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Biomedical subjects

K Martin

Publications and source records attributed to K Martin.

At least 217 records · Page 12Linked to original sources
PubMed1986

The DNA loop model for ara repression: AraC protein occupies the proposed loop sites in vivo and repression-negative mutations lie in these same sites.

Two sets of experiments have been performed to test the DNA loop model of repression of the araBAD operon of Escherichia coli. First, dimethyl sulfate methylation protection measurements on normally growing cells show that the AraC regulatory protein occupies the araI site in the presence and absence of the inducer arabinose. Similarly, the araO2 site is shown to be occupied by AraC protein in the presence and absence of arabinose; however, its occupancy by AraC is greatly reduced when araI and adjacent sequences are deleted. Thus, AraC protein binds to araO2 cooperatively with some other component of the ara system located at least 60 base pairs away. Second, the mutational analysis presented here shows that the DNA components required for repression of araBAD are araI, araO2, and perhaps the araBAD operon RNA polymerase binding site.

AraC Transcription Factor↗
PubMed1986

Detection of carriers of human Duchenne muscular dystrophy by freeze-fracture analysis of erythrocyte plasmalemmal intramembrane particles.

Critical examination of plasma membrane particles on fracture faces of erythrocyte plasma membranes of human obligate carriers of Duchenne muscular dystrophy, control patients, and a patient afflicted with Duchenne muscular dystrophy revealed a 32% decrease in the number of intramembrane particles in erythrocytes of carriers compared with erythrocytes sampled from control patients. These results support the notion that quantitative analysis of intramembrane particles in freeze-fractured erythrocyte plasma membranes represents a new, rapid, simple, and highly accurate diagnostic tool for detection of carriers of human Duchenne muscular dystrophy.

Cell Membrane↗
PubMed1986

Differential biological effects of calcitonin and parathyroid hormone on isolated perfused bone.

These studies examine the release of 3',5'-cyclic adenosine monophosphate (cyclic AMP) from isolated perfused canine bones in response to synthetic bovine parathyroid hormone (syn b-PTH 1-34) and human calcitonin (hCT). Bones for perfusion were obtained from three groups of dogs: control (n = 11); thyroparathyroidectomized (n = 7), and mithramycin-treated thyroparathyroidectomized animals (n = 5). The results indicate that PTH causes a greater release of cyclic AMP from adult bones than CT; the addition of the two hormones simultaneously results in a synergistic rather than an additive effect; mithramycin inhibits the cyclic AMP response to calcitonin; and thyroparathyroidectomy decreases the cyclic AMP release in response to CT stimulation, suggesting that the cells (osteoclast-like) that respond to CT have an impaired response in the absence of PTH; acute TPTX does not affect the response of the cell populations of adult bones to PTH.

Animals↗
PubMed1986

[Gorham-Stout syndrome of the mandible].

A 16-year-old female complained of loosening of several teeth in the lower jaw. Radiography revealed bone resorption of the tooth sockets. The osteolytic process extended throughout the alveolar crest of the mandible and caused a complete loss of teeth within 2 years. Microscopic sections showed angiomatous tissue of Gorham-Stout-syndrome. Radiotherapy with 35 Gy controlled the mandibular osteolysis. Recurrent meningitis and osteolytic defects of the frontal skull base hint at an additional manifestation of the disease at this site.

Follow-Up Studies↗
PubMed1985

Pseudomonas dermatitis associated with a swimming pool.

One hundred forty-seven (66%) of 224 scouts and chaperons were interviewed after a weekend visit to a dude ranch in upstate New York. One hundred seventeen (80%) complained of papular rashes or eye and ear inflammation. Onset of illness occurred within 24 to 48 hours of arrival at the ranch. After controlling for participation in other available activities, only swimming was found to be associated with illness. Pseudomonas aeruginosa serotype 0 11 grew from a culture of pool water and from 17 cultures of skin, eye, and ear lesions in visitors to the ranch. Follow-up was obtained for 76 of the affected persons for whom initial information was available. Mean duration of illness was 14.5 days (range, one to 40+ days). The recurrence rate was 24%.

Adult↗
PubMed1985

A model for de novo synthesis and assembly of tight intercellular junctions. Ultrastructural correlates and experimental verification of the model revealed by freeze-fracture.

The structure and function of intercellular tight (occluding) junctions, which constitute the anatomical basis for highly regulated interfaces between tissue compartments such as the blood-testis and blood-brain barriers, are well known. Details of the synthesis and assembly of tight junctions, however, have been difficult to determine primarily because no model for study of these processes has been recognized. Primary cultures of brain capillary endothelial cells are proposed as a model in which events of the synthesis and assembly of tight junctions can be examined by monitoring morphological features of each step in freeze-fracture replicas of the endothelial cell plasma membrane. Examination of replicas of non-confluent monolayers of endothelial cells reveals the following intramembrane structures proposed as 'markers' for the sequential events of synthesis and assembly of zonulae occludentes: development of surface contours consisting of elongate terraces and furrows (valleys) orientated parallel to the axis of cytoplasmic extensions of spreading endothelial cells, appearance of small circular PF face depressions (or volcano-like protrusions on the EF face) that represent cytoplasmic vesicle-plasma membrane fusion sites, which are positioned in linear arrays along the contour furrows, appearance of 13-15 nm intramembrane particles at the perimeter of the vesicle fusion sites, and alignment of these intramembrane particles into the long, parallel, anastomosed strands characteristic of mature tight junctions. These structural features of brain endothelial cells in monolayer culture constitute the morphological expression of: reshaping the cell surface to align future junction-containing regions with those of adjacent cells, delivery and insertion of newly synthesized junctional intramembrane particles into regions of the plasma membrane where tight junctions will form, and aggregation and alignment of tight junction intramembrane particles into the complex interconnected strands of mature zonulae occludentes. The distribution of filipin-sterol complex-free regions on the PF intramembrane fracture face of junction-forming endothelial plasmalemmae corresponds precisely to the furrows, aligned vesicle fusion sites and anastomosed strands of tight junctional elements.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

