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L Berger

Publications and source records attributed to L Berger.

At least 73 records · Page 4Linked to original sources
PubMed1992

One-step purification of tissue-type plasminogen activator using affinity chromatography with a special monoclonal antibody under mild conditions.

We have previously isolated a monoclonal antibody, designated as 1-3-1, specific for tissue-type plasminogen activator (t-PA). We have shown that t-PA dissociates from 1-3-1 in the presence of the lysine analogue 6-aminohexanoic acid (6-AHA). Here we describe a method for the one-step immunoaffinity purification of t-PA from conditioned melanoma cell medium, using 1-3-1 immobilised on Sepharose under mild elution conditions, favourable for t-PA. The yield of t-PA (antigen or total protein) from a 1-3-1-Sepharose column, when eluted using a buffer supplemented with 0.2 M 6-AHA at neutral pH, was as effective as other buffers that involve a strong pH-change, i.e., pH 2-3. However, the enzymatic activity of the t-PA purified with 6-AHA was 25 to 30% higher, as compared with t-PA eluted using a pH change. This resulted in a markedly higher specific activity of t-PA purified with 0.2 M 6-AHA, as compared with t-PA purified using a strong pH-change. The purity of t-PA, purified using the present method, was very high, as determined by gel electrophoresis. An additional advantage of the present procedure is that the mild elution conditions prolong the column life.

Aminocaproic Acid↗
PubMed1992

Activation of simian virus 40 transcription in vitro by T antigen.

Simian virus 40 is repressed when the viral early gene product large tumor antigen (TAg) binds to specific sites within the viral origin and DNA replication ensues. Late transcription is activated by TAg, even in the absence of viral DNA replication. We show here that TAg produced in human 293 cells can selectively activate Simian virus 40 transcription in a cell-free system. In the absence of DNA binding by TAg, early and late transcription are both activated, as they are in vivo, suggesting that the effect might be mediated by a cellular component(s) utilized by both the early and late promoters. When TAg binds to the viral origin of replication, early transcription is repressed but the late promoter activation is unaffected. Various preparations of TAg differed in their activities, with some able both to bind DNA and to activate transcription and others able to do only one or the other. Since these variations might be explained by variable amounts of associated factors that copurified with TAg, we asked whether a bacterially derived protein could regulate transcription. An NH2-terminal 272-amino-acid fragment of TAg, produced in Escherichia coli as a glutathione S-transferase fusion protein, retains the ability to activate transcription in vitro, similar to that of the full-length protein. Structural features of this region that might be important are discussed.

Amino Acid Sequence↗
PubMed1992

Screening and genetic counselling for relatives of patients with breast cancer in a family cancer clinic.

Family history is the major risk factor in the aetiology of breast cancer. Breast screening is currently available to women from the age of 50 to 64 through the National Breast Screening Programme. There is, however, an equivalent risk of developing breast cancer below 50 for first degree relatives of women diagnosed with breast cancer premenopausally. We have estimated the risk of breast cancer for relatives of women affected at different ages and used these to establish a family cancer clinic offering breast screening based on individual risk. In three years we have seen 851 patients. Compliance for annual radiology was in excess of 83% over this period and of five cancers detected one had a lump at presentation, two developed interval breast lumps, and two were asymptomatic.

Adult↗
PubMed1991

Pharmacokinetic profile of recombinant human insulin-like growth factor I given subcutaneously in normal subjects.

The pharmacokinetic profile of recombinant human insulin-like growth factor I (IGF-I) was studied in healthy volunteers. Following a single subcutaneous injection of 40 micrograms/kg or 80 micrograms/kg, mean serum IGF-I concentrations increased by 150 ng/ml and 245 ng/ml, respectively. During repeated daily injections of 40 micrograms/kg, a steady-state IGF-I level of 150 ng/ml above baseline was reached. Of the pharmacokinetic indices measured, only Tmax varied between single and multiple dose regimens (6.9 hours versus 3.5 hours). No hypoglycaemic symptoms were observed, and after injection of IGF-I no depression of endogenous IGF-I production was observed. Fasting insulin levels were unaltered, but postprandial insulin was lowered by IGF-I with respect to placebo.

Adult↗
PubMed1990

Lampbrush and mitotic chromosomes of the hemiclonally reproducing hybrid Rana esculenta and its parental species.

