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K Collins

Publications and source records attributed to K Collins.

At least 37 records · Page 2Linked to original sources
PubMed1995

Interleukin-2 receptor expression and function following thermal injury.

BACKGROUND/OBJECTIVE: Serious traumatic or thermal injury is associated with depression of cellular immunity, including the failure of T-lymphocyte proliferation in response to stimulation that depends both on production of interleukin-2 (IL-2) and on expression of functional IL-2 receptors (IL-2R). While decreased IL-2 production following thermal injury is undisputed, the status of IL-2R expression and function in this setting is controversial; therefore, we sought to investigate this issue. DESIGN: A total of 220 male A/J mice (n = 22 per group) were subjected to a 20% scald burn injury or sham burn, killed 4, 7, 10, 14, or 21 days later, and splenocytes harvested. In vitro parameters of both IL-2R expression and function were measured. RESULTS: On day 7, splenic lymphocyte proliferation and IL-2 production in response to mitogenic stimulation were both suppressed following burn injury to 50% and 60% of controls, respectively. Northern blot analysis revealed normal IL-2R p55 messenger RNA expression in response to mitogenic stimulation on days 7, 10, and 14 in thermally injured animals. Phenotypic IL-2R p55 expression in concanavalin A-stimulated CD3+ cells was unchanged following burn injury. Binding of fluorescein-labeled IL-2 to cell membranes was increased in burned animals at days 10 and 14. The addition of IL-2 to cultures of spleen cells from burned mice consistently restored the mitogenic response to that of the controls. CONCLUSIONS: Thermal injury in this model does not result in either quantitative or functional suppression of IL-2R. Suppression of T-cell activation and proliferation, seen following thermal injury, appears primarily related to abnormal IL-2 production.

Animals↗
PubMed1995

Granulocyte-macrophage colony-stimulating factor modulates immune function and improves survival after experimental thermal injury.

Thermal injury is associated with reduced colony-stimulating activity, which correlates with increased susceptibility to infection. To assess the effect of therapeutic administration of granulocyte-macrophage colony-stimulating factor (GM-CSF), 8-week old anaesthetized mice were subjected to either a 20 per cent body surface burn or a sham burn. Animals were subsequently treated with either vehicle or a range of doses of GM-CSF (10-1000 ng) with or without indomethacin (5 micrograms). Sepsis was induced by caecal ligation and puncture on day 10 after injury. Survival was significantly better in animals treated with 200 ng GM-CSF on days 5-9 after the burn. Concanavalin A-stimulated T cell proliferation and interleukin (IL) 2 production were significantly depressed after burn injury. In vivo therapy with 200 ng GM-CSF, however, led to a significant improvement in both of these parameters of T cell function. These data suggest that GM-CSF has a potential therapeutic role in the prevention of death from burn sepsis and appears to act, at least in part, by restoring defective T cell proliferation and IL-2 production.

Animals↗
PubMed1995

Recombinant expression of the brush border myosin I heavy chain.

Although the specific functions of myosin I motors are not known, their localization to membrane structures suggests a function in membrane motility. Different myosin I isoforms in the same cell or in different cells can possess different localizations. To determine if the localization and biochemical activity of the best-characterized mammalian myosin I, chicken intestinal epithelium brush border myosin I, was dependent on determinants of the membrane or actin cytoskeleton specific to epithelial cells, we transfected the cDNA for the heavy chain of this myosin into COS cells. Transient transfection of COS cells with the chicken brush border myosin heavy chain resulted in the production of recombinant myosin I. Recombinant brush border myosin I localized to protrusions of the plasma membrane, particularly at spreading edges, and also to unknown cytoplasmic structures. Some cells expressing particularly high levels of brush border myosin I possessed a highly irregular surface. Recombinant brush border myosin I purified from COS cells bound to actin filaments in an ATP-dependent manner and decorated actin filaments to form a characteristic appearance. The recombinant myosin also catalyzed calcium-sensitive, actin-activated MgATPase activity similar to that of the native enzyme. Thus, any cellular factor required for the general membrane localization or biochemical activity of brush border myosin I is present in COS cells as well as intestinal epithelium.

