrow hemopoietic progenitor cells belonging to the monocyte and osteoclast series. These data show a marked reduction in the number and in vitro activity of stromal osteogenic cells from old animals. There is an increase in old mice in the number of marrow cells capable of forming osteoclasts in coculture and responsive to the growth factors believed operational in the monocyte and osteoclast series. The authors now are exploring the hypothesis that an age-related diminution in transforming growth factor-beta levels is responsible for these changes in progenitor cell levels in marrow and their functional status as expressed in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1995

Absenteeism in acute care hospitals.

Lack of standardization in formulas for calculating absenteeism impeded comparison among institutions and comparison to rates reported for the health care industry. Even though illness related benefits, replacement costs for absent employees and attendance incentives absorbed scarce financial resources, more than 40% of hospitals had no standard for excessive absence. Directors of nursing were concerned about staffing and the possibility that employees were tiring to the point of becoming ill. Among directors, concern about absenteeism was greatest in urban hospitals of 100-200 beds.

Absenteeism↗
PubMed1994

Localization of antigenic sites on human cytomegalovirus virion structural proteins encoded by UL48 and UL56.

Two human cytomegalovirus (HCMV) virion structural proteins and their associated reading frames have been identified with two human-derived monoclonal antibodies (HMAbs), X2-16 and X-16. HMAb X2-16 identified recombinant protein expressing molecular clones that mapped to the open reading frame (ORF) of the UL48 gene of HCMV, between amino acids 584 and 646 (nucleotides 65,084 and 65,272, Chee et al., 1990, "Current Topics in Microbiology and Immunology," Vol. 154, pp. 125-169). The UL48 gene product has an apparent molecular weight of 216 kDa. HMAb X-16 identified clones derived from the UL56 ORF between amino acids 380 and 425 (nucleotides 84,733 and 84,870). On immunoblots, HMAb X-16 detected two HCMV proteins of 96 and 60 kDa. Both UL48 and UL56 are highly conserved among the human herpesviruses and their products have been predicted to have essential functions for virus production and maturation. These results confirm that UL48 and UL56 are functional genes encoding essential viral proteins which also generate an immune response in the immunocompetent host.

Amino Acid Sequence↗
PubMed1994

Double modulation of 5-fluorouracil in the treatment of advanced colorectal carcinoma: report of a trial with sequential methotrexate, intravenous (loading dose) folinic acid, 5-fluorouracil, and a literature review.

5-Fluorouracil (5-FU) modulation with either folinic acid (FA) or methotrexate (MTX) has improved 5-FU's potential cytoreductivity. We combined MTX and FA with 5-FU to further augment 5-FU's cytoreductivity. Patients (n = 34) with advanced colorectal carcinoma were first given intravenous MTX (escalated from 30 mg/m2 to 70 mg/m2). FA (100 mg/m2) was infused 17-24 hr later, followed by 5-FU (600 mg/m2). Oral rescue doses of FA were begun 24 hr after MTX. Patients were treated every 2 weeks. No previously treated patient (n = 6) responded. Eight of the remaining 28 (29%) (95% confidence interval, 15-47%) patients achieved a PR. Median survival was 9.3 months. Toxicity (primarily gastrointestinal) necessitated dosage modification in 10 patients (29%). These results, in addition to a literature review, reveal that the manipulation of 5-FU by two modulating agents does not improve the response rate seen with single-agent modulation.

Adult↗
PubMed1993

Verapamil prevents chronic renal failure-induced abnormalities in lipid metabolism.

Hypertriglyceridemia is common in chronic renal failure (CRF); this derangement is due to decreased peripheral removal of triglycerides. Certain data indicate that the state of secondary hyperparathyroidism of CRF is, at least in part, responsible for derangements in lipid metabolism. It has been proposed that chronic excess of parathyroid hormone exerts its deleterious effects on many organs through its ability to raise basal levels of cytosolic calcium. Prevention of the latter by a calcium channel blocker is followed by the correction of organ dysfunctions. The present study examined the effect of treatment of CRF rats with verapamil on several parameters of lipid metabolism. Chronic renal failure rats displayed hypertriglyceridemia, fat intolerance, reduced postheparin plasma lipoprotein and hepatic lipase activities, decreased hepatic lipase in liver homogenate, and elevated calcium content in liver and epididymal fat. Treatment of the CRF rats with verapamil prevented all these derangements in lipid metabolism. These effects of verapamil were similar to those produced by parathyroidectomy of CRF rats. The data are consistent with the formulation that chronic excess of parathyroid hormone increases the calcium burden of liver and adipose tissue and consequently impairs the synthesis and/or release of lipoprotein and hepatic lipases. Reduced availability of these enzymes in plasma results in impared peripheral removal of triglycerides, leading to hypertriglyceridemia.