Mitotic chromosomes of the European water frogs Rana ridibunda and Rana lessonae, the parental species of Rana esculenta, differ significantly in their centromeric regions: when C-banded or when made fluorescent, the centromeres of R. ridibunda (and of ridibunda chromosomes in R. esculenta) are visible as a conspicuous dark granule or as a conspicuous fluorescent spot; the centromeres of R. lessonae (and of the lessonae chromosomes in R. esculenta) are inconspicuous or not fluorescent. Lampbrush chromosomes of these three taxa are described in detail for the first time; those of R. ridibunda and R. lessonae differ significantly in morphostructural characters such as conspicuousness of centromeres and number, form, and location of giant loops as well as in chiasma frequency. Chromosomes of the two parental species can thus be distinguished when present in lampbrush complements of hybrids. Reproduction in both sexes of natural R. esculenta lineages is hemiclonal: only the unrecombined genome of one parental species, usually R. ridibunda, is transmitted to haploid gametes (hybridogenesis). In 18 hybrids from natural populations of Poland, somatic tissues had allodiploid complements with chromosomes from each parental species. In contrast, spermatocytes I of five males and oocytes I of seven of eight females (221 of 222 oocytes) were autodiploid and contained only R. ridibunda chromosomes that formed n bivalents. These 12 hybrids thus were hybridogenetic. A single female hybrid had oocytes I (33 of 34) with genomes of both parental species; they showed various disturbances including tetraploidy, reduced number of chiasmata, and incomplete synapsis resulting in univalents. This individual thus was not hybridogenetic. The irregular lampbrush patterns indicate that such hybrids will have severely reduced fertility and most of their successful gametes will result in allotriploid progeny.

Animals↗
PubMed1990

The relationship of plasma ammonia and lactate concentrations to perceived exertion in trained and untrained women.

The purpose of this study was to investigate the covariance between perceived exertion (recorded using Borg's category-ratio scale CR-10) and the relative oxygen uptake, and lactate and ammonia concentrations in blood from a peripheral vein. Ratings of perceived exertion (RPE) at 25%, 50%, 75% and 90% maximal oxygen uptake and lactate and ammonia concentrations were compared in well-trained women distance runners (n = 22) and untrained women (n = 10). Ammonia concentrations in peripheral venous blood were significantly correlated with RPE (P less than 0.05), both in the trained and untrained women. Differences between the trained and untrained subjects occurred when the ammonia concentration increased to 148 mumol.l-1 in both groups investigated; similarly, the mean RPE correlated significantly with the lactate concentration (P less than 0.05), both in the trained and untrained women and there was a difference in RPE between groups when lactate concentration in the blood had risen to 4.4 mmol.l-1. It would seem that the correlation of blood ammonia and lactate concentrations with RPE during exercise could be a useful indicator of the development of fatigue.

Adolescent↗
PubMed1990

Influences of physical training on the functional changes of young and old red blood cells.

Eleven male elite endurance-trained athletes and 10 male elite strength-trained athletes were compared to a non-trained group of men, to determine the effect of training on some haematological parameters and some indicators of red cell membrane properties. Erythrocytes were age-fractionated by centrifugation in Percoll gradients. It has been found that in the reticulocytes and young erythrocytes of endurance trained athletes activity of acetylcholinesterase (AChE) and concentration of glutathione (GSH) were higher than in strength-trained athletes and control. The red cell osmotic fragility (RCOF) and glycerol lysis time (GLT) of young cells were similar in all investigated groups. The endurance training indicating chronic adaptation mechanisms in significant changes of red cell metabolism but non membrane properties.

Acetylcholinesterase↗
PubMed1990

Splenic abscess in patients on hemodialysis.

We describe two patients on hemodialysis who developed staphylococcal splenic abscesses. Both patients previously had staphylococcal septicemia secondary to infection at the dialysis access site. We postulate that access-site infections may predispose hemodialysis patients to splenic abscess, and that these patients should be investigated for a splenic abscess if they should develop unexplained fever.

Abscess↗
PubMed1989

The effect of nimodipine on the evolution of human cerebral infarction studied by PET.

Fourteen patients were studied by positron emission tomography (PET) within 48 h of onset of a hemispheric ischemic stroke and again 7 days later. After the first set of PET scans, the patients were randomized to receive either nimodipine (n = 7) or a carrier solution (n = 7) by intravenous infusion. The infusions were maintained until the end of the second PET studies. CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), CMRO2, and CMRglc were measured each time. These metabolic and perfusion measurements were performed by standard methods. A surface map of each metabolic and perfusion measurement in the cortical mantle was generated by interpolating between the available slices. The various surface maps representing the physiological characteristics determined in the same or subsequent studies were aligned so that all data sets could be analyzed identically using an array of square regions of interest (ROIs). The functional status of each ROI was recorded at the two intervals following the cerebrovascular accident to characterize the evolution of the infarct, penumbra, and normal brain regions. We presumed the ischemic penumbra to be cortical regions in the proximity of the infarct and perfused at CBF values between 12 and 18 ml/100 g/min on the first PET scan, while densely ischemic regions had CBF of less than 12 nl/100 g/min and normally perfused brain greater than 18 ml/100 g/min. In the densely ischemic zone, CBF increased more in the nimodipine-treated group than in the carrier group. As well, in this region nimodipine reversed the decline in CMRO2 noted in the carrier group, the difference in the changes being significant. In the penumbra zone, comparable trends were noted in OER and CMRO2 but the difference in the changes between the two groups did not reach statistical significance. Changes in CMRglc and CBV were comparable between the two groups in both cortical regions.

