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Biomedical subjects

R Mayer

Publications and source records attributed to R Mayer.

At least 163 records · Page 9Linked to original sources
PubMed1990

IL 3 and IL 6 do not induce bone resorption in vitro.

Bone resorption in vitro and in vivo can be induced by interleukin 1 (IL 1) and tumor necrosis factor (TNF), both of which are potent inflammatory cytokines. Additionally, there are other factors produced by cells which can active osteoclasts. Because diverse factors are involved in bone resorption, we examined the role of two other inflammatory cytokines, IL 3 and IL 6. IL 3 has been shown to induce the formation of osteoclast-like cells from precursors, while IL 6 is a potent mediator of inflammatory responses. Osteoclast activity in neonatal mouse calvaria was measured as 45Ca released into the supernatant fluid following a 48 hr incubation period with cytokine. Our results show that while parathyroid hormone (PTH) and IL 1 are potent inducers of bone resorption, neither IL 3 nor IL 6 displayed such activity.

Animals↗
PubMed1990

Pressure threshold for shock wave induced renal hemorrhage.

Studies were performed with an interest in determining a pressure threshold for extracorporeal shock wave induced renal damage. Histological evidence of intraparenchymal hemorrhage was used as an indicator of tissue trauma. Depilated C3H mice were anesthetized and placed on a special frame to enhance visualization and treatment of the kidneys in situ. A Wolf electrohydraulic generator and 9 French probe designed for endoscopic use were utilized to expose the kidneys to 10 double spherically divergent shock waves. Measurements of the shock waves revealed two positive pressure peaks of similar magnitude for each spark discharge. The kidneys were exposed to different peak pressures by choice of distance from the spark source and were removed immediately after treatment for histologic processing. A dose response was noted with severe corticomedullary damage apparent following 15 to 20 MPa shocks. Hemorrhage was more apparent in the medulla where evidence of damage could be seen following pressures as low as three to five MPa. When a latex membrane was interposed to prevent possible collapse of the initial bubble from the spark source against the skin surface, histological evaluation revealed substantial reduction of severe tissue damage associated with the highest pressures tested, 20 MPa. However, the threshold level for evidence of hemorrhage remained about three to five MPa. Hydrophonic measurements indicated that the membrane allowed transmission of the acoustic shock waves and suggested that collapse of the bubble generated by electrohydraulic probes may have local effects due to a cavitation-like mechanism.

Animals↗
PubMed1990

Ly1 and V-gene expression among hybridomas secreting natural autoantibody.

This report presents evidence that multispecific natural autoantibodies (NAAb) arise from both Ly-1+ and Ly-1- B lymphocyte subsets based upon detection of mRNA transcript of Ly1 gene by Northern blotting among hybridomas from several mouse strains. Newborn Xid mice also possess B cells transcribing the Ly-1 gene that secrete multispecific NAAbs. Different VH and VK gene families were expressed at random in both Ly-1+ and Ly-1- hybridoma clones secreting NAAbs. Certain VK gene families VK1, -8, -9, -10 and -19, were preferentially used by NAAbs. No particular VH:VK pairings were observed among NAAbs multispecifically reactive with DNA and cytoskeleton proteins. The NAAbs reactive with BrMRBC exhibited predominant pairing between VH11:VK9 gene families, although, for the first time, we noted the participation of VK1, -10 and -19 gene families in encoding this autoantibody specificity.

Animals↗
PubMed1990

Acute chagasic cardiopathy produced by a strain of Trypanosoma cruzi (type I) in an experimental model.

We have carried out a study of the tissular tropism of the strain Y of T. cruzi considering that the different strains of T. cruzi show a great instability in their pathogenic properties with the aim of proving that the classifications of his parasite based in its tissular tropism are not reliable given that these characteristics are subject to change as can be seen by comparing our results with those of other authors. In our study, the Y. strain of T. cruzi shows a strong pancytotropic action, specially with marked cardiotropic aspects. The lack of affectation in the lymphatic ganglion and the small proportion of spleen lesions (8%) as well as the absence of pseudocysts at this level is surprising in a strain which was described as eminently reticulotropic. Our data show that this strain produces cardiac pseudocysts without lesions of the parasitized muscle fiber. The above mentioned data evidence that the biological behavior of a strain and specially its tissular tropism are susceptible to present variations with time.

