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Biomedical subjects

R D Allen

Publications and source records attributed to R D Allen.

At least 127 records · Page 7Linked to original sources
PubMed1989

Percutaneous fine needle aspiration biopsy of canine pancreas allograft provides diagnosis of treatable rejection.

Despite improved pancreas transplant graft survival, early diagnosis of rejection remains a clinical challenge. Using a canine model of whole pancreas transplantation with bladder exocrine drainage we have shown fine needle aspiration biopsy (FNAB) to provide an earlier diagnosis of rejection than fall in urinary amylase (UA). The aim of this study was to assess the ability of anti-rejection therapy to reverse rejection when the diagnosis was based on either FNAB findings or a fall of UA. Sixteen dogs received a total pancreas allograft with an inadequate dose of oral cyclosporine (5 mg/kg/day). Fasting UA levels were measured daily and percutaneous FNAB with ultrasound guidance was performed three times weekly on all dogs. The diagnosis of rejection was made in alternate dogs with either a fall of UA to a level of less than 5000 IU/liter (median 7 days) or when the total corrected increment (TCI) of aspirated infiltrating cells was greater than 2.6 (median 5 days). Anti-rejection therapy consisted of methylprednisolone 10 mg/kg/day iv for 5 days and an increase of oral cyclosporine dosage to 25 mg/kg/day. Early vascular thrombosis (Day 2) occurred in three allografts. Diagnosis of rejection based on a low level of UA permitted the successful reversal of rejection in only one of six grafts, whereas five of seven grafts were successfully treated when rejection diagnosis was based on FNAB. Median allograft survivals were 9 days (range 8-19) and 32 days (range 11-63), respectively (P less than 0.01). The earlier diagnosis of allograft rejection made by FNAB improved the ability of conventional anti-rejection therapy to reverse pancreas allograft rejection and significantly improved allograft survival.

Amylases↗
PubMed1989

Murine "viable motheaten" mutation reveals a gene critical to the development of both B and T lymphocytes.

In lethally irradiated normal mice reconstituted with both normal and autoimmune mutant viable motheaten (mev) bone marrow, the mev-derived B and T cells display aberrant behavior, while those derived from the normal bone marrow develop and function normally. The observed developmental abnormalities of mev B and T lymphocytes are therefore intrinsic to these cell types, rather than being determined by defective influences from the cells' environment. These data bring into question the in vivo significance of reported intercellular regulatory defects in motheaten (me) and mev mice and suggest that these mutations affect a gene whose product acts cell autonomously in the development of several hematopoietic cell lineages including B and T lymphocytes.

Animals↗
PubMed1989

An investigation of mitochondrial inner membranes by rapid-freeze deep-etch techniques.

Physical fixation by rapid freezing followed by freeze-fracture and deep-etching has provided the means for potentially seeing the three-dimensional arrangement in the native state of particles on mitochondrial inner membranes. We have used these techniques to study the tubular cristae of Paramecium in the hope of determining the arrangement of F1 complexes, their abundance, and location in the membranes. We also sought information regarding other respiratory complexes in these membranes. Our results, supported by stereo pairs, show that F1 complexes are arranged as a double row of particles spaced at 12 nm along each row as a zipper following the full length of the outer curve of the helically shaped tubular cristae. There are an average of 1,500 highly ordered F1 complexes per micrometer squared of 50-nm tubular cristae surface. The F1 complexes definitely lie outside the membranes in their native state. Other particle subsets, also nonrandomly arrayed, were seen. One such population located along the inner helical curve consisted of large 13-nm-wide particles that were spaced at 30 nm center-to-center. Such particles, because of their large size and relative abundance when compared to F1 units, resemble complex I of the respiratory complexes. Any models attempting to understand the coupling of respiratory complexes with F0F1 ATPase in Paramecium must take into account a relatively high degree of order and potential immobility of at least some of these integral membrane complexes.