Animals↗
PubMed1992

Twin pregnancy in a patient with complete heart block. A case report.

A 22 year old primigravida with previously undiagnosed congenital complete heart block and a twin gestation is described. Early diagnosis of both problems and cardiac consultation allowed a temporary pacemaker to be inserted early in the third trimester. The patient was delivered by caesarean section at 36 weeks following spontaneous rupture of membranes. Maternal and fetal outcomes were excellent.

Adult↗
PubMed1992

Stem cell quiescence/activation is reversible by serial transplantation and is independent of stromal cell genotype in mouse aggregation chimeras.

We made use of a previously described in vivo model of chimeric mice created by embryo aggregation that allows the study of contributions to both lymphohematopoiesis and marrow stroma by two genotypically distinct cell populations. Day-2 embryos from C57BL/6 and DBA/2 strains were fused to produce allophenic chimeric mice that proved to have contributions from each strain in all the tissues of the body and that permitted study of competitive contributions to blood formation. Although the contribution of DBA/2 stem cells to hematopoiesis gradually ceased in an age-related manner so that all blood cells in aged chimeras were C57BL/6 in origin, here we show that, in contrast, the extent of stromal chimerism, determined by the fibroblast colony-forming unit (CFU-F) assay, was maintained and was remarkably uniform from one marrow site to another. This result is consistent with a polyclonal nonhematopoietic origin of the CFU-F and suggests that the decline in DBA/2 blood cells was not dependent on similar changes in genotype-matched stroma, but was instead an intrinsic property of this stem cell population. These intrinsic stem cell properties were further examined by serial bone marrow transplantation. When marrow from a chimera with no detectable DBA/2 blood cells was transplanted into irradiated recipients, cells of DBA/2 genotype significantly contributed to early hematopoietic engraftment, demonstrating that the DBA/2 stem cell population was not extinguished in the chimeric donor, but rather had entered a reversible state of quiescence. Reactivation of the DBA/2 stem cell population, however, was short-lived, and long-term engraftment of recipients was accomplished by donor cells of the partner strain (C57BL/6). However, transient reactivation of the quiescent (DBA/2) stem cell pool again occurred with a second round of transplantation. These surprising results demonstrate, for the first time, selective and reiterated inactivation and reactivation of a stem cell population depending on hematopoietic needs. Moreover, the results suggest that genetic differences in the stem cell populations of coexistent strains account for the selective responses described.

Age Factors↗
PubMed1991

Parameters to enhance human hybridoma formation with hypoosmolar electrofusion.

Hypoosmolar conditions have permitted the development of electrofusion techniques capable of producing human hybridomas from as few as 10(5) B cells. A hybridoma formation efficiency of one hybrid for each 125 input B cells has been achieved with Epstein-Barr virus--activated B cells and mouse-human heteromyelomas. This is at least 100-fold higher in efficiency than with polyethylene glycol-induced cell fusion, as well as a 50- to 100-fold decrease in the required number of human B cells. The ability to fuse a small number of input B cells should lead to a greater success rate in immortalizing the rare antigen-specific B cells. The critical parameters include fusion voltages, the composition and number of wash steps used in cell preparation, the composition and duration of exposure to hypoosmolar fusion medium, fusion ratio, plating density, the use of growth medium without pH indicator, and the use of an irradiated human fibroblast feeder layer. By manipulating these parameters, a high hybrid yield can be achieved with different mouse-human heteromyelomas and Epstein-Barr virus-activated B cells.

B-Lymphocytes↗
PubMed1990

Development of microfusion techniques to generate human hybridomas.

The rarity of antigen-specific B cells in peripheral blood and lymphoid tissues is a major limitation in the production of human monoclonal antibodies. This has led to a requirement for techniques capable of fusing small numbers of cells and achieving a higher hybridoma formation efficiency than currently is possible. The approach used in these studies to generate human hybridomas is based on the observation that under hypo-osmolar conditions electric field induced cell fusion or electrofusion is facilitated. Electrofusion parameters have been defined in strongly hypo-osmolar solutions which have resulted in a hybridoma formation efficiency greater than 5 X 10(-3) under optimal conditions. Furthermore, this has been accomplished with total input B cells of 1-2 X 10(5). This is a ten-fold reduction in the required number of input B cells and is associated with a hybridoma formation efficiency at least equal to that achieved with a higher input B cell number. An important factor in the development of this microfusion technique appears to be the duration of exposure to the hypo-osmolar solution by B cells to be immortalized. Other parameters which may affect hybridoma yield include the electrical field strength used for cell alignment and membrane breakdown, ratio of human B cells to fusion partner, washing procedure, post-fusion incubation time, and the elimination of toxic molecules.

Antibodies, Monoclonal↗