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Biomedical subjects

R D Allen

Publications and source records attributed to R D Allen.

At least 145 records · Page 8Linked to original sources
PubMed1988

Phagosome formation in Paramecium: effects of solid particles.

Digestive vacuole (DV) formation in Paramecium can be separated into four steps: sequestration and recycling of the spent DV membrane, sweeping and concentrating of particles into the nascent DV, vacuole growth, and the release of the nascent DV. How the size, load and surface charge of solid particles affected formation and subsequently the digestive processes in log-phase cells were investigated. Pulsing cells continuously with beads resulted in an initial linear increase, followed by a steady state, of labelled DVs. Above a certain threshold concentration, the rate of formation and the size of the DVs formed (as well as the steady state) all increased with increasing bead load, so that for a 16-fold increase in bead load, a corresponding fourfold increase in the incorporation of the recycled membrane into the DVs was observed. The threshold values, which depended on the sensitivity of the technique used to score these DVs, were lowered as bead size increased. The steady state of labelled DVs was shown to correspond to a strict balance between the formation and defecation rates as shown by efflux measurements and pulse-chase protocols using two consecutive labels. The duration of the pulse required to reach these steady states was inversely proportional to the logarithm of the bead number at low bead loads but remained constant at higher bead loads. The formation rates and the DV size were similar when cells were pulsed with beads from 0.5 to 3 microns, but DV size increased using beads of 4.5 and 5.7 microns. The maximal bead size that could be ingested was approximately 10 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Characterization of monoclonal antibodies to trichocyst antigens in Paramecium.

Ten mouse monoclonal antibodies (mAbs) were raised against trichocyst contaminants present in crude or enriched lysosome fractions of Paramecium multimicronucleatum. Using an indirect immunofluorescence assay (IFA) and immunogold labelling on frozen thin sections, epitopes were located on the outer edge, cortex and the core of the trichocyst body, as well as the sheath covering the tip. Except for the two on the tip, epitopes were reactive after SDS-PAGE under non-reducing conditions. Four mAbs (131C1E8, A1-3, A16-2, D7) were directed to a trio of bands of 37, 34 and 29 (x 10(3] Mr from the beaded or meshlike trichocyst body sheath. A fifth mAb (135B9E7), directed to epitopes on the cortex inside the beaded body sheath, reacted strongly with the 37 and 34 bands, but weakly with the 29 x 10(3) Mr band. The last three mAbs (270D5, 22D7F2, D8) were reactive with one or more of three families of antigens found on the trichocyst core. mAb 270D5 reacted mainly with the 34 and 29 (x 10(3] Mr bands of the family containing the above trio, while mAb 22C7F2 reacted consistently with the 47 x 10(3) band of the higher Mr family but variably with both the trio of bands and the 17 x 10(3) band of the lower Mr family. mAb D8, which was directed to epitopes on the trichocyst core and small vesicles in the endoplasm, reacted only with the 29 x 10(3) Mr band. The mAbs were cross-reactive with the trichocysts of P. primaurelia, P. tetraurelia, P. caudatum and P. calkinsi with some small variation in blotting patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Birth weight prediction from remote ultrasound examination.

From 259 cases studied, 245 were selected in which a live-born infant was delivered within 35 days of a complete fetal ultrasound evaluation. Multiple linear regression using the least-squares method enable us to generate an equation that incorporated lapse time (examination-to-birth interval) with the natural logarithm of head circumference, femur length, and abdominal circumference to estimate birth weight. With a lapse time mean of 16 +/- 11 days and a range of zero to 35 days, the generated equation accurately predicted birth weight (R2 = 0.84; P less than or equal to .0001). For all birth weights, the mean error was -15 +/- 306 g, the percent mean error was 0.51 +/- 10.2%, and the mean absolute error of the estimate was 82 g/kg birth weight. This accuracy was maintained across the full range of lapse time observed. For examinations performed within one week of delivery (N = 71), this formula more accurately predicted birth weight than five existing static formulas tested. The accuracy observed during model development was confirmed during testing upon 167 non-model cases. The accurate prediction of birth weight from remote ultrasound data is possible when lapse time is included in the predicting equation. The clinical value of this model is suggested when ultrasound is unavailable or unreliable.