Animals↗
PubMed1989

Nuclear factors interact with a soybean beta-conglycinin enhancer.

Upstream sequences of the gene encoding the alpha' subunit of beta-conglycinin were analyzed for interactions with nuclear proteins from immature soybean seeds. Two factors were identified that interact with specific sequence elements within 257 base pairs 5' of the transcription start site. One factor, SEF 3, binds exclusively to a region composed of two elements located at -183 to -169 base pairs and -153 to -134 base pairs relative to the start of transcription. Each of these sites includes the hexanucleotide sequence AACCCA, which may serve as a primary recognition sequence. During seed development, SEF 3 binding activity was found to increase in soybean embryos during the time of beta-conglycinin synthesis and to decrease as seeds neared maturity. The position of the SEF 3 binding sequence corresponds with a previously reported seed-specific enhancer region, and it seems likely that this factor may act as a positive regulator of transcription of the beta-conglycinin, alpha' subunit gene in developing soybean seeds. The second factor, SEF 4, also binds within the -257 to -77 region but also interacts with sites located further upstream.

Antigens, Plant↗
PubMed1989

Intracellular binding of wheat germ agglutinin by Golgi complexes, phagosomes, and lysosomes of Paramecium multimicronucleatum.

The compartments of the Paramecium digestive system were investigated with wheat germ agglutinin (WGA). By use of cryosectioning or Lowicryl K4M embedding combined with pulse-chase studies and WGA-gold labeling, WGA binding sites were located on membranes of the phagosome-lysosome system, including all four stages of digestive vacuoles, the discoidal vesicles, acidosomes, and lysosomes. In addition, the contents of lysosomes, cisternae at the trans face of Golgi stacks, and coated and uncoated blebs and vesicles at the putative trans Golgi network bind to WGA. Crystal-containing vacuoles characteristic of mid-log to stationary-phase cultures are enclosed by heavily labeled membranes. Alveoli underlying the plasma membrane sometimes contain binding sites, particularly on their outer membranes. Ciliary membranes previously shown to be labeled with WGA-FITC are negative in frozen thin and Lowicryl K4M sections. The presence of WGA binding sites on the trans face of the Golgi stack is the first indication in ciliated protozoa, such as Paramecium, of probable Golgi complex involvement in glycosylation similar to that in higher organisms. WGA-labeled coated vesicles in the endoplasm apparently lose their coats and coalesce to form lysosomes. Our study shows that WGA can be used as a specific intracellular marker of all digestive system membranes and of lysosomal content. These results support and extend our published scheme of membrane flow and recycling in Paramecium by providing another means of demonstrating membrane relationships.

Animals↗
PubMed1989

Improvement of canine pancreas-allograft survival with diagnosis of rejection by fine-needle aspiration biopsy.

Early diagnosis of rejection in pancreas-allograft transplantation remains a clinical challenge. The aim of this study was to assess the ability of antirejection therapy to reverse rejection when the diagnosis was based on either fine-needle aspiration biopsy (FNAB) or urinary amylase (UA). Sixteen dogs received a total-pancreas allograft with exocrine drainage into the bladder. Initially, a deliberately low dose of cyclosporin was given. Monitoring included percutaneous FNAB with ultrasound guidance and fasting spot measurements of UA. The diagnosis of rejection was made in alternate dogs when UA fell to less than 5000 IU/L (group A) or when the total corrected increment (TCI) of aspirated infiltrating cells was greater than 2.6 (group B). Antirejection therapy consisted of 10 mg.kg-1.day-1 i.v. methylprednisolone for 5 days and an increased dose of cyclosporin (25 mg.kg-1.day-1). The median allograft survival was 9 days (range 8-19) in group A and 32 days (range 10-63) in group B (P = .01). A fall in UA permitted the successful reversal of rejection in only one of six grafts, whereas five of seven grafts were successfully treated when rejection diagnosis was based on FNAB. In conclusion, early diagnosis of rejection was achieved by FNAB, improving the ability of antirejection therapy to reverse pancreas-allograft rejection and prolong survival.