Actins↗
PubMed1995

Long-term immunotherapeutic intervention with pentoxifylline in a mouse model of thermal injury and infection.

Major thermal or traumatic injury often results in abnormalities of immune function, and these abnormalities contribute to the increased susceptibility to infection observed in these patients. Abnormalities of T-cell function, including decreased proliferation and secretion of cytokines are observed following major injury and, conversely, there is markedly increased monokine production. Thus, therapy of this syndrome might logically be aimed at modulating the immune system to upregulate T-cell function and downregulate monocyte hyperactivation. Pentoxifylline (PTX), a methylxanthine derivative, has been shown to be therapeutically effective in several animal models. The purpose of this study was to evaluate PTX and its effect on cytokine production in a mouse model of thermal injury and to study its effect on survival after septic challenge. The results show that PTX therapy after injury can restore T-cell production of IL-2 and downregulate the hyperactive macrophage secretion of proinflammatory cytokines. However, improvement in survival resulting from this therapy following thermal injury and septic challenge depends on timing of dosage.

Animals↗
PubMed1995

Multiple system organ failure may be influenced by macrophage hypoactivation as well as hyperactivation--importance of the double challenge.

OBJECTIVE: To find out if an infective challenge caused by a burn followed by caecal ligation and puncture in mice caused more abnormalities of the immune response than burn alone or caecal ligation and puncture alone. DESIGN: Laboratory study. SETTING: University hospital, USA. MATERIAL: 80 male 7-8 week old A/J mice. INTERVENTIONS: Burn followed 10 days later by caecal ligation and puncture (n = 18), caecal ligation and puncture alone (n = 24), burn alone (n = 20), and controls (n = 18). The mice had their spleens removed on day 11 (n = 28; 6, 8, 8, and 6 in the respective groups), day 12 (n = 26; 6, 8, 6, and 6), and day 13 (n = 26; 6, 8, 6, and 6), and splenocytes and adherent cells were harvested for measurement of prostaglandin E2 (PGE2), interleukin 1 (IL-1), interleukin 2 (IL-2), interleukin 6 (IL-6), and tumour necrosis factor alpha (TNF-alpha). MAIN OUTCOME MEASURES: Alterations in the production of the cytokines. RESULTS: After the double challenge (burn followed by caecal ligation and puncture) there were significant reductions in production of TNF-alpha and IL-6 compared with caecal ligation and puncture alone (p < 0.05), burn alone (p < 0.05), and controls (p < 0.05). These findings indicate that activation of macrophages was reduced after infection; production of TNF-alpha, IL-1, and IL-6 by splenocytes stimulated by lipopolysaccharide was reduced. CONCLUSIONS: The differences do not seem big enough to indicate that mortality would be increased after caecal ligation and puncture alone. Only when there has been a previous injury (which resulted in hyperactivation of macrophages followed by a more pronounced hypoactivation) would mortality increase. In view of clinical trials with antiendotoxin and antiTNF antibodies that failed to improve survival in infected patients, we suggest that the mechanisms of the cellular immune response need further clarification.

Animals↗
PubMed1994

Innovations in case flow analysis: using midlier variance analysis.

This article presents the use of midlier and case flow analysis during a retrospective chart review to study the costs of hospital length of stay. The results showed that considerable savings can be realized by using these methods for one group of patients with the same diagnosis. We were able to redefine and track patients during their pre-, peri-, and postoperative period and estimated the time and cost opportunities for work flow improvement. We concluded that considerable savings are possible by extending the analysis to patients in other DRG groups.

Analysis of Variance↗
PubMed1993

Mechanism of increased tumor necrosis factor production after thermal injury. Altered sensitivity to PGE2 and immunomodulation with indomethacin.