Birth Weight↗
PubMed1987

Interference of retinoic acid binding to its binding protein by omega-6 fatty acids.

Cellular retinoic acid-binding protein (CRABP) is the putative mediator of the biological effects of retinoic acid in the control of epithelial differentiation and tumorigenesis. Omega-6 fatty acids such as linoleic acid and arachidonic acid, precursors of prostaglandin synthesis, caused inhibition of retinoic acid binding to CRABP. These fatty acids, however, possessed lower affinity than retinoic acid for the binding protein. Omega-3 fatty acids, such as eicosapentaenoic acid and docosohexaenoic acid, did not cause such inhibition in the binding of retinoic acid. Whereas retinoic acid was a potent modulator of differentiation of F9 embryonal carcinoma cells, neither omega-3 nor omega-6 fatty acids showed any significant differentiation potential. Competition by omega-6 fatty acids with retinoic acid for CRABP may neutralize the binding protein-mediated biological functions of retinoic acid, and could thereby enhance tumor production.

Animals↗
PubMed1987

Cyclosporin conversion versus conventional immunosuppression: long-term follow-up and histological evaluation.

129 patients who received a cadaver renal transplant entered a randomised prospective trial of cyclosporin for 3 months with conversion to azathioprine and prednisolone compared with conventional therapy of azathioprine and prednisolone. In the 64 patients who received cyclosporin, actuarial patient survival was 92%, and actuarial graft survival was 72% and 67% at 1 and 4 years after transplantation. Graft survival was significantly better (p less than 0.03) than in the 65 patients who received conventional therapy, in whom actuarial patient survival was 94%, and actuarial graft survival was 59% and 47% at 1 and 4 years. Renal function and other side-effects improved quickly after conversion with the better renal function maintained throughout follow-up. Renal biopsies at 90 days and 1 year in all patients did not show consistent improvement after conversion from cyclosporin in the histological features that might be attributable to cyclosporin toxicity. After conversion, 32% of the patients had acute rejection, generally within 30 days. 1 graft was lost to early acute rejection after conversion and another was lost 3 months later from acute-on-chronic rejection. A total of 8 grafts were lost to chronic rejection in the cyclosporin-treated group and 6 in the conventional group. The improvement in renal function obtained with this protocol of short-term cyclosporin with conversion to azathioprine and prednisolone has to be balanced against the risk of acute rejection and even loss of the graft after conversion.

Administration, Oral↗
PubMed1987

Substructure of sidearms on squid axoplasmic vesicles and microtubules visualized by negative contrast electron microscopy.

We present a high-resolution electron microscopic study of the sidearms on microtubules and vesicles that are suggested to form the crossbridges which produce the microtubule-based vesicle transport in squid axoplasm. The sidearms were found attached to the surfaces of the anterogradely transported vesicles in the presence of ATP. These sidearms were made of one to three filaments of uniform diameter. Each filament measured 5-6 nm in width and 30-35 nm in length. The filaments in some of the sidearms had splayed apart by pivoting at their base, thereby assuming a "V" shape. The spread configuration illustrated the independence of the individual filaments. The filaments in other sidearms were closely spaced and oriented parallel to each other, a pattern called the compact configuration. In axoplasmic buffer containing AMP-PNP, structures indistinguishable from the filaments of the sidearms on the vesicles were observed attached to microtubules. Pairs of filaments, thought to represent the basic functional unit, were observed attached to adjacent protofilaments of the microtubules by their distal tips. These data support a model of vesicle movement in which a pair of filaments within a sidearm forms two crossbridges and moves a vesicle by "walking" along the protofilaments of the microtubule.

