Biomedical subjects

M Bennett

Publications and source records attributed to M Bennett.

At least 19 recordsLinked to original sources

PubMed1992

Red 25, a protein that binds specifically to the sterol regulatory region in the promoter for 3-hydroxy-3-methylglutaryl-coenzyme A reductase.

A protein that binds to the sterol regulatory region of the hamster promoter for 3-hydroxy-3-methylglutaryl-coenzyme A reductase has been identified. All of the DNA bases crucial to the binding of this protein were previously shown to be essential for sterol regulation of the intact promoter in cultured cells. This low abundance protein, called Red 25, has been purified from nuclear extracts of hamster liver by a series of standard chromatographic techniques coupled with a DNA affinity step. Its size has been estimated as approximately 42 kDa by gel electrophoresis, size exclusion chromatography, and protein-DNA cross-linking studies. Furthermore, it binds to its target site with a Kd = 6 x 10(-11) M. Red 25 does not bind to the sterol regulatory regions of the LDL receptor or 3-hydroxy-3-methylglutaryl-coenzyme A synthase. This is consistent with recent studies that show there is a unique site for sterol regulation in the reductase promoter. The identification and purification of this protein represents a significant step in the study of feedback regulation by cholesterol.

Animals↗

PubMed1992

Donor-type activated natural killer cells promote marrow engraftment and B cell development during allogeneic bone marrow transplantation.

Purified NK cells were obtained from mice with severe combined immune deficiency and were activated with human IL-2 (hrIL-2) in vitro to determine if, once activated, these cells could be transferred with compatible bone marrow cells (BMC) and promote marrow engraftment in irradiated allogeneic recipients. After culture with hrIL-2, these cells maintained a phenotypic and lytic spectrum consistent with a pure population of activated NK cells. These activated NK cells were then adoptively transferred with the donor BMC and rhIL-2 into lethally irradiated allogeneic hosts. The addition of NK cells with the BMC allowed for more rapid hematopoietic engraftment as determined through short term studies, and greater donor-derived chimerism with accelerated reconstitution of the B cell population as determined with long term analysis. No evidence of graft-vs-host disease was detected in the recipients receiving the activated NK cells with allogeneic T cell replete BMC and hrIL-2. The mechanism by which the transferred NK cells improved BMC engraftment was at least partly through the abrogation of the host effector cell's ability to mediate resistance to the marrow graft. Thus, the administration of donor-type activated NK cells with BMC and hrIL-2 may significantly augment hematopoietic engraftment and immune reconstitution in the clinical setting of allogeneic BMT without giving rise to graft-vs-host disease.

Animals↗

PubMed1992

Human-mouse lymphoid chimeras: host-vs.-graft and graft-vs.-host reactions.

Human peripheral blood lymphocytes (huPBL) were injected into mice with severe combined immune deficiency (SCID). It was ascertained that murine natural killer (NK) cells were capable of affecting engraftment of human lymphocytes in SCID mice. The presence of host NK cells resulted in the clearance of the human lymphocytes. Human T lymphocytes were the primary cell to engraft in the SCID recipients, with human T cells being detected in the spleen, lymph nodes, bone marrow and peritoneal cavity of the mice up to several months after transfer. No human T cells were detected in the murine thymus and the level of engraftment in the periphery could be highly variable. Additionally, there appeared to be significant reactions between the human lymphocytes and the murine host resulting in a xenogeneic graft-vs.-host reaction (XGVHR). The predominant manifestation involved splenomegaly resulting from an expansion of murine hematopoietic cells in the spleens of these xenogeneic chimeras. The severity of the XGVHR could be correlated with the extent of human T cell engraftment and the recovered human T cells were found to be in a proliferative state. Thus, there appear to be significant host-vs.-graft and graft-vs.-host interactions occurring in human/mouse lymphocyte chimeras.

Animals↗

PubMed1992

Characterization of orthopoxviruses isolated from feline infections in Britain.

The biological properties and genomes of orthopoxviruses isolated from cats in Britain were compared with strains of cowpox virus isolated from cows and their handlers. All the isolates tested produced haemorrhagic pocks and A-type inclusions on the CAM, but did not produce pocks above 40 degrees C. Thus the feline isolates behaved as typical strains of cowpox virus. Differences were found in the heat resistance of the virions and in the character of the A-type inclusion which did not correlate with the host from which the viruses were isolated. Analysis of the genomes with a variety of restriction endonucleases showed very close relationship between all the isolates and also failed to separate feline isolates from cowpox virus. However again minor differences, which may prove to be of epidemiological value were detected. We conclude that the orthopoxvirus currently isolated from domestic cats in Britain is cowpox virus and that there is no evidence that a feline variant or subspecies circulates in Britain.