Acute Disease↗
PubMed1990

Genetic organization of the cellulose synthase operon in Acetobacter xylinum.

An operon encoding four proteins required for bacterial cellulose biosynthesis (bcs) in Acetobacter xylinum was isolated via genetic complementation with strains lacking cellulose synthase activity. Nucleotide sequence analysis indicated that the cellulose synthase operon is 9217 base pairs long and consists of four genes. The four genes--bcsA, bcsB, bcsC, and bcsD--appear to be translationally coupled and transcribed as a polycistronic mRNA with an initiation site 97 bases upstream of the coding region of the first gene (bcsA) in the operon. Results from genetic complementation tests and gene disruption analyses demonstrate that all four genes in the operon are required for maximal bacterial cellulose synthesis in A. xylinum. The calculated molecular masses of the proteins encoded by bcsA, bcsB, bcsC, and bcsD are 84.4, 85.3, 141.0, and 17.3 kDa, respectively. The second gene in the operon (bcsB) encodes the catalytic subunit of cellulose synthase. The functions of the bcsA, bcsC, and bcsD gene products are unknown. Bacterial strains mutated in the bcsA locus were found to be deficient in cellulose synthesis due to the lack of cellulose synthase and diguanylate cyclase activities. Mutants in the bcsC and bcsD genes were impaired in cellulose production in vivo, even though they had the capacity to make all the necessary metabolic precursors and cyclic diguanylic acid, the activator of cellulose synthase, and exhibit cellulose synthase activity in vitro. When the entire operon was present on a multicopy plasmid in the bacterial cell, both cellulose synthase activity and cellulose biosynthesis increased. When the promoter of the cellulose synthase operon was replaced on the chromosome by E. coli tac or lac promoters, cellulose production was reduced in parallel with decreased cellulose synthase activity. These observations suggest that the expression of the bcs operon is rate-limiting for cellulose synthesis in A. xylinum.

Arabidopsis Proteins↗
PubMed1990

Psi[CH2O] pseudodipeptide synthesis. An improved approach which allows absolute configuration determination.

An improved way to obtain psi[CH2O] pseudodipeptide units is proposed, involving an intramolecular Williamson's reaction, with displacement of bromine by an alkoxide, instead of the classical intermolecular one. Until now, psi[CH2O] pseudodipeptide synthesis done by this new method, has used a protected form of the amino alcohol hydroxyl group to prepare the acyclic precursor. In the present paper, the use of an active ester of the brominated carboxylic acid avoids this protection step. The pseudodipeptides AcGly psi[CH2O]-D,L-Ala-OH and Ac-Ser(Bzl) psi [CH2O]-D,L-Ala-OH were obtained in high yields, through a delta-lactam intermediate, which furthermore allows the determination of the absolute configuration of compounds using HPLC and appropriate nuclear magnetic resonance (NMR) techniques.

Chemical Phenomena↗
PubMed1990

Minimally invasive treatment of ureteric calculi using modern techniques.

Between July 1985 and July 1986, 226 upper and 62 distal ureteric calculi were treated. In situ extracorporeal shockwave lithotripsy (ESWL) is the treatment of choice for upper and distal ureteric calculi, with success rates of 81 and 76% respectively. Retrograde manipulation of the calculus was undertaken only when in situ ESWL was impossible because of difficulty in localisation. Although ESWL after successful mobilisation was successful in 95% of patients, retrograde mobilisation was possible in only 80%. Antegrade ureterorenoscopy via a percutaneous nephrostomy was performed to avoid open surgery if retrograde mobilisation was not feasible, and was successful in 90%. Two second generation lithotripters, the modified Dornier HM3+ and the Wolf Piezolith 2200, both suitable for treatment without anaesthesia, were compared in terms of efficacy. In situ ESWL of upper ureteric calculi was successful in 70.6% with the HM3+ and 37.2% with the Piezolith 2200. In situ ESWL of middle ureteric calculi was successful in 81.8% with the modified HM3+, while in situ treatment of middle ureteric calculi was impossible with the Piezolith 2200 because of inadequate ultrasound localisation. Distal ureteric calculi were treated successfully in 71.4% with the modified Dornier HM3+ and in 64% with the Piezolith 2200. We report our experience of ESWL using the prone position for iliac ureteric calculi; 8 of 10 patients were treated successfully in situ.