Altered macrophage function after thermal injury is associated with increased production of PGE2 and TNF. However, it is not clear why synthesis of both cellular products remains elevated, as PGE2 is a potent inhibitor of TNF secretion. We studied the relationship between PGE2 and TNF synthesis in a murine model of thermal injury, and examined the effect of prostaglandin blockade on splenic macrophage secretion of these mediators of inflammation. LPS-stimulated production of PGE2 was significantly elevated in burn groups compared with sham-burned controls (pg/ml mean(SEM); sham 151(32): burn 597(147), p < 0.01). TNF production was similarly increased after thermal injury (pg/ml mean(SEM); sham 62(20): burn 928(316), p < 0.01). In vitro culture of macrophages with indomethacin augmented LPS stimulated TNF production in sham-burned controls but did not affect synthesis in burn groups, suggesting a loss of PGE2-dependent regulation of TNF synthesis after thermal injury. Direct measurement of TNF secretion as a function of exogenous PGE2 confirmed this dissociation between PGE2 and TNF synthesis, as burned animals displayed a 5-fold reduction in sensitivity to PGE2-induced inhibition of TNF, when compared with sham-burned controls (ID50 PGE2 molar; sham 1.26 x 10(-8): burn 6.43 x 10(-8), p < 0.05). In vivo pretreatment of burn groups with indomethacin for 5 days before assay partially restored sensitivity to the prostaglandin, and significantly down-regulated synthesis of both TNF and PGE2. These data show that thermal injury is associated with a loss of PGE2-dependent down-regulation of TNF synthesis, which accounts at least in part for increased TNF in these animals. In vivo cyclooxygenase blockade partially restored sensitivity to the prostaglandin and consequently down-regulated synthesis of TNF. These data further support existing evidence that suggests a potential therapeutic role for cyclooxygenase blockade after major thermal injury and trauma.

Animals↗
PubMed1993

Stage-related changes in steroid-converting enzyme activities in Squalus testis: synthesis of biologically active metabolites via 3 beta-hydroxysteroid dehydrogenase/isomerase and 5 alpha-reductase.

To investigate the relationship between steroidogenesis and spermatogenesis, two key enzymes of androgen biosynthesis, 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) and 5 alpha-reductase, were compared at premeiotic (PrM), meiotic (M), and postmeiotic (PoM) stages. Staged tissues were obtained by dissection from the testis of the spiny dogfish Squalus acanthias, in which spermatogenesis is a simple diametric progression. Microsomal 3 beta-HSD activity was measured by conversion of [3H]dehydroepiandrosterone (DHEA) to androstenedione (AE). Reaction constants were: Km = 3.2 microM and Vmax = 243 pmol/min/mg protein. 3 beta-HSD increased progressively with maturation, resulting in three- to four-fold higher levels in PoM than in PrM stages. Absolute values and stage-related differences were the same, whether microsomes were derived from whole testis or from isolated spermatocysts (germ cell/Sertoli cell units), thus supporting microscopic studies showing that Sertoli cells are the primary steroidogenic elements of dogfish testis. In vitro conversion of [3H]testosterone to [3H]dihydrotestosterone (DHT) was used to estimate 5 alpha-reductase activity. Apparent substrate affinity was similar to that of 3 beta-HSD (Km = 2.9 microM), but maximal product yields were two to three orders of magnitude lower (Vmax = 208 fmol/min/mg protein). Also, the stage-related pattern of 5 alpha-reductase activity (PrM > PoM >> M) differed from that of 3 beta-HSD (PoM >> M > PrM).(ABSTRACT TRUNCATED AT 250 WORDS)

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1993

Relative distribution of actin, myosin I, and myosin II during the wound healing response of fibroblasts.