Animals↗

PubMed1992

Identification and sequence determination of the capsid protein gene of feline calicivirus.

We have determined 4380 bases of the sequence from a cDNA clone containing the 3' end of feline calicivirus strain F9. We find four candidate open reading frames of which three are complete and comprise 245, 317 and 2012 nucleotides. The fourth continues toward the 5' end. We have expressed the largest complete open reading frame in E. coli. Sera raised to this antigen react specifically with the capsid protein and its intracellular precursor molecule. N-terminal sequence analysis of purified, mature capsid protein confirms this assignment and has identified the position at which precursor is cleaved.

Amino Acid Sequence↗

PubMed1992

Metabolic effects of dietary stearic acid in mice: changes in the fatty acid composition of triglycerides and phospholipids in various tissues.

The fatty acid patterns of triglycerides and phospholipids extracted from adipose tissue, liver, heart, kidney, spleen, and lung of 3 groups of C57BL/6 mice were determined after feeding diets rich in palmitic acid (16:0) (high palmitic: 16:0 = 45.1% of total fatty acids), stearic acid (18:0) (high stearic: 18:0 = 42.9% of total fatty acids) and oleic acid (18:1) (high oleic: 18:1 = 79.7% of total fatty acids) for 9 months. Triglyceride content of adipose, liver, heart, kidney, lung and spleen tissues was significantly enriched in palmitic acid in mice fed the high palmitic diet (range among all tissues: 19.9% +/- 0.2% to 29.0% +/- 1.9% of total fatty acids) and in oleic acid in mice fed the high oleic diet (range 56.0% +/- 1.9% to 71.6% +/- 1.2%). The stearic acid content of organ triglycerides in mice fed the high stearic diet ranged from 3.7% +/- 0.3% to 10.8% +/- 1.2%; however, the content of oleic acid on this diet (range: 57.0% +/- 1.8% to 71.4% +/- 1.7%) was similar to the one observed in mice fed the high oleic diet. In all organs, phospholipids had a significantly higher percentage of stearic acid (range: 23.5% +/- 0.9% to 51.5% +/- 6.6%) than triglycerides, regardless of diet. To evaluate the production of oleate from stearate and palmitate, 2 groups of mice were fed the high palmitic and the high stearic diets for 1 week and then injected intravenously with [1-14C]palmitate and [1-14C]stearate and the amount of labelled oleate in liver triglycerides was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

The complete nucleotide sequence of a feline calicivirus.

We have determined the complete sequence of a feline calicivirus. The virus genome is 7690 bases long and contains two large open reading frames. Proteins specified by these have similarity to those encoded in the corresponding regions of a candidate calicivirus rabbit hemorrhagic disease virus, but are distinctly different from those specified by another such virus, hepatitis E virus. A third, small open reading frame at the 3' end of the genome is present in both feline and rabbit viruses but is absent from hepatitis E. These findings suggest that the calicivirus family, which consists of a single genus, may require subdivision.

Amino Acid Sequence↗

PubMed1992

Uridine and cytidine nucleotide synthesis in renal hypertrophy: biochemical differences in response to the growth stimulus of diabetes and unilateral nephrectomy.

