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Biomedical subjects

J Meier

Publications and source records attributed to J Meier.

At least 91 records · Page 5Linked to original sources
PubMed1990

[Tissue reactions with administration of piezoelectric shock waves in lithotripsy of salivary calculi].

Before clinical application of an extracorporeal piezoelectric lithotripter to treat sialolithiasis, tissue reaction during shockwave application was examined in vitro and in experiments with animals. Application of shockwaves to human tissue in vitro showed neither macroscopic nor microscopic effects. In animal experiments, the acute experiment (16 rabbits, Chinchilla-Bastard) revealed minor bleeding in the parenchyma of the parotid gland, while the chronic experiment (14 rabbits, Chinichilla-Bastard) revealed no morphologic tissue damage to the parotid region of the rabbit, as a result of piezoelectric shockwaves. However, when the eye was placed in the shockwave focal area and the shockwaves were transmitted via the fissura orbitalis to the endocranium, brain damage could be detected morphologically. In conclusion, the authors feel that the clinical application of extracorporeal piezoelectric fragmentation of salivary stones is justified, provided that a reliable positioning of the patient and exact sonographic location of the concrement are possible.

Animals↗
PubMed1989

On the significance of animal experiments in toxinology.

In increasing areas of the world, there is considerable controversy over the use of animals in scientific research. Ethical, scientific and economic reasons require a reduction in animal experiments as well as animal numbers, a refinement of existing methods and, wherever possible, a replacement of in vivo methods by in vitro test systems. By scoping on papers published in Toxicon between 1980 and 1986, the current situation of animal experimentation in toxinology is evaluated. Fundamental research and antivenin production are reviewed and special reference is given to the experiments involved in drug registration by the example of batroxobin, a purified serine proteinase from Bothrops moojeni venom used as a defibrinogenating agent. Although the ethical question is the most important motif, a reduction in the number of animal experiments can be achieved more pragmatically: the scientific community must learn to constantly ask whether the intention behind an experimental series justifies the use of animals or not. This learning process can be supported by special educational programmes at university level, by making financial support dependent on questionnaires concerning the planned animal experimentation, by including respective questions in the application files for grants, and by ethical guidelines that form an integral part in the instruction for authors of scientific journals.

Animal Experimentation↗
PubMed1989

Comparison of three colon cleansing methods: evaluation of a randomized clinical trial with 300 ambulatory patients.

In a prospective randomized clinical trial, three colon cleansing methods for colonoscopy were compared with regard to a) side effects, b) patient acceptance, c) residual liquid and stool during colonoscopy, and d) quality of the examination. The patients were randomly assigned to one of the following three groups for colon preparation: Group 1 (n = 100) 4 liters of Golytely, group 2 (n = 102) 2 liters of Golytely combined with Cascara-Salax, and group 3 (n = 98) X-Prep (a Senna preparation) combined with an enema. X-Prep (group 3) caused significantly more abdominal cramps than 4 liters of Golytely (group 1) or 2 liters of Golytely with Cascara-Salax (group 2) (p less than 0.001). Vomiting was most frequent in group 1 (p less than 0.05 vs. group 3). The patients therefore preferred X-Prep to 4 liters of Golytely (p less than 0.01). The cleanest colon was obtained with 4 liters of Golytely, while 2 liters of Golytely with Cascara-Salax was least efficacious. The quality of the examination was equal in groups 1 and 3, and clearly better than in group 2 (p less than 0.01). We thus conclude that while 4 liters of Golytely and X-Prep plus enema have equivalent cleansing efficacy for colonoscopy, patients judged X-Prep to be less unpleasant.

Adolescent↗
PubMed1989

Sero survey of human immunodeficiency virus infection in women at a family planning clinic: absence of infection in an indigent population in San Francisco.

To determine the seroprevalence of human immunodeficiency virus (HIV) in contracepting women, 1,308 consecutive attendees at an inner-city family planning clinic completed a risk factor questionnaire and were then asked to have an HIV test. None of the 1,000 women tested was seropositive. Preventive efforts in family planning clinics are likely to be productive because few contraceptors, including those with risk factors, are already infected. The factors which determine differences in HIV positivity between childbearing and contracepting women, who are similar in demographic and HIV risk characteristics, warrant further investigation.

Adolescent↗
PubMed1989

[Snake venom proteins in hemostasis: new results].