Humans↗
PubMed1990

The LY-1 gene expression in murine hybridomas producing autoantibodies.

Studies presented here demonstrate the expression of the Ly-1 gene and the detection of the Ly-1 cytodifferentiation antigen in murine hybridomas producing autoantibodies. We examined the transcription of the Ly-1 gene in thymocytes and 140 hybridomas producing autoantibodies of various specificities which were obtained from normal and autoimmune disease prone mouse strains. As previously demonstrated thymocytes stain brightly for Ly-1 by immunofluorescence and express Ly-1 transcripts. In our panel of hybridomas producing autoantibodies Ly-1 transcripts were detected in 31 (45%) out of 69 NZB hybridomas and 7 (88%) out of 8 viable motheaten hybridomas. S1 nuclease protection experiments showed that Ly-1 transcripts detected in thymocytes and B cells are the product of the same gene. The B cell transcripts are functional since immunofluorescence and Western data presented here detected the Ly-1 protein in hybridomas cells which were found to transcribe the Ly-1 gene. Interestingly a polymorphic transcription of the Ly-1 gene was observed in B cells and B cell hybridomas as compared to thymocytes. Our results obtained in the hybridoma system firmly establish a major contribution of the Ly-1 B cell subset to the production of DNA specific autoantibodies and a smaller contribution to the production of rheumatoid factors and "natural", multispecific autoantibodies.

Animals↗
PubMed1990

Ten-year follow-up of worksite hypertension control programs.

We have analyzed the control of hypertension and the demographics of 898 actively treated (AT) (visits within past 12 months) and inactive patients (IAT) (no visit for at least 12 months) in six worksite hypertension programs established in 1977. Results were analyzed using Student's t test and correlation coefficients. Patients are treated at the worksites by a nurse-physician team using a stepped-care protocol. In the AT group (n = 436), the mean age was 52 +/- 0.5 years, initial blood pressure (BP) was 152 +/- 1/97 +/- 0.5 mm Hg, and current BP was 136 +/- 0.7/86 +/- 0.04 mm Hg (p less than 0.001). Of the 436 patients, 194 were men and 242 were women (217 Caucasian and 156 black). In the IAT group (n = 462) mean age was 51 +/- 0.5 years, initial BP was 154 +/- 1/99 +/- 0.5 mm Hg, and last BP was 138/88 +/- 0.4 mm Hg (p less than 0.001). Of these, 171 were men and 291 were women (238 Caucasian and 171 black). No differences in initial and current BP were noted when comparing the AT with the IAT group. The percent of Caucasian (43%) and blacks (36%) men in the AT group was similar to those in the IAT group (37%). Control of hypertension at worksites where blacks predominate was similar to sites where Caucasians predominate. We conclude that worksite control of hypertension over a 10-year period maintains approximately 50% of the initial population under treatment. Control rates greater than 80% to less than 90 mm Hg diastolic are present despite heterogeneity in demographics.

Black People↗
PubMed1990

ESWL for ureteral calculi. Using the Dornier HM 3, HM 3+ and Wolf Piezolith 2,200.

In a one year period from July 1985 to July 1986 226 upper and 62 distal ureteric calculi were treated. In situ ESWL represents the therapy of first choice for upper and distal ureteric calculi with a success rate of 81% and 76% respectively. Retrograde mobilization of the calculus was used only in cases where in situ ESWL was impossible because of localization difficulties (obesity, stone close to the spine, skeleton deformation). Although ESWL after successful mobilization succeeded in 95%, retrograde mobilization was possible only in 80%. Antegrade ureterorenoscopy via percutaneous nephrostomy was performed to avoid open surgery after impossible retrograde mobilization and succeeded in 90%. Two second generation lithotripters suitable for treatments without invasive forms of the anesthesia, the modified Dornier HM 3- and the Wolf Piezolith 2,200 were compared in terms of efficacy for ureteric calculi. In situ ESWL was successful with the Piezolith 2,200. In situ ESWL of middle ureteric calculi was successful 81.8% with modified HM 3+, while in situ treatment of middle ureteric calculi was impossible with the Piezolith 2,200 due to insufficient localization with ultrasound of middle ureteric calculi were treated successfully in 71.4% with the modified Dornier HM 3+ and in 64% with the Piezolith 2,200. First clinical experience of ESWL in prone position for iliac ureteric calculi was reported. 8 of 10 cases were treated successfully in situ.