The effects of unilateral nephrectomy (UN) and streptozotocin (STZ) diabetes on the activities of enzymes involved in uridine and cytidine synthesis in early renal growth (3-14 days after stimulus to growth) have been compared. Measurements were also made of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) and of glucose 6-phosphate (G6P), UDP-glucose, and glycogen, in relation to phosphoribosyl pyrophosphate, ribonucleotide, and complex carbohydrate formation. There were striking differences in the activities of CTP synthetase, G6PDH, and 6PGDH in the two conditions, with a three-fold increase in all three enzymes at 3 and 5 days and a two-fold increase above basal values at 14 days of STZ diabetes. The UN group showed no significant change in CTP synthetase at any stage and the activity of G6PDH and 6PGDH only kept pace with renal growth. Changes in routes of uridine synthesis were less marked, with a more rapid rise in carbamoyl-phosphate synthetase (glutamine) and a lesser response of dihydroorotate dehydrogenase in the UN relative to the STZ-diabetic groups. The enzymes of complex II and of uracil phosphoribosyltransferase showed essentially similar patterns during renal hypertrophy in UN and STZ diabetes. The parallel increase in CTP synthetase, G6PDH, and 6PGDH in the kidney in diabetes, also known to increase in growth situations in hepatomas and in renal tumors, is discussed in relation to hormone signals involved in renal growth. The importance of the concentration of CTP, and thus of CTP synthetase, in the CTP-cytidyltransferase reaction, an enzyme with a high Km for CTP, makes the present observation of the striking increase in CTP synthetase in STZ diabetes of particular interest in relation to phosphatidylcholine formation and hormone signal transduction.

Animals↗

PubMed1992

Pyrimidine nucleotide synthesis in the rat mammary gland: changes in the lactation cycle and effects of diabetes.

Measurements have been made of the activities of the enzymes of the de novo and salvage pathways of pyrimidine synthesis (carbamoyl phosphate synthetase II (glutamine) (EC 6.3.5.5); dihydroorotate dehydrogenase (EC 1.3.99.11); the overall activity of Complex II (orotate phosphoribosyl pyrophosphate transferase (EC 2.4.2.10) and orotidine 5-phosphate decarboxylase (EC 4.1.1.23); uracil phosphoribosyltransferase (EC 2.4.2.9)) in the mammary gland of rats at different stages of the lactation cycle and the effects of diabetes on the activity of these enzymes in lactation have been studied. From a consideration of the changes in enzyme activities and the changes in the tissue concentration of phosphoribosyl pyrophosphate, an activator of the de novo pathway and substrate for both the de novo and salvage routes, it is concluded that the de novo pathway is the major route of pyrimidine synthesis in mammary tissue. Diabetes decreases the activity of the enzymes of the de novo pathway; the effects are particularly marked for Complex II. The present results on pyrimidine synthesis are compared to the pattern for purine synthesis previously published.

Animals↗

PubMed1992

Apramycin resistance plasmids in Escherichia coli: possible transfer to Salmonella typhimurium in calves.

An outbreak of salmonellosis in calves was monitored for persistence of Salmonella typhimurium excretion in faeces and the effect of treatment with apramycin. Prior to treatment apramycin-resistant Escherichia coli were present but all S. typhimurium isolates were sensitive. Following the treatment of six calves with apramycin, apramycin-resistant S. typhimurium were isolated from two treated calves and one untreated calf. Plasmid profiles of E. coli and S. typhimurium were compared and plasmids conferring resistance to apramycin and several other antibiotics were transferred by conjugation in vitro from calf E. coli and S. typhimurium isolates to E. coli K-12 and from E. coli to S. typhimurium. The plasmids conjugated with high frequency in vitro from E. coli to S. typhimurium, and hybridized to a DNA probe specific for the gene encoding aminoglycoside acetyltransferase 3-IV (AAC(3)-IV) which confers resistance to apramycin, gentamicin, netilmicin and tobramycin.

Animals↗

PubMed1992

Activation of B lymphocytes by NK cells.

The ability of NK cells to induce differentiation of B lymphocytes to IgM secretion in vitro has been investigated. Homogeneous preparations of NK cells obtained from IL-2 propagated splenocytes from SCID mice were found to have the ability to induce resting B lymphocytes to proliferate and secrete significant amounts of IgM. The induction is greatly enhanced by the presence of both IL-2 and IL-5 and does not require T lymphocytes or adherent cells in the responding population. Cell contact between the two populations is not necessary suggesting that the effect is mediated by soluble factor(s) which can be produced even by irradiated NK cells. Because the activity cannot be replaced by either r-tau-IFN or tumor necrosis factor-alpha or inhibited by antibodies to these lymphokines, a novel NK cell-derived factor(s) may be involved. The implications of this interaction between NK cells and B lymphocytes are discussed.

Animals↗

PubMed1992

Comparison of continuous versus intermittent furosemide administration in postoperative pediatric cardiac patients.