Biological features of venomous snakes as well as biochemical properties and actions of their venoms which serve for prey acquisition, indicate the vertebrates' haemostasis system as a vulnerable target for snake venom actions. Components exerting a specific, either stimulating or inactivating effect on basal membrane or endothelial cells of the vascular wall, on platelets, on almost every step of plasma coagulation or fibrinolysis respectively, have been isolated and purified from snake venoms. Snake venom proteins acting with a defined specificity on cellular or plasmatic components of the human haemostatic system are being used in coagulation and aggregation tests, in photometric assays in conjunction with chromogenic substrates as well as in immunological systems as biochemical tools for research and diagnostic purposes.

Blood Coagulation↗
PubMed1989

[Extracorporeal piezoelectric lithotripsy of salivary calculi. In vitro studies].

The feasibility of fragmentation of salivary stones by a new extracorporeal piezoelectric lithotripter was investigated. A total of 40 salivary stones were submitted to piezoelectric shockwave treatment. Prior to shockwave application the diameter, weight and volume of all the stones were determined. After shockwave application the chemical composition of the stones was investigated by X-ray diffractometry. Fragmentation was achieved in 35 of 40 (87.5%) stones. Of these 40 stones, 25 (62.5%) were disintegrated adequately (residual fragments less than 1.5 mm). No statistically significant correlation was observed between the number of discharges required for disintegration and the diameter, weight, volume or the chemical composition of the stones.

Humans↗
PubMed1988

The separation of transcriptionally engaged genes.

We have developed a method for the separation of transcriptionally engaged chromatin from inactive genes as well as from active genes which are not being transcribed. This approach is dependent upon the integrity of the growing transcript and is reflected in a significant decrease in the density of the chromatin during transcription. The decrease in density appears to be due to an association between the growing transcript and a large zone of lower density, possibly the nuclear matrix. These interactions are preserved after fixation of the nuclear material with formaldehyde. Hormonal induction of transcriptional activity causes a shift of the genetic material for the stimulated gene from the high density domain to the low density region. The vast majority of the polymerase II which is engaged with the chromosomal material is also found in this lower density zone. We find that most of the fast form of histone acetylation occurs on those histones which are associated with the active chromatin, further supporting the idea that this modification is involved in some way with the transcriptional process. The merits of this approach are discussed, as are the possibilities for its further exploitation.

Animals↗
PubMed1988

Isoelectric focusing of Protac, the protein C activator from copperhead (Agkistrodon contortrix) venom: a note on experimental problems.

The isoelectric point of Protac was recently estimated to be at pH 3. However, further investigations using different experimental procedures revealed that Protac, due to its particular binding properties, is able to form complexes with carrier ampholytes. Thus, the actual isoelectric point of Protac was found to be in the basic region.

Crotalid Venoms↗
PubMed1988

Determination of batroxobin levels in the plasma of guinea pigs after epicutaneous and intravenous applications.

An enzyme immunoassay has been set up to measure batroxobin levels in plasma. This assay allowed the detection of amounts of batroxobin greater than 0.5 ng/ml plasma. After the epicutaneous application of 50 or 100 batroxobin units (BU)/kg body weight, no batroxobin could be detected in plasma samples taken 15, 30, 60, 120 or 240 min after the start of the experiment. In contrast, batroxobin could be detected in plasma samples after i.v. injection of 10 BU/kg body weight.

Animals↗
PubMed1988

Practical application of the protein C activator Protac from Agkistrodon contortrix venom.

The protein C activator Protac from A. contortrix venom is being investigated as a potential antithrombotic agent and as a tool for the preparation of activated protein C. Its established major application is the zymogen activation in functional protein C determinations based on either a clotting assay or a chromogenic substrate technique. The sensitivity of the activated partial thromboplastin time as an indicator reaction for Protac activated protein C depends on the contact activator component of the reagent. Protein C dose-response increased in the following order: kaolin greater than ellagic acid greater than sulfatide. This phenomenon is due to a competition of molecular affinities between Protac, plasma components and the different activating surfaces.

Crotalid Venoms↗
PubMed1987

Characterization of the protein C activator Protac from the venom of the southern copperhead (Agkistrodon contortrix) snake.