Animals↗
PubMed1988

Organization of the sunflower 11S storage protein gene family.

We have isolated and characterized genes encoding the sunflower 11S globulin seed storage proteins, collectively termed helianthinin. One gene, designated HaG3, has a primary transcription unit of about 1750 nucleotides including two short intervening sequences. The predicted precursor polypeptide from HaG3 is 493 amino acids long, is rich in glutamine and other nitrogen-rich amino acids and includes the amino acid sequence NGVEETICS. This sequence is highly conserved among 11S seed storage proteins and is involved in the proteolytic processing of these polypeptides. Additional helianthinin sequences are conserved among other seed storage protein genes. Analysis of various cDNA and genomic sequences indicates helianthinins are encoded by a small gene family that includes a minimum of two divergent subfamilies.

2S Albumins, Plant↗
PubMed1988

Triple therapy in cadaver renal transplantation.

One hundred consecutive first (n = 72) and regrafted (n = 28) cadaver renal allograft recipients were immunosuppressed with cyclosporin, azathioprine and prednisolone (triple therapy) and followed for a median of 17.3 months (range, 7-26 months). Actuarial patient survival at 12 and 24 months was 97.7 per cent. Actuarial graft survival at 12 and 24 months was 79.5 per cent (first graft recipients 81.3 per cent and regrafted recipients 75 per cent). HLA-DR matching significantly improved graft survival which was 93 per cent at 1 year in patients given HLA-DR compatible kidneys, compared with 83 and 54 per cent, respectively, in patients who received kidneys mismatched for one or two HLA-DR antigens. There were 0.8 (s.d. = 0.7) episodes of acute rejection per patient during the first 3 months after transplantation. Triple therapy provides effective immunosuppression without evidence of over immunosuppression and reduces the incidence of cyclosporin side-effects. Although acute nephrotoxicity was uncommon, serum creatinine remained elevated 6 and 12 months after transplantation.

Adolescent↗
PubMed1988

Dynamic organization of Physarum plasmodium.

Birefringent fibrils (BRFs) with a positive sign composed of bundles of F-actin were found throughout the Physarum plasmodium with the mode of existence differing regionally. In the zone behind the leading edge of an advancing plasmodium, where cytoplasmic sol and gel were still not well differentiated, more BRFs came to the foreground when the endoplasm flowed backward (emptying phase), and a substantial portion disappeared when the endoplasm flowed forward (filling phase), except for nodes, from which BRFs were reorganized in the early emptying phase of each cycle. BRFs found in the wall of the streaming channel in the posterior network and the branched vein section ran in parallel to or helically around the channel. They were much more stable and maintained strong birefringence irrespective of the direction of the cytoplasmic flow. When the fan-like expanse ceased moving forward, the BRFs no longer appeared and disappeared cyclically but persisted in the area which had previously been the front. We concluded that the site of the active contraction-relaxation rhythm in an advancing plasmodium with antero-posterior polarity is restricted to its frontal zone and that the rest of the plasmodium is in a state of "tonus" which continuously imparts a certain level of hydrostatic pressure to the interior. The meaning of the tonus and the mechanics of tensile force production in the plasmodium are discussed in terms of a working hypothesis arrived at from the phase relationship between isometric and isotonic contraction waves.

Birefringence↗
PubMed1988

Specific binding proteins for selenium in rat tissues.