Myosin I is present in Swiss 3T3 fibroblasts and its localization reflects a possible involvement in the extension and/or retraction of protrusions at the leading edge of locomoting cells and the transport of vesicles, but not in the contraction of stress fibers or transverse fibers. An affinity-purified polyclonal antibody to brush border myosin I colocalizes with a polypeptide of 120 kD in fibroblast extracts. Within initial protrusions of polarized, migrating fibroblasts, myosin I exhibits a punctate distribution, whereas actin is diffuse and myosin II is absent. Myosin I also exists in linear arrays parallel to the direction of migration in filopodia and microspikes, established protrusions, and within the leading lamellae of migrating cells. Myosin II and actin colocalize along transverse fibers in the lamellae of migrating cells, while myosin I displays no definitive organization along these fibers. During contractions of actin-based fibers, myosin II is concentrated in the center of the cell, while the distribution of myosin I does not change. Thus, myosin I is found at the correct location and time to be involved in the extension and/or retraction of protrusions and the transport of vesicles. Myosin II-based contractions in more posterior cellular regions could generate forces to separate cells, maintain a polarized cell shape, maintain the direction of locomotion, maximize the rate of locomotion, and/or aid in the delivery of cytoskeletal/contractile subunits to the leading edge.

3T3 Cells↗
PubMed1993

Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation.

Telomerase is a ribonucleoprotein enzyme that adds telomeric repeats to chromosomes, maintaining telomere length and stabilizing chromosome ends. In vitro, telomerase from the ciliate Tetrahymena elongates single-stranded, guanosine-rich DNA primers by adding repeats of the Tetrahymena telomeric sequence, dT2G4. We have identified two activities of Tetrahymena telomerase in addition to the previously described processive elongation reaction: a 3'-5' nucleolytic cleavage of primer or product DNA and a nonprocessive mode of elongation. The nucleolytic cleavage activity removed residues not conforming to the telomeric repeat sequence from a primer 3' end, eliminating mismatch between DNA primer and RNA template sequences. Template-matched residues were also cleaved from primer or product DNA. Specific primer lengths, sequences, and concentrations stimulated cleavage and processive or nonprocessive elongation differentially. These newly identified activities suggest that telomerase may catalyze a range of telomere synthesis and repair functions and suggest mechanistic similarities between telomerase and RNA polymerase enzymes. On the basis of our results, we propose a model for telomerase primer binding, cleavage, and elongation.

Animals↗
PubMed1993

Molecular mechanisms of decreased interleukin-2 production after thermal injury.

BACKGROUND: Among the fundamental immunologic abnormalities induced by serious traumatic or thermal injury are alterations in T cell activation, reduced lymphocyte interleukin-2 (IL-2) production, and associated depression of T lymphocyte proliferation. This study attempts to localize the cellular mechanisms underlying abnormal IL-2 production in thermal injury. METHODS: Following National Institutes of Health guidelines, 150 A/J mice were anesthetized, subjected to a 20% full-thickness scald burn injury or sham burn, and killed at intervals from 4 to 21 days later; splenocytes were harvested for in vitro studies. For measurement of IL-2 production, cells were cultured with either concanavalin A or a combination of the phorbol ester PMA, which directly activates protein kinase C, and the calcium ionophore A23187, which increases intracellular calcium. Cytokine mRNA expression was measured by Northern blot analysis and IL-2 production by bioassay. RESULTS: Both IL-2 production and IL-2 mRNA expression were consistently suppressed in concanavalin A-stimulated cells from burned mice compared with sham burns. This suppression of IL-2 and IL-2 mRNA also occurred when T cells were activated with PMA and A23187, bypassing the earlier stages of the signal transduction mechanism. IL-1 beta and tumor necrosis factor-alpha mRNA expression were consistently increased in burned animals, indicating that decreased IL-2 mRNA expression was specific to IL-2 and not representative of a global decrease in cytokine mRNA expression. CONCLUSIONS: These results suggest that the principal cellular abnormalities that result in altered T cell activation and IL-2 production after thermal injury lie downstream of the initiating signal transduction events and before IL-2 gene transcription.

Animals↗
PubMed1992

Expression and localization of villin, fimbrin, and myosin I in differentiating mouse F9 teratocarcinoma cells.