A single chain glycopeptide with a molecular weight of approximately 37,000, an isoelectric point of 3.0 +/- 0.2 and a carbohydrate content of approximately 20% was isolated from the venom of the southern copperhead Agkistrodon contortrix contortrix. It was capable of converting zymogen protein C in plasma of man and various vertebrates into its activated form, a serine proteinase which exerts an anticoagulant effect. Conversion of the zymogen protein C into the active proteinase was demonstrated by measuring the prolongation of the activated partial thromboplastin time due to proteolytic degradation of factors Va and VIIIa by the activation product, as well as by direct measurement of the generated enzyme activity by means of a synthetic chromogenic substrate. Intravenous injection of the venom protein C activator into rabbits caused prolonged activated partial thromboplastin time. Repeated subcutaneous injections led to formation of an antibody which formed, with purified protein C activator as well as with crude A. contortrix venom, a precipitating complex devoid of protein C activator potency. As revealed by activity measurements and by immunodiffusion experiments, the venoms of various A. contortrix, A. bilineatus subspecies contain similar protein C activators.

Animals↗
PubMed1986

[Fibrolamellar hepatoma].

Unlike hepatocellular hepatoma (HCC), the so-called fibrolamellar hepatoma (FLH) is found almost exclusively in the non-cirrhotic, non-infected liver. Patient characteristics and the course of the disease in FLH differ markedly from HCC. FLH represents only a small portion of hepatomas in general (approx. 2%), but accounts for over 40% of hepatomas in young adults. We present the case of a 38-year-old woman showing the typical histological findings of polygonal eosinophilic tumor cells and characteristic lamellar bundles of fibrous stroma, which led to the diagnosis of FLH. The approx. 140 cases of FLH published in the world literature are also presented and discussed. The usefulness of additional examinations (neurotensin, vitamin B12 binding capacity and copper stains) is mentioned. The difficulty in diagnosing FLH lies in its histological differentiation from focal nodular hyperplasia. When diagnosed early, however, FLH is characterized by good resectability with a chance of cure or at least a markedly better survival rate than HCC.

Adult↗
PubMed1986

Quantitative glomerular morphology of the normal and diabetic baboon kidney.

This is a study of quantitative glomerular morphology in 14 normal and 6 long-term diabetic female baboons between 3 and 25 years of age. In the normal female baboon, peripheral glomerular capillary basement membrane thickness increased until around 10 years of age, reached a plateau between 10 and 20 years of age, and possibly decreased at 25 years of age. Mean value for young (3 to 7 years of age) and older (10 to 25 years of age) controls were 266 nm and 329 nm respectively. Fractional volumes of mesangial matrix (8.9%) and mesangial cells (6.8%) were not affected by age. Glomerular basement membrane thickness and the volume of mesangial matrix increased progressively in female baboons with poorly controlled pancreatectomy-induced diabetes, while the volume of mesangial cells remained unchanged. After 106 to 145 months of diabetes, glomerular basement membrane thickness and the volume of mesangial matrix were 558 nm and 18.7% respectively. These values were significantly greater than those of the age-matched controlled (p = less than 0.05). By light and electron microscopy, the normal baboon glomerular morphology, morphometric measurements and changes with age were similar to those in man. The renal changes in diabetic baboons were also similar in morphology and rate of development to those of mild to moderate diffuse diabetic glomerulosclerosis in humans, indicating that the baboon is an ideal model for the long-term study of diabetic glomerulosclerosis. The presence of considerable interanimal variability in the degree of glomerulosclerosis attained after prolonged diabetes suggested that glomerulosclerosis progressed at different rates in these models. The reason for this was not apparent.

Aging↗
PubMed1986

Individual and age-dependent variations in the venom of the fer-de-lance Bothrops atrox.

Individual and age-dependent variations in the venoms of 23 specimens of Bothrops atrox were studied using SDS-polyacrylamide gel electrophoresis, isoelectric focusing and different enzymic activity measurements. The electrophoretic patterns showed a decrease in total protein band numbers and a shifting from components with higher to those with lower molecular weights with increasing age of the snakes. The venoms of individuals younger than 12 months showed isoelectric focusing patterns within a pH range of 3.5-6.0, whereas those of older specimens extended from pH 3.5 to 7.0. Individual variations were found in fibrinogen-clotting and fibrinolytic activities. Despite the fact that important quantitative differences were also found in amidolytic activities measured on five chromogenic proteinase substrates, all the venoms showed the same activity profile. Specimens of the oldest age group (8 years) showed absence of some enzymatic activities.

Aging↗