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Biomedical subjects

R Schubert

Publications and source records attributed to R Schubert.

At least 109 records · Page 6Linked to original sources
PubMed1994

[15N-flow after in sacco incubation and feeding of sheep and goats with untreated wheat straw or straw treated with 15N horse urine].

Chopped wheat straw was homogeneously mixed with urine of horses (5.75 gN per 1, 16.88 atom-% 15N-excess) and airtightly stored in plastic containers for 6 months. Three rumen fistulated sheep and goats each were fed with untreated or urine treated straw. Concentrate was added to straw. Untreated and urine treated straw were given in nylon bags and incubated in the rumen of sheep and goats for 1, 3, 6, 12, 24, 48 and 72 hours. A three compartment exponential function was used to fit the measurements of 15N-excess and 15N-amount of bag content. The curves and the calculated partial Y-values of the three compartments show the inflow and outflow of 15N into or from the bags and allow conclusions about the binding of urine N. Most N of urine was not compactly bound by straw during storage. Primarily microbial N was attached to the straw in the rumen. About 6% of urine N were bound more compact to the straw. Similar curves were calculated for 15N-excess and 15N-amount of nylon bags. The curves allow conclusions about tracer flows without quantitative knowledge. There were no significant differences between animal species.

Animal Feed↗
PubMed1994

Studies on the transport in vitro of lysine, histidine, arginine and ammonia across the mucosa of the equine colon.

Discs of stripped mucosa from the proximal ventral colon were prepared immediately after slaughter of 8 Shetland cross-breed ponies. The mucosae were fixed in incubation chambers and used in incubation experiments to study the transmucosal fluxes of the amino acids lysine, histidine and arginine (150 min) and of ammonia (90 min). When the amino acid concentrations in the mucosal solution were in the physiological range (2.8-3.0 mmol/l) no transport to the serosal side of the tissue was found. When the concentrations were raised 10-fold, less than 2% of the mucosal amino acid pool was recovered in the serosal solution. Ammonia was transported across the mucosa at significant rates although only 63% of the ammonia that disappeared from the mucosal solution was found in the serosal solution. The findings show that the equine proximal colon is virtually impermeable to luminal free amino acids whereas ammonia is transported at rates equal to, or higher than those observed with rumen mucosa from sheep.

Amino Acids, Essential↗
PubMed1994

A new method for practicing exploration, dissection, and simulation with a complete computerized three-dimensional model of the brain and skull.

In current practice, anatomical atlases are based on a collection of planar images presented in a book or, recently, stored on digital media. We present a new kind of interactive true three-dimensional (3D) anatomical atlases based on a volume model derived from MRI and CT. The model has a two-layer structure. The lower level is a volume model with a set of semantic attributes connected to each voxel. The semantic attributes are assigned by an anatomist using a volume editor. THe upper level represents a set of relations between these attributes. Interactive visualization tools such as multiple surface display, preparation of transparent material and cutting are provided. It is shown that the combination of this model with advanced tools for volume visualization provides the 'look and feel' of real dissection. The system therefore represents a bridge between real dissection of a cadaver and textbooks and classical atlases of anatomy. First tests have shown that the atlas system may be used successfully for teaching anatomy, but also as a reference for radiologists or surgeons. The powerful underlying data structure potentially includes all classical visual teaching aids. As a replacement of classical atlases, however, spatial resolution has still to be improved.

Anatomy↗
PubMed1993

Destabilization of egg lecithin liposomes on the skin after topical application measured by perturbed gamma gamma angular correlation spectroscopy (PAC) with 111In.

Unilamellar and oligolamellar liposomes were topically applied to the skin of porcine ears. Perturbed angular correlation spectroscopy of 111In-DTPA, initially entrapped into the liposomes, was used to study the release kinetics of the hydrophilic probe. After drying of the liposomal suspensions, a decrease of the time-integrated perturbation factor within 30 min indicated destabilization of the liposomes and total marker release in the upper epidermal layers.

Animals↗
PubMed1993

[3D reconstruction by high resolution MR tomography of the inner ear].

By means of modern 3D-visualization systems it is possible to render detailed reconstructions of very small morphological structures such as the inner ear. Aim of the present study was to demonstrate the imaging quality of a new 3D-segmentation program developed in the University of Hamburg. The investigation was carried out on a high-resolution MR-tomography of the author's labyrinth and facial nerve. The images were obtained with a fast-field-echo technique using a surface coil. 32 axial slices of 1.0 mm thickness were used for reconstruction. Thus it was possible to completely visualize cochlea, semicircular canals and facial nerve. Especially the filiform substructures of the inner ear could reliably be reconstructed. So the content of information of the MR-investigation could be increased by the 3D-technique applied.

Computer Simulation↗
PubMed1993

cGMP-dependent protein kinase activates Ca-activated K channels in cerebral artery smooth muscle cells.

Guanosine-3',5'-cyclic monophosphate (cGMP)-dependent protein kinase (cGMP-PK) plays a central role in the mediation of the vasodilator response to nitric oxide (NO) and other nitrovasodilators. It is unclear whether cGMP-PK affects calcium-activated potassium channels (KCa channels) or any other type of ion channel in smooth muscle. We provide here the first direct evidence that cGMP-PK can activate KCa channels in arterial smooth muscle cells. We demonstrate that NO and a membrane-permeable analogue of cGMP can activate KCa channels in on-cell patches approximately twofold. Furthermore, cGMP-PK, in the presence of ATP and cGMP added directly to the intracellular surface of inside-out patches, increases channel activity by approximately eightfold. These results suggest that cGMP-PK-mediated activation of KCa channels may contribute to the actions of NO and other nitrovasodilators.

Animals↗
PubMed1992

Familial rectal pain: a type of reflex epilepsy?

We studied 2 members of a family suffering from paroxysmal attacks elicited by tactile stimuli. The attacks consist of burning pain of the stimulated body part, followed by either complete collapse or tonic posturing. Noxious stimuli provoke episodes regardless of their somatic location, whereas it is only necessary for nonnoxious stimuli to be applied to specific trigger zones, such as the rectum, to provoke attacks. Episodes are most commonly precipitated by bowel movement, leading to extreme fear of defecation and resultant fecal retention. An ictal electroencephalographic video recording revealed only slowing of the background; however, serum prolactin was significantly elevated postictally. The attacks were completely suppressed by carbamazepine and resumed on discontinuing the medication. These attacks may represent a form of reflex epilepsy manifested by autonomic nervous system dysfunction.

Adult↗
PubMed1991

First results on the incorporation and excretion of 15N from orally administered urea in lactating pony mares.

Two lactating pony mares were given oral offers of 20 g 15N urea [95 atom-% 15N-excess (15N')] on 6 subsequent days. About 80% of the consumed 15N' were excreted via urine and faeces, but only about 2% via milk. The 15N' secreted via milk-lysine only amounted to 0.04% of the 15N' intake. The recovery was about 90% in each case. Tissues with active metabolism had an unexpectedly high labelling (greater than 0.3 atom-% 15N'). The low extent of the conversion of oral urea N into milk-lysine speaks against an essential participation of the enteral synthesis in meeting the amino acid requirement of lactating mares. It was already concluded from this results that the determination of the amino acid requirement will be necessary for this group of performance.

Administration, Oral↗
PubMed1991

[The dynamics of bone apposition in different animal species--a comparative study].

The time of the bone apposition was compared in rats, rabbits and guinea pigs with the aid of enzyme-activity measurements, determination of the proportion of minerals and the judgment of the cell generation. For this intention a defect was made in the distal femur epiphyses at the three species. The animals were observed for a term of 15 weeks. The results showed little differences with regard to the speed of the bone apposition in the three called species. The bone metabolism of rats was higher than those of the other ones. A clear reference value for the enzyme activity to a define point of time of the mineralization could not be ascertained.

Alkaline Phosphatase↗
PubMed1991

[3D displays for craniofacial surgery].

3D visualisation from tomographic image sequences has turned out to be a useful addition to diagnosis and surgical planning in craniofacial surgery. However, its clinical use still suffers from the very large variety of different methods and parameters from which the surgeon may choose. This is true not only of the data acquisition but also for of documentation of the results. Furthermore, there is no standardisation of procedures according to classes of malformations. This paper presents a systematic investigation of these problems. It proposes a standardisation of craniofacial malformations and describes an optimisation of the procedure of 3D visualisation. The procedure described has become a standard tool for craniofacial surgery in our hospital.

Cleft Lip↗
PubMed1990

["Implant"--software for the documentation of statement and course in the special dentist hour consultation of implantology].

A programsystem is presented which supports the attending physician on entering symptoms of clinical and paraclinical parameters. The system runs on personal computer with Z-80 CPU under dBASE II. The program consists of six parts: 1. simple patient data, 2. oral documentation, 3. diagnostical base program, 4. sketch of therapeutics, 5. dispensaire documentation. It aims on the reduction on routine work (e. g. data in- and output) and simple statistical analysis (view of success of several implantationsystems).

Dental Implantation↗
PubMed1989

Non-leaky vesiculation of large unilamellar vesicles (LUV) induced by plasma high density lipoproteins (HDL): detection by HPLC.

Interaction of large unilamellar phosphatidylcholine vesicles (LUV, 75nm) and plasma high density lipoproteins (HDL) resulted in a non-leaky vesiculation of LUV. This vesiculation was detected by a HPLC-system consisting of a combination of three TSK-gel columns (6000PW, 5000PW, 3000SW). With increasing incubation time liposomal [14C]PC, entrapped [3H]inulin, and apoprotein of HDL origin decreased. The decrease was accompanied by a formation of new particles, consisting of liposomal PC and apoprotein. These particles also enclosed [3H]inulin, reflecting a hydrophilic inner space. The formation of the particles reached a maximum after one day of incubation. Retention time was 21 minutes for LUV, 28 minutes for the new particles, and 36 minutes for HDL. In vesicles with membranes consisting of phosphatidylcholine and 30% cholesterol no interactions were observed.

Carbon Radioisotopes↗
PubMed1989

Preparation of hemoglobin-containing liposomes using octyl glucoside and octyltetraoxyethylene.

Hemoglobin (Hb) was encapsulated in phosphatidylcholine vesicles by removal of the detergent n-octyl beta-D-glucoside (OG) or n-octyltetraoxyethylene (C8E4) out of mixed detergent-lipid micelles in Hb solution. Three types of apparatus were used for dialysis. Dialysis buffer flow rates, the surface area of the dialysis membranes, and detergent-lipid interactions determined the rate of dialysis, which influenced liposome size and lamellarity. Slow dialysis led to the formation of multilamellar liposomes, at increased dialysis rates Hb liposomes became smaller and unilamellar. Hb was enclosed at highest concentrations in larger liposomes, which included the negatively charged lipid phosphatidylserine or phosphatidic acid as a membrane component. Co-encapsulation of the allosteric factor inositol hexaphosphate led to oxygen dissociation curve values almost identical to those of whole blood. The oxygen-release capacity of Hb liposome suspensions in the physiological partial pressure range was comparable to whole blood. Storage of Hb liposomes for 2 months leaves oxygen-carrying characteristics virtually unchanged, with met-Hb levels increasing to only 11% of total Hb. Preparation of Hb liposomes by dialysis of octyl glucoside or C8E4 is a mild and efficient method for encapsulation of Hb. Since these Hb liposomes can be produced in scale-up batch sizes, they are a candidate for use as an oxygen-carrying blood surrogate.

Blood Substitutes↗