Adenylyl Imidodiphosphate↗
PubMed1987

Sequence and expression of a gene encoding an albumin storage protein in sunflower.

The complete sequence of a sunflower (Helianthus annuus) gene, HaG5, encoding a 2 S albumin storage protein was determined. The predicted unprocessed precursor has 295 amino acids, is rich in glutamine residues (24%) and contains a hydrophobic amino-terminus that is similar to the consensus signal peptide. Amino acid sequencing of the mature protein revealed extensive post-translational processing. Nuclease protection and primer extension analysis indicated a major transcriptional start 30 nucleotides 5' of the predicted ATG start codon. Additional sequence data, determined from a nearly full length cDNA recombinant, indicate that HaG5 is a member of a small gene family comprised of at least two divergent genes. Comparison of the predicted HaG5 gene product with sequences of other known plant proteins revealed distant but significant homology with the napins of Brassica and other heterogeneous seed proteins in the albumin superfamily.

2S Albumins, Plant↗
PubMed1987

Role of spermine in the cytotoxic effects of seminal plasma.

This report further characterizes the cytotoxic properties of seminal plasma and provides evidence for a role of spermine oxidation in the generation of seminal plasma cytotoxicity. Addition of spermine to lymphocyte cultures was found to result in a cytotoxic effect similar to that observed upon addition of seminal plasma. Furthermore, although seminal plasma is not cytotoxic in serum-free medium, addition of monoamine oxidase was sufficient to result in the generation of seminal plasma-associated cytotoxicity. Analysis of 73 individual seminal plasma samples indicated that all were cytotoxic, suggesting that this is an intrinsic property of seminal plasma. These results support a mechanism for seminal plasma cytotoxicity in which oxidation of spermine in seminal plasma by the amine oxidase of fetal calf serum results in generation of a cytotoxic product. It is hypothesized that this product plays a significant role in the phenomenon of seminal plasma immunosuppression. The general application of this principle to other fluids and tissues is discussed.

Animals↗
PubMed1987

Deep venous thrombosis after renal transplantation.

Four hundred and eighty consecutive renal transplant operations performed upon adults over a ten year period were reviewed to obtain the incidence of deep venous thrombosis (DVT) or pulmonary embolism (PE), or both. Using strict objective diagnostic criteria, 40 (8.3 per cent) thrombotic events were diagnosed, comprising 25 lower limb DVT alone, 11 DVT with PE and four PE alone. Four deaths were directly attributable to PE which was the fourth major cause of death in the review period. DVT was more common on the side of the transplant but the difference was not significant. The low incidence of thrombotic events (1.7 per cent) in the first month of transplantation does not suggest that chemical prophylaxis should be used during this period. However, the peak incidence occurred in the fourth month after transplantation which may be associated with a significant rise in mean hemoglobin concentration in both the thrombotic population and a control group of transplant recipients. Patient age at the time of transplantation and predisposing events, such as prolonged bedrest, further surgical treatment and pelvic pathology, were significant risk factors. All of the patients in the thrombotic population were receiving steroids at the time of diagnosis and no thrombotic events were demonstrated in patients receiving cyclosporin alone. The results of this review suggest that chemical prophylaxis is indicated for patients more than 40 years of age, with stable renal function and receiving steroids, who undergo periods of prolonged bedrest or further surgical treatment at some time after renal transplantation.

Adolescent↗
PubMed1987

Renal transplant nephrectomy.

