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Biomedical subjects

M Lorentzen

Publications and source records attributed to M Lorentzen.

At least 19 recordsLinked to original sources
PubMed2005

Nanomechanical sensing of DNA sequences using piezoresistive cantilevers.

A microfabricated cantilever with an internal piezoresistive component has been sensitized with thiol tethered ss-DNA strands and utilized for an in situ, label-free, highly specific, and rapid DNA detection assay. The generation of a differential surface stress onto the functionalized cantilever surface upon target recognition has allowed nanomechanical identification of 12-nucleotide complementary DNA probes with single base mismatch discrimination (sensitivity of 0.2 microM). Interestingly, utilization of an overhang extension distal to the surface enhanced the sensitivity to the 0.01 microM level. The cantilever was functionalized by inkjet printing technology. Replacing the capture probe with locked nucleic acid (LNA) resulted in a faster target probe capture kinetics compared to DNA-DNA hybridization. The capabilities of the piezoresistive cantilever indicate future ergonomic convenience via miniaturization alternative to the conventional laser-based detection method for portable on-site applications.

Base Sequence↗
PubMed2004

Bioavailability of selenium from fish, yeast and selenate: a comparative study in humans using stable isotopes.

OBJECTIVE: To measure the bioavailability of selenium from cooked and raw fish in humans by estimating and comparing apparent absorption and retention of selenium in biosynthetically labelled fish with labelled selenate and biosynthetically labelled selenium in brewers yeast. DESIGN: The intervention study was a parallel, randomised, reference substance controlled design carried out at two different centres in Europe. SETTING: The human study was carried out at the Institute of Food Research, Norwich, UK and at TNO Nutrition and Food Research, Zeist, The Netherlands. SUBJECTS: In all, 35 male volunteers aged 18-50 y were recruited; 17 subjects were studied in Norwich (UK) and 18 in Zeist (Netherlands). All of the recruited subjects completed the study. INTERVENTIONS: Biosynthetically labelled trout fish (processed by two different methods), biosynthetically labelled brewers yeast and isotopically labelled selenate were used to estimate selenium apparent absorption and retention by quantitative analysis of stable isotope labels recovered in faeces and urine. Subjects consumed the labelled foods in four meals over two consecutive days and absorption was measured by the luminal disappearance method over 10 days. Urinary clearance of isotopic labels was measured over 7 days to enable retention to be calculated. RESULTS: Apparent absorption of selenium from fish was similar to selenate and there was no difference between the two processing methods used. However, retention of fish selenium was significantly higher than selenate (P<0.001). Apparent absorption and retention of yeast selenium was significantly different (P<0.001) from both fish selenium and selenate. CONCLUSION: Fish selenium is a highly bioavailable source of dietary selenium. Cooking did not affect selenium apparent absorption or retention from fish. Selenium from yeast is less bioavailable.

Adolescent↗
PubMed1993

Xanthogranulomatous cholecystitis. A clinicopathological study of 20 cases and review of the literature.

Xanthogranulomatous cholecystitis (XGC) is a focal or diffuse destructive inflammatory process of the gall bladder, characterized macroscopically by yellowish tumour-like masses in the wall of the gall bladder. Microscopically, it is characterized in the early stages by a large number of foamy histiocytes and acute inflammatory cells. Later stages demonstrate increasing fibrosis. The gall bladder from 20 of 352 consecutive patients subjected to cholecystectomy showed XGC. Gall stones were found in the gall bladder of all 20 patients and in the ductus choledochus in 3 cases. Perforation of the gall bladder was observed at operation in six cases; in one case there was also a fistula to the colon. A perivesical abscess was found in five other cases. Adhesions to the surrounding structures were seen in a total of