The preventive and therapeutic potential of selenium (Se), a micronutrient, against cancer has been well documented in several test systems, but the mechanism of its action is not known. The possibility that Se might function in a manner similar to steroid hormones and retinoids through mediation of cellular receptors was examined. A specific 2S cellular binding protein (SeBP) for Na2[75Se]O3 was detected in rat tissue extracts. Liver and intestine exhibited highest levels of SeBP, and heart, uterus and spleen had the lowest levels. Oral administration of Na2[75Se]O3 to rats resulted in its uptake by the tissues with concomitant appearance of [75Se]SeBP complex. The protein binds sodium selenite with moderately high affinity; the apparent dissociation constant was determined by Scatchard analysis to be 1.1 X 10(-7) M. SeBP focused at pH 5.3 upon isoelectric focusing in ampholines of pH 3-10. Competitive binding affinity studies with unlabeled test compounds revealed that selenium dioxide and selenocystine showed high binding affinity (90-95%) for the selenite-binding site on SeBP. Sodium selenate, elemental Se powder, and selenomethionine, however, showed poor competition with sodium selenite. Biological activity of the above selenocompounds, as expressed by others, correlate with their binding affinities for SeBP. Sodium sulfite showed 35% inhibition of Na2[75Se]O3 binding, but sulfate showed none. Two ultimate carcinogens, N-methyl-N-nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine, and two retinoids, retinol and retinoic acid, showed less than 10% inhibition of binding. Interaction of Se with SeBP is completely blocked by thiol inhibitors. Plasma transport of Na2[75Se]O3 is mediated by a protein with a mol. wt of 68,000, which is presently identified, by immunoprecipitation studies as well as by Affi-Gel Blue column chromatographic experiments, as serum albumin. The results suggest that the plasma transport of Se is facilitated by albumin, and that the intracellular transport of Se for its biological functions is accomplished by SeBP.

Animals↗
PubMed1988

Early diagnosis of rejection of canine pancreas allografts by fine-needle aspiration biopsy.

In pancreatic allograft transplantation with bladder exocrine drainage, falls in urinary amylase (UA) levels have been shown to be an earlier marker of rejection than rises in fasting blood glucose levels. Nevertheless, this is often too late for reversal of the rejection process. In an attempt to diagnose rejection earlier, fine-needle aspiration biopsy was correlated with UA and graft histology. Sixteen dogs were given total pancreatic allografts, 10 without immunosuppression and 6 with triple therapy. FNAB and needle-core biopsies were performed on days 0, 2, 4, 7, 9, 24, and 30 and/or at functional rejection, defined as a fasting UA level of less than 5000 IU/L. Cytocentrifuge preparations of the FNABs were evaluated by total corrected increment (TCI) scores. These increased significantly from 1.0 (+/- 0.4; mean +/- SEM) 6 days, to 3.0 (+/- 1.2) 4 days before functional rejection. The increase was due to the presence of blast cells and macrophages. The TCI of healthy immunosuppressed grafts remained below 1.6 for 30 days after transplantation and was greater than 5.0 when pancreatitis or acute rejection was seen on conventional histology. Minimal histologic change had significantly lower TCI scores than both acute rejection (P less than 0.01) and pancreatitis (P less than 0.001). Acute rejection and pancreatitis were distinguished by a significant difference in increments of monocytes/lymphocytes and macrophages. In contrast to FNAB, UA levels did not differentiate minimal change from acute rejection but were a reliable marker of end-stage rejection.

Amylases↗
PubMed1988

Regulation of isocitrate lyase gene expression in sunflower.