Adult↗
PubMed1989

Nimodipine prevents hyperglycemia-induced cerebral acidosis in middle cerebral artery occluded rats.

The effects of acute moderate hyperglycemia on local cerebral pH (LCpH) and local cerebral blood flow (LCBF) were studied in rats infused with glucose before middle cerebral artery (MCA) occlusion, and compared with findings in MCA occlusion alone. The effects of nimodipine infusion on LCBF and LCpH in MCA-occluded hyperglycemic rats were also studied. LCpH and LCBF were determined simultaneously by a double-label autoradiographic technique. Hyperglycemia was induced by an intraperitoneal injection of 2 g/kg D-glucose before MCA occlusion. Nimodipine-treated rats received the drug as an intravenous infusion of 0.5 micrograms/kg/min starting 15 min after occlusion, and ending at decapitation 4 h postocclusion. Cortical LCpH of five structures in the MCA territory of hyperglycemic rats varied between 6.64 +/- 0.04 and 6.72 +/- 0.02 (mean +/- SEM). These values were significantly lower than LCpH in the same ischemic structures in the control rats, which varied between 6.76 +/- 0.04 and 6.82 +/- 0.03 (p less than 0.05 for four of five structures). Cortical LCpH of hyperglycemic nimodipine-treated rats ranged between 6.94 +/- 0.02 and 7.05 +/- 0.02, indicating significant elevations in LCpH (p less than 0.001) compared with the untreated ischemic hyperglycemic animals. LCBF in the ischemic structures was not modified by hyperglycemia or nimodipine treatment. This suggests that nimodipine, by mechanisms other than improvement in blood flow, can prevent the enhanced cerebral tissue acidosis produced by hyperglycemia before incomplete focal ischemia.

Acidosis↗
PubMed1989

Assessment of the viability of haemopoietic cells in the livers of mouse fetuses stored at 4 degrees C. Comparison of various methods of testing their usefulness for haemopoietic transplantation.

The usefulness of three different tests available in experimental haematology for the assessment of the viability of fetal liver cells obtained from murine fetuses kept in refrigerator at 4 degrees C was compared. The usefulness of these cells as potential transplants for haemopoiesis reconstitution was assessed in the test with trypan blue, in the test based on clonal growth of GM-CFU in agar, and in the test of the splenic colony forming ability of CFU-S. Fetuses kept in refrigerator at 4 degrees C tested 16 hours after circulation arrest contained still about 70% of the initial number of the haemopoietic stem cells (CFU-S). The proportion of committed cells belonging to the granulocyto-monopoiesis line (GM-CFU) decreased at the same time to about 25% of the initial number, and was a sensitive indicator of hypoxia of the studied organ. The test for the viability of the cells based on the use of trypan blue gave results reflecting better the changes in the number of CFU-S than GM-CFU cells.

Animals↗
PubMed1988

Calcium channel blockers correct acidosis in ischemic rat brain without altering cerebral blood flow.

We compared the effects of intravenous infusions of 40 micrograms/kg/min verapamil (n = 5), 0.5 microgram/kg/min nimodipine (n = 5), and 5 ng/kg/min prostacyclin (n = 6) and no treatment (n = 6) on local cerebral pH and local cerebral blood flow in middle cerebral artery-occluded rats 90 minutes after the ischemic insult. Local cerebral pH and local cerebral blood flow were determined simultaneously by a double-label autoradiographic technique. The infusions were started 15 minutes after completion of the occlusion and ended at decapitation 90 minutes after completion of the occlusion. Cortical pH for four regions in the ischemic middle cerebral artery territory of rats receiving verapamil or nimodipine was normalized (mean +/- SEM 6.90 +/- 0.02 and 7.01 +/- 0.01, respectively, for the parietal, sensorimotor, frontal, and auditory cortexes), while mean +/- SEM pH in rats receiving prostacyclin was 6.79 +/- 0.01; in untreated rats, mean +/- SEM pH in the same brain regions was 6.72 +/- 0.01. Local cerebral pH in the verapamil- or nimodipine-treated rats was thus significantly different from that in untreated rats (p less than 0.05). Local cerebral blood flow in treated rats was not different from that in untreated ones. Our findings suggest that calcium channel blockers correct ischemic cerebral acidosis by metabolic mechanisms rather than by changes in blood flow.

Acidosis↗