[Amniocentesis under permanent ultrasonic control--advantages of a special procedure].

Advocates of the so-called "free hand technique" in amniocentesis argue against permanent sonographic control as follows: "Free hand technique" is the only method enabling vertical guiding of the puncture needle between abdominal wall and amniotic cavity, and hence to cover the shortest distance with the lowest risk of traumatisation. "Free hand technique" is the only method permitting sensitive guiding of the needle in amniocentesis, since the puncturing doctor can use both hands without requiring one hand for sonographic examination. Amniocentesis under permanent sonographic control is claimed to raise serious problems in guaranteeing the necessary sterility. The authors present a modification of the puncture method with permanent sonographic control. This does away with all of the above arguments against permanent sonographic control, whereas all of its obvious advantages are retained (greater safety, less risk of injury). The method employs a fixation scaffolding and an aiming groove for routine sector scanning (Figures 1 and 2). The entire system is covered in a sterile manner by a pasted-on foil sheeting after having introduced the sonographic contact gel. The only contact medium for the skin is a disinfecting agent enabling satisfactory imaging (Figure 4). This method offers the following advantages over the methods using conventional puncture soundheads: Better possibility of disinfection. No rigid guiding of needle, and hence correction can be effected even during puncture. Adjacent levels can be observed by free displacement of scanner and needle. Modifiable puncture angle in respect of skin and uterus. The fixation scaffolding does away with the need for an assistant, and enables tremor-free fixation of the scanner during puncture.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniocentesis↗
PubMed1985

Electron microscopic visualization of trp operon expression in Salmonella typhimurium.

Transcriptional activity of plasmids carrying wild-type and mutant trp operons was visualized in cell lysates of Salmonella typhimurium. Plasmid and transcription-unit sizes varied with the size of the cloned operon. Following 3-(3-indolyl)acrylic acid derepression, all operons of a particular type exhibited the same high level of transcriptional activity. An estimated 11-14 transcripts must be initiated each minute to maintain the 190-base-pair spacing of RNA polymerases observed on the promoter-proximal half of the wild-type trp operon. A decline in RNA polymerase density was observed on promoter-distal portions of cloned trp operons, which may be attributable to premature transcription termination accompanying translation inhibition due to indolylacrylic acid's interference with normal tryptophanyl-tRNA synthetase activity.

Chromosome Deletion↗
PubMed1985

The distribution of 14C-chloramphenicol in the Japanese quail (Coturnix coturnix japonica).

The distribution of 14C-labelled chloramphenicol after oral and intravenous administration to egg laying Japanese quail was studied by whole-body autoradiography. In the liver, kidneys, gizzard, intestinal contents (bile) and oviduct, the 14C-concentration was higher than that of the blood short time after injection and remained higher than the blood up to 4 days. From 4 hrs, the concentration of 14C in the egg yolks was higher than that of the blood and from 24 hrs the radioactivity in the albumen of the eggs in the oviduct was also higher than that of the blood. The peak concentration in the egg yolk was found in the second egg laid 2-4 days after administration of 14C-chloramphenicol. In the albumen the maximum concentration was found in the first laid egg 24-48 hrs after administration. In the egg yolks, about 30% of the radioactivity represented unchanged chloramphenicol up to 5 days after administration. It was also shown that about 5% of the injected 14C-chloramphenicol was exhaled as 14CO2 during the first 12 hrs and about 37% of the dose was excreted in the combined faeces and urine during the same period of time.

Administration, Oral↗
PubMed1984

Plasma concentration, mammary excretion and side-effects of phenylbutazone after repeated oral administration in healthy cows.

Seven clinically healthy dairy cows were each given 2.5 g phenylbutazone (approximately 5 mg/kg body weight) by oral administration twice daily for 8 days. The concentrations of phenylbutazone in plasma and milk and several blood parameters were studied. The minimum plasma concentration during steady state was 100.4 +/- 7.3 micrograms/ml. During the same period the milk concentration never exceeded 1% of the plasma concentration. The elimination half-life in plasma was 38.6 +/- 3.7 h. Five days after administration had been discontinued, the milk concentration was 0.05 +/- 0.01 microgram/ml. All seven cows were clinically healthy throughout the experiment. The most pronounced side-effect of the blood parameters studied was a decreased concentration of leucocytes to about two-thirds of the control value. This might have a pronounced influence on the effectiveness of the immune system. There was also a significant decrease in total bilirubin indicating a decrease in the breakdown of erythrocytes.

Animals↗