F9 embryonic carcinoma cells are a multipotent cell line which can be induced to differentiate into cells resembling the visceral endoderm, an extraembryonic absorptive epithelium characterized by apical microvilli. We have examined the role of villin, fimbrin, and myosin I, the major actin-binding proteins in the intestinal and visceral yolk sac microvilli, in the development of epithelial polarity and the assembly of the microvillus cytoskeleton in differentiating F9 cells. By immunoblot analysis villin was first detected at 4 days of differentiation. Confocal microscopy localized villin at Day 4 to the apical surface and by Day 6 to the basolateral surfaces as well. In comparison, fimbrin and myosin I were both present in undifferentiated F9 cells and became associated with the apical surface after villin during differentiation to visceral endoderm. The accumulation of villin, fimbrin, and myosin I at the apical surface in differentiating F9 cells correlated with the appearance of microvilli containing organized actin filament bundles. Two mouse villin cDNAs were isolated and characterized to examine villin expression during F9 differentiation. Mouse villin was encoded by two transcripts (3.8 and 3.4 kb) which differ in their 3'-noncoding region. Both villin mRNAs were first detected by Day 4 of differentiation and their appearance coincided with expression of the visceral endoderm marker alpha-fetoprotein. The pattern of expression and order of accumulation of villin, fimbrin, and myosin I in differentiating F9 cells are common to developing gut and yolk sac epithelium. This suggests that microvillus assembly is directed by a sequence of temporally and spatially regulated localizations of these actin-binding proteins.

Animals↗
PubMed1992

Changing trends in explanted intraocular lenses: a single center study.

Over a nine-year period, our practice removed 1,091 intraocular lenses. The most common type of lens requiring explantation was the closed-loop anterior chamber lens (58.6%). The Stableflex lens represented the largest percentage of all removed lens types (28.8%). The number of closed-loop anterior chamber lenses requiring removal peaked in 1988 and then gradually declined. All other lens styles have shown gradually increasing removal rates. Older style iris-fixated lenses and rigid anterior chamber lenses, which have not been implanted for several years, have increasing removal rates. Late breakage of fixational polypropylene sutures with pupil-supported iris-fixated lenses have occurred in five cases; the average time from implantation to suture breakage was 112 months.

Anterior Chamber↗
PubMed1992

Explantation of posterior chamber lenses.

A consecutive series of 119 explanted posterior chamber lenses is reviewed. Seventy (58.8%) were removed because of dislocation or improper fixation, 15 (12.6%) because of anisometropia, and 18 (15.1%) because of chronic inflammation. Sixty-two (52.1%) of these explantations probably occurred for reasons that can be avoided by changes in preoperative, operative, or postoperative techniques. The rate of posterior chamber lens explantations is quite low considering the large number of lenses implanted; with changing surgical techniques, we anticipate that the number of lenses requiring removal will decrease.

Aged↗
PubMed1992

Suppressor T-cell levels are unreliable indicators of the impaired immune response following thermal injury.

The presence of increased levels of suppressor T cells after thermal injury and their relevance remain controversial. It is unclear whether suppressor T cells are the cause or result of sepsis complicating thermal injury. Spleen cells from a standardized murine burn model and sham burn controls were studied and the relationship between the levels of suppressor cytotoxic T cells (CD8, Lyt-2+), helper T cells (CD4, L3T4+), response to concanavalin A (ConA) and to phytohemagglutinin (PHA) and interleukin-2 (IL-2) production was examined. Mortality following infection via cecal ligation and puncture (CLP) of matched controls was also studied. At day 7 postburn, mean ConA (70 +/- 12% of control) and PHA response (58% +/- 5.2% of controls) and IL-2 production (43% +/- 5.4%) were significantly less than sham burn values (100%; p less than 0.05). However, the mean percentage of cells staining with anti-Lyt-2 and anti-L3T4 (9.1 +/- 0.59 and 13.9 +/- 0.65) was similar to the mean percentage in sham burn animals (9.4 +/- 0.65 and 16.6 +/- 1.1). Furthermore, no significant differences were observed between burned mice and controls in helper (17.3% +/- 1.8% burn vs. 21.2% +/- 1.7% sham) or suppressor cell levels (7.8% +/- 1.2% burn vs. 8.6% +/- 0.7% sham) or helper-suppressor ratios on day 10 postburn. Mortality of 20 litter-matched controls subjected to CLP on day 10 postburn was 90%, which was significantly greater than the sham burn mortality of 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