OBJECTIVE: To compare the effects of furosemide administered by intermittent iv infusion vs. continuous iv infusion on urine output, hemodynamic variables, and serum electrolyte concentrations. DESIGN: Prospective, randomized trial. SETTING: Pediatric ICU. PATIENTS: Postoperative pediatric cardiac patients. INTERVENTIONS: Patients were assigned to either the continuous iv infusion or the intermittent infusion groups. The intermittent group received 1 mg/kg iv of furosemide every 4 hrs to be increased by 0.25 mg/kg iv every 4 hrs to a maximum of 1.5 mg/kg iv if the urine output was less than 1 mL/kg.hr. The continuous infusion group received an initial furosemide dose of 0.1 mg/kg iv (minimum 1 mg) followed by an iv infusion rate of 0.1 mg/kg.hr of furosemide to be doubled every 2 hrs to a maximum of 0.4 mg/kg.hr if the urine output was less than 1 mL/kg.hr. MEASUREMENTS AND MAIN RESULTS: Demographic variables, fluids, electrolyte and inotropic requirements were the same in both groups. A significantly (p = .045) lower daily dose of furosemide (4.90 +/- 1.78 vs. 6.23 +/- 0.62 mg/kg.day) in the continuous iv infusion group produced the same 24-hr urine volume as that of the intermittent group. There was more variability in urine output in the intermittent group as well as more urinary losses of sodium (0.29 +/- 0.15 vs. 0.20 +/- 0.06 mmol/kg.day, p = .0007) and chloride (0.40 +/- 0.20 vs. 0.30 +/- 0.12 mmol/kg.day, p = .045). CONCLUSION: Furosemide administered by continuous iv infusion is advantageous in the post-operative pediatric patient because of a more controlled and predictable urine output with less drug requirement and less urinary loss in sodium and chloride.

Cardiac Surgical Procedures↗

PubMed1992

Demonstration of sites of latency of infectious laryngotracheitis virus using the polymerase chain reaction.

Mature laying chickens were inoculated intratracheally with a field strain of infectious laryngotracheitis (ILT) virus. Tracheal swabs were collected regularly from all birds for virus culture. At various times post-inoculation, pairs of birds were killed and tissues removed for detection of virus products using conventional tissue homogenization and culture, organ culture, indirect immunofluorescence (IF) and also the polymerase chain reaction (PCR). The latter was used to detect a DNA sequence from the ILT virus thymidine kinase gene. Following inoculation the birds developed mild respiratory disease with clinical signs characteristic of ILT from 3 to 10 days post-inoculation. Trachea and turbinate tissues were virus-positive as determined by virus isolation, organ culture, IF and PCR on day 4 post-inoculation. After recovery from the acute phase, virus shedding initially ceased, then intermittent, low level shedding was recorded for five of the six remaining birds. In an attempt to locate sites of latency, pairs of birds were sampled at 31, 46 and 61 days post-inoculation. Virus was not detected in upper respiratory tract or ocular tissues by conventional techniques, or in the trigeminal, proximal and distal ganglia. All tissues were also negative by PCR, except for the trigeminal ganglia of five of the six birds. All PCR-positive birds had previously shed ILT virus intermittently between days 19 and 59 post-inoculation. As we did not detect viral DNA in any of the other tissues sampled from clinically recovered birds, we conclude that the trigeminal ganglion is the main site of latency of ILT virus.

Animals↗

PubMed1992

Protein components specifically associated with prespliceosome and spliceosome complexes.

We have carried out a systematic analysis of the protein composition of highly purified mammalian spliceosomes. We show that > 30 distinct proteins, including 20 previously unidentified components [designated spliceosome-associated proteins (SAPs)], are specifically associated with the spliceosome in a salt-resistant complex. In contrast to these spliceosome-specific proteins, we show that hnRNP proteins are not tightly associated with purified prespliceosome and spliceosome complexes. The splicing factor U2AF65, U1 snRNP-specific proteins, and several SAPs are present in the earliest prespliceosome complex (E). A set of 10 proteins is then added to the first ATP-dependent prespliceosome complex (A), and concomitantly, a significant decrease in the level of U2AF65 is observed. The fully assembled spliceosome is formed by the addition of 12 proteins in a reaction that requires ATP and both the 5' and 3' splice sites.

Adenosine Triphosphate↗

PubMed1992

Differential binding of heterogeneous nuclear ribonucleoproteins to mRNA precursors prior to spliceosome assembly in vitro.