There is surprisingly little about the problems of transplant nephrectomy reported in the literature, despite the frequency of the procedure and the recognition that it can be a difficult technical challenge. Of 480 kidneys transplanted during a ten year period, 154 (32 per cent) were later removed. One hundred and eleven (72 per cent) nephrectomies were performed because of uncontrollable acute rejection within three months of transplantation. Thirty-eight (25 per cent) nephrectomies were performed because of graft failure due to chronic rejection and five (3 per cent) were carried out for other reasons. The only significant problem that occurred during graft nephrectomy was difficulty in controlling bleeding which occurred at nine (6 per cent) operations. No patient died during the operation. In the postoperative period, there were two (1 per cent) complications, perforated peptic ulcer and pseudomembranous colitis, which led to death and 22 (14 per cent) which were successfully treated. These consisted of nine infections, five lymph leaks, four hematemeses, three secondary hemorrhages and one urine leak. No significant difference could be shown in morbidity and mortality with respect to the time lapse between transplantation and graft nephrectomy. Transplant nephrectomy need not be as hazardous a procedure as has often been recorded provided it is not performed by an inexperienced surgeon, although the decision as to when to abandon a graft is often a finely balanced one.

Graft Rejection↗
PubMed1987

Phagosomal acidification in Paramecium: effects on lysosomal fusion.

Phagosomes of paramecia and amoeba and endosomes of fibroblasts and other mammalian cells are acidified prior to lysosomal fusion. The question, whether the phagosomal acidification process in paramecia is required for phagosome-lysosome fusion, was studied using ionophores, weak bases, and cytochalasin B (CB) in combination with monoclonal antibodies, acid phosphatase (AcPase) cytochemistry, and lysosome morphometry. Digestive vacuoles (DVs) of known ages were treated and examined. In untreated cells, lysosome binding to the membrane of the acidified DV increased linearly with age and reached a maximum before lysosome-DV fusion. When the fusion of the acidosomes with the very young DVs was prevented by CB, causing a block in the normal vacuole-pH drop, lysosome binding to the DVs as well as the rate and extent of lysosome-DV fusion were all greatly reduced. These effects of CB were reversible. When present prior to acidification, three ionophores and two weak bases did not inhibit the acidosome-DV fusion but raised the phagosomal pH and reduced both the rates of DV acidification and of lysosome-DV fusion. However, when added after acidification but prior to lysosome-DV fusion, five of the six perturbants studied did not inhibit this fusion but prolonged the period when DVs remained AcPase positive. Lastly, lysosome-DV fusion rates were found to be related to acidification rates. We conclude that an inhibition in acidosome-DV fusion or a reduction in both the acidification rate and vacuolar-pH drop would inhibit lysosome-DV fusion.

Acid Phosphatase↗
PubMed1986

Fast axonal transport by neurons from the jellyfish Cyanea capillata.

Neurons of the motor nerve net of Cyanea capillata were examined using video-enhanced DIC optics. A variety of organelles were visible within the axons and many were mobile. To quantify the movement organelles were divided into three classes (large, medium, and small) and the rates, direction, and types of movement displayed by the different particle types examined. The overall behavior and rates of movement of transported particles were comparable with those in axons from other species. The largest particles, mainly mitochondria were the slowest moving but were the only particles to reverse their direction of movement or to undergo interactions with other particles. The fastest movement was by the small particles, but both they and medium sized particles were transported continuously. In addition, the linear elements in these axons underwent considerable lateral movement.

Animals↗
PubMed1986

ATP-dependent formation and motility of aster-like structures with isolated calf brain microtubule proteins.

Microtubule proteins isolated from calf brain will undergo gelation-contraction in the presence of ATP. We have now examined this process by video-enhanced contrast microscopy. After ATP addition to steady-state microtubules, slow (1-5 micron/min), linear movements of particles and microtubules toward aggregation centers occur. The resulting structures resemble mitotic spindle asters. During the time when gel contraction occurs, asters move (at 1-5 micron/min) toward other nearby asters. This is accompanied by the apparent shortening of the microtubules running between the asters. This is the first example of isolated microtubules undergoing a process that has similarities to half-spindle shortening during anaphase A. Formation of aster-like structures without preformed microtubule organizing centers raises the possibility that a similar process may contribute to microtubule organization in vivo.

Adenosine Triphosphate↗