A cDNA sequence that encodes a portion of sunflower (Helianthus annuus L.) seedling isocitrate lyase was selected from a lambda gt11 cDNA library derived from sunflower seedling cotyledon poly(A)(+) messenger RNA. The library was screened for bacteriophage recombinants that expressed antigens which reacted with antisera directed against cotton seed isocitrate lyase. The isolated cDNA hybridized with a 2 kilobase RNA species that was first detectable in maturing sunflower embryos 19 days after flowering and remained at a constant low level through seed desiccation. The prevalence of this transcript in sunflower cotyledons increased by about 10-fold within 2 days after inhibition in darkness, and transcript levels began to decrease by 5 days after imbibtion. During the first 2 days of germination and growth of sunflower seedlings in light, the rate of isocitrate lyase mRNA accumulation was greater than the rate observed during this period in dark-grown seedlings, giving peak levels about 2-fold higher than corresponding levels in dark-grown seedlings. Illumination of seedlings also promoted an earlier, and more rapid decline of isocitrate lyase transcripts. Peak levels of isocitrate lyase mRNA preceded a corresponding peak in immunologically detectable isocitrate lyase polypeptides by about 24 hours. Isocitrate lyase expression in sunflower cotyledons is developmentally regulated and is modulated, in seedlings, by exposure to light. Mechanisms that control these processes appear to function primarily at the level of mRNA accumulation and are likely to involve changes in transcription rates and/or mRNA stability.

Journal Article↗
PubMed1988

Monitoring of canine pancreas allograft function with measurements of urinary amylase.

A canine model of whole pancreas transplantation with pancreaticocystostomy was studied for predictability of graft rejection using urinary amylase (UA) monitoring. Six pancreatectomized dogs were transplanted without immunosuppression and with acute rejection occurring at a median of 9.5 days (range 7-12 days). A differential loss of allograft exocrine and endocrine function was demonstrated, with a gradual decrease in UA after transplantation but maintenance of fasting blood glucose levels (FBGL) till the day before complete loss of graft structure. Another 13 dogs treated with cyclosporin (25 mg/kg per day) had prolonged graft survival (P less than 0.01) with an actuarial median survival of 91 days (range 8-159 days). Five allografts were lost because of rejection and eight dogs died with functioning grafts. Fasting spot levels of UA less than 5000 iu/l or less than 10,000 iu/l had a positive predictivity of graft failure of 71% or 31%, respectively. Falls of UA levels of greater than 75% in 24 h and 48 h were seen equally in both rejecting and functioning allografts. This study confirmed the role of UA as an earlier marker of rejection than FBGL. The clinical role of UA will be important, but its use as a predictor of pancreas rejection may be dependent on a fall to a predetermined level rather than the rate of fall.

Amylases↗
PubMed1988

A survey of lectin binding in Paramecium.

To better understand the general distribution of glycoproteins and the distribution of specific glycoprotein-bound sugar residues in Paramecium, a survey of the binding pattern of selected lectins was carried out in P. tetraurelia, P. caudatum, and P. multimicronucleatum. Lectins studied were concanavalin A (Con A), Griffonia simplicifolia agglutinins I and II (GS I and GS II), wheat germ agglutinin (WGA), Ulex europaeus (UEA I), peanut agglutinin (PNA), Ricinis communis toxin (RCA60) and agglutinin (RCA120), soybean agglutinin (SBA), Bauhinia purpurea agglutinin (BPA), Dolichos biflorus agglutinin (DBA), and Maclura pomifera agglutinin (MPA). Those giving the most distinctive patterns were Con A, GS II, WGA, UEA I, and PNA. No significant differences were found between the three species. Concanavalin A, a mannose/glucose-binding lectin, diffusely labeled the cell surface and cytoplasm and, unexpectedly, the nuclear envelopes. Events of nuclear division, and nuclear size and number were thus revealed. Both WGA and GS II, which are N-acetylglucosamine-binding lectins, labeled trichocyst tips, the cell surface, and the oral region, revealing stages of stomatogenesis. The lectin WGA, in addition, labeled the compartments of the phagosome-lysosome system. The lectin PNA, an N-acetyl galactosamine/galactose-binding protein, was very specific for digestive vacuoles. Finally, UEA I, a fucose-binding lectin, brightly labeled trichocysts, both their tips and body outlines. We conclude that a judicious choice of lectins can be used to localize glycoproteins and specific sugar residues as well as to study certain events of nuclear division, cellular morphogenesis, trichocyst discharge, and events in the digestive cycle of Paramecium.

Animals↗