Humans↗
PubMed1990

[Electric toothbrushes--manual toothbrushes, a comparison].

This study covering a period of almost 16 weeks shows that manual tooth cleaning must be regarded as somewhat superior to electric tooth-brushes in terms of the plaque index. Concerning the more important sulcus bleeding index, the electric tooth-brush leads to better results. This, however, only after at least two weeks of "familiarisation" of the patients with the electric tooth-brush, and after a minimum follow-up time of three to five weeks! This is why another quite important conclusion should be drawn from this study: studies of this type should not be planned for too short a period, i.e. for at least 12 weeks.

Humans↗
PubMed1990

Proteases in malaria-infected red blood cells.

The discrimination between erythrocyte and Plasmodium proteases is now made easier by using synthetic fluorogenic substrates, high-pressure liquid chromatography, reliable methods of cell preparation, as well as radiolabeled extracts from in vitro cultures of P. falciparum. The reinvasion process of an erythrocyte by a merozoite involves specific proteinases, which were recently identified using fluorogenic peptidyl-AEC substrates and by analysis of schizont and merozoite extracts with the gelatin-SDS-PAGE method. The biological targets of both host and parasite proteinases are not yet well characterized because Plasmodium-infected red blood cells contain at least four compartments with different pH values, which could modulate the proteinase activities according to their pH range activity. The processing of the precursor for the major merozoite surface antigens involves cleavage of very specific peptidic bonds by, so far unknown, proteinases. The depletion of the erythrocyte cytoskeleton could depend on a 37 kD proteinase, which cleaves spectrin and the 4.1 component, as shown in P. berghei and P. falciparum species. In contrast to leupeptin, which inhibits the merozoite release from schizont-infected erythrocytes, the structural inhibitor analogous to the Val-Leu-Gly-Lys (or Arg) P. falciparum neutral proteinase substrates appears to block the invasion step of erythrocytes by merozoites and may open new trends in chemotherapeutical strategies.

Animals↗
PubMed1990

Minimal invasive therapy of ureteral calculi using modern techniques.

In a one year period from July 1985 to July 1986, 224 upper and 62 distal ureteric calculi were treated. In situ ESWL represents the therapy of first choice for upper and distal ureteric calculi with a success rate of 81% and 76%, respectively. Retrograde mobilization of the calculus was used only in cases where in situ ESWL was impossible because of localization difficulties (obesity, stone close to the spine, skeleton deformation). Although ESWL after successful mobilization succeeded in 95%, retrograde mobilization was possible only in 80%. Antegrade ureterorenoscopy via percutaneous nephrostomy was performed to avoid open surgery after impossible retrograde mobilization and succeeded in 90%. Two second generation lithotripters suitable for treatments without invasive forms of anesthesia, the modified Dornier HM3+ and the Wolf Piezolith 2200, were compared in terms of efficacy for ureteric calculi. In situ ESWL was successful for upper ureter calculi in 70.7% with the HM3+ and 37.9% with the Piezolith 2200. In situ ESWL of middle ureteric calculi was successful in 81.8% with the modified HM3+, while in situ treatment of middle ureteric calculi was impossible with the piezolith 2200 due to insufficient localization of middle ureteric calculi with ultrasound. Distal ureteric calculi were treated successfully in 71.4% with the modified Dornier HM3+ and in 64% with the Piezolith 2200. Our initial clinical experience with ESWL in the prone position for iliac ureteric calculi is reported. Eight of 10 cases were treated successfully in situ.

Humans↗