We have investigated the composition of the earliest detectable complex (H) assembled on pre-mRNA during the in vitro splicing reaction. We show that most of the proteins in this complex correspond to heterogeneous nuclear ribonucleoproteins (hnRNP), a set of abundant RNA-binding proteins that bind nascent RNA polymerase II transcripts in vivo. Thus, these studies establish a direct parallel between the initial events of RNA processing in vitro and in vivo. In contrast to previous studies, in which total hnRNP particles were isolated from mammalian nuclei, we determined the hnRNP composition of complexes assembled on individual RNAs of defined sequence. We found that a unique combination of hnRNP proteins is associated with each RNA. Thus, our data provide direct evidence for transcript-dependent assembly of pre-mRNA in hnRNP complexes. The observation that pre-mRNA is differentially bound by hnRNP proteins prior to spliceosome assembly suggests the possibility that RNA packaging could play a central role in the mechanism of splice site selection, as well as other posttranscriptional events.

Adenosine Triphosphate↗

PubMed1992

Murine natural killer cells and marrow graft rejection.

Rejection of bone marrow transplants in lethally irradiated mice differs from rejection of solid tissue grafts in several respects. The genetic laws that govern rejection of solid tissue grafts often fail with hemopoietic grafts. For example, F1 hybrids between two H-2 disparate strains of mice often reject parental bone marrow cells (BMC), and conversely, marrow cells of F1 hybrids (H-2 heterozygous) are usually not rejected by either parent or an unrelated allogeneic recipient. Thus, unlike the classical MHC antigens, the hemopoietic histocompatibility (Hh) antigens relevant in marrow graft rejection are inherited in a recessive pattern. The major Hh (Hh-1) locus maps within the mouse H-2 complex between the H-2S and H-2D regions, and it can therefore be dissociated from the class-I MHC genes. Nevertheless, it is possible that class-I MHC antigens play a role in the formation or expression of Hh-1 antigens. Three models that explain the possible relationship between class-I MHC and Hh-1 genes and the noncodominant pattern of inheritance of Hh antigens are presented. The effector cells responsible for resisting BMC grafts are different from those responsible for rejection of solid tissue grafts. Three cell types, natural killer cells (CD3-, NK1.1+), cytotoxic T cells (CD3+, CD8+), and T cells with natural killer cell markers (CD3+, NK1.1+) have been implicated in the rejection of BMC grafts. Involvement of these cell types is reviewed and the relative roles played by each are discussed. Evidence supporting the existence of Hh-1 specific subsets of NK cells is presented.

Animals↗

PubMed1992

Induction and enhancement of feline infectious peritonitis by canine coronavirus.

Preexisting antibody to feline infectious peritonitis virus (FIPV) causes acceleration and enhancement of disease on subsequent infection of cats with FIPV. Other workers have shown that canine coronavirus (CCV) can infect cats subclinically, but have found no evidence of enhancement of, or protection against, subsequent FIPV infection. With various isolates of CCV, we determined that 1 strain of CCV can induce transient mild diarrhea in cats and, furthermore, that previous infection with CCV causes acceleration and enhancement of subsequent infection with FIPV. In addition, sequential inoculation of cats with another strain of CCV caused lesions indistinguishable from those of FIP, without exposure at any time to FIPV.

Animals↗

PubMed1992

Hematologic relapse of chronic myelogenous leukemia following allogeneic bone marrow transplantation: apparent graft-versus-leukemia effect following abrupt discontinuation of immunosuppression.

Two patients with hematologic relapse of chronic myelogenous leukemia (CML) following allogeneic BMT were treated by abrupt discontinuation of cyclosporine. Both patients rapidly attained complete hematologic and cytogenetic remission and remain free of disease with long follow-up. In the first patient, disappearance of CML was associated with the development of graft-versus-host disease (GVHD). In the second patient GVHD did not develop until after clearing of disease had been documented by cytogenetic analysis. Laboratory studies in the second patient disclosed the presence of lytic activity against both K562 and autologous CML cells that enhanced with IL2. Correlation with serial immunophenotyping data from this patient suggests that the effector for this graft-versus-leukemia (GVL) reaction could have been a T lymphocyte. Abrupt discontinuation of post-transplant immunosuppression with cyclosporine may represent a therapeutic approach to CML which has recurred following BMT. Moreover, investigation of this clinical phenomenon in subsequent cases may permit direct study of the cellular mechanisms involved in the GVL effect.

Adult↗