Biomedical subjects

A Holmberg

Publications and source records attributed to A Holmberg.

9 recordsLinked to original sources

PubMed1992

Automated magnetic preparation of DNA templates for solid phase sequencing.

An integrated protocol for solid-phase DNA sequencing using a robotic work station is described involving magnetic separation of DNA and analysis of the sequencing product by electrophoresis with automated detection of the fluorescently labeled fragments. The method, which is based on magnetic beads in combination with streptavidin-biotin technology, can be used for sequencing both genomic and plasmid DNA. The DNA template is obtained by the polymerase chain reaction (PCR). Protocols to prepare five and ten immobilized samples is described, giving 10 and 20 single-stranded templates, respectively. The magnetic purification steps are performed in a microtiter plate and this allows for an integrated scheme involving a subsequent procedure for automated primer annealing and sequencing reactions. Here, the procedure is examplified by direct genomic sequencing of DNA in blood sample from a human immunodeficiency virus (HIV)-infected patient and a cloned human antibody DNA fragment using fluorescently labeled sequencing primers.

Automation↗

PubMed1992

Intraperitoneal 5-fluorouracil in the management of colorectal liver cancer.

Twenty-five patients with colorectal liver metastases had a subcutaneous portal connection with a peritoneal catheter implanted for the intraperitoneal (i.p.) administration of 5-fluorouracil (5-FU). In five patients, the malignant disease rapidly progressed and the implanted catheter system was never used. Among the remaining 20 patients, seven patients had i.p. 5-FU as adjuvant treatment following liver resection and 13 patients received palliative chemotherapy (5-FU) owing to unresectable liver metastases. 5-FU was administered on a regular basis every 4 to 6 weeks by continuous infusion of 1000 mg/day (approximately 15 mg/kg/day) for 5 days. In seven patients, i.p. chemotherapy was managed on an outpatient basis. In general, i.p. 5-FU treatment was well tolerated with only minor abdominal complaints during the initial treatments. No definite effect on survival has been noted. All patients (n = 13) receiving palliative i.p. 5-FU died after a median of 4 (range 1.5-18) months. Two patients receiving adjuvant chemotherapy died owing to recurrence after 20 and 23 months, while five patients are alive, two with recurrent disease and three without, after 14-35 months.

Adult↗

PubMed1991

Electrochemical detection of proteins in high-performance liquid chromatography using on-line, postcolumn photolysis.

Direct detection of proteins in high-performance liquid chromatography electrochemistry (LCEC) is difficult. By using on-line, postcolumn photolysis, proteins now can be detected by LCEC at microgram per milliliter levels. The compatibilities of size exclusion chromatography (SEC), reversed-phase chromatography (RPC), ion-exchange chromatography (IEC), and hydrophobic interaction chromatography (HIC) with photolysis-electrochemical detection is described for proteins together with the analytical figures of merit. Inherent from the advantages of electrochemical detection, the method is sensitive and selective.

Chromatography, High Pressure Liquid↗

PubMed1991

Binding of epidermal growth factor-dextran conjugates to cultured glioma cells.

Some gliomas, melanomas and squamous carcinomas have large numbers of EGF receptors which could, in these cases, be used for targeting with toxic agents. We investigated whether EGF could be conjugated to dextran, which is a suitable carrier for toxic agents, without losing its ability to bind to the receptor. Dextran of 20 kDa molecular weight was activated with I-cyano-4-dimethylamino pyridinium tetrafluoroborate (CDAP) yielding highly active pyridinium-isourea derivatives. EGF was coupled to the activated dextran through the amino terminus and glycine was added to block residual activity. The EGF-dextran conjugate was, after purification on Sephadex G25 and Sephacryl 200 columns, tested for its receptor binding properties on human malignant glioma, U343MGaC12:6, cells. The conjugate inhibited binding of 125I-EGF in a competitive assay, showing that the binding was receptor-specific. Dextran conjugated with glycine, without EGF, had no inhibitory effect. The conjugate was radio-labelled either on the EGF part with 125I or on the dextran part with 3H-glycine, and the internalization patterns were compared to the internalization of 125I-EGF. The radioactivity of the conjugates remained cell-associated for more than 20 hr, regardless of whether the radioactivity was on the EGF or on the dextran part, while the radioactivity of unconjugated EGF rapidly disappeared from the cells. Most of the cell-associated radioactivity was, at all analysed time intervals, located intracellularly. Thus, it seems promising to use dextran, conjugated with EGF, as a carrier of, for example, toxic radioactive nuclides.

Dextrans↗

PubMed1991

Ultrastructural changes in the gracile nucleus of the rat after sciatic nerve transection.

Ultrastructural changes in the gracile nucleus of the rat have been examined after peripheral nerve injury. The sciatic nerve of adult rats was transected at mid-thigh level, and after survival times ranging from 1 day to 32 weeks sections from the gracile nucleus were prepared for electron microscopic examination. Unoperated animals served as controls. Atypical profiles were regularly observed in the experimental cases at post-operative survival times from 3 days up to 32 weeks. It was sometimes not possible to classify these as preterminal axons or terminals, because synaptic contacts could not be identified. The two most common changes throughout the entire post-operative period were greatly expanded myelinated axons, or unmyelinated profiles containing numerous mitochondria, osmiophilic dense bodies and vacuoles. Atypical profiles were occasionally observed in unoperated control animals. The results clearly show that various types of degenerative changes occur in the gracile nucleus after peripheral nerve injury. These changes differ markedly from previously described transganglionic changes in other systems. It cannot be excluded that some of the changes reflect growth-related reactions, although the typical features of axon regeneration could not be found.

Animals↗

PubMed1990

A superficial corneal lesion of unknown origin.

Three patients are described showing corneal changes of unknown origin previously not described. The changes consist of discrete opacities mostly located in the epithelium of the cornea. The opacities are arranged in a continuous are originating from the limbus with the vertex extending towards the optic zone. The cornea inside and outside the arc was normal during the early stages of the disease. In two of the cases a progress of the changes were recorded and a stromal opacity developed inside the arc. The three cases were all unilateral. Bacterial and fungal cultures, virus isolation, several blood tests, serology and immunological tests have been negative. Light- and electron microscopy of biopsied material show intracellular specific epithelial cell changes in the form of perinuclear vacuoles. None of the treatments tried were successful.

Adult↗

PubMed1990

Implantable drainage after major abdominal surgery in compromised patients.

The risk of superinfection following routine abdominal drainage after major surgery is debated. Especially in patients with malignant diseases and a compromised host defense, this might be a factor increasing morbidity and mortality. During a 3-year period (1986-1988) 41 patients operated on for malignant abdominal conditions received a peritoneal catheter connected to a subcutaneous portal inserted in order to participate in a trial on postoperative intraperitoneal chemotherapy using 5-Fluorouracil. No abdominal drains were inserted. In 15 patients, the subcutaneous portal was used for evacuation of postoperative fluid accumulation within the abdomen. The mean age was 53 (range 41-70) years. Inserted catheters were used for drainage up to 14 days postoperatively. The daily amount of fluid drained varied from 20 to 2,000 ml with a mean of 610 ml/patient and day. One patient required removal of the catheter due to infection around the subcutaneous chamber. Otherwise, the catheter system was not associated with any other complications or complaints. One patient developed a postoperative left subphrenic abscess drained percutaneously by the guidance of ultrasonography, a complication that could not be attributed to the catheter system but merely to the major operation per se. An implantable device for peritoneal access thus also seem useful for drainage of postoperative fluid collection, as evaluated in this preliminary report.

Abdominal Neoplasms↗

PubMed1989

Heparin surface modified intraocular lenses implanted in the monkey eye.

The biocompatibility of heparin surface modified poly(methyl methacrylate) intraocular lenses (IOLs) was evaluated in two experiments following implantation in the anterior and posterior eye chambers of adult cynomolgus monkeys. Throughout the study, large inflammatory cells and prominent pigment deposits were seen on the unmodified lenses, whereas the heparin surface modified IOLs remained almost free of precipitates. Similarly, fewer posterior synechias were observed in eyes implanted with surface modified IOLs in the posterior chamber than in eyes implanted with control lenses. Histopathological examination of enucleated eyes confirmed the clinical findings. These experiments strongly support the idea that surface modification with heparin is a useful way to reduce clinical complications following cataract surgery with IOL implantation.

Animals↗

PubMedDate not supplied

Semi-automated solid-phase DNA sequencing.

Increasing the efficiency of DNA sequencing necessitates the development of systems which reduce the need for manual operations by integrating template preparation, sequencing reactions, product separation and detection. A semi-automated system, whereby PCR-amplified biotinylated genomic or plasmid DNA is immobilized on streptavidin-coated magnetic beads, has been developed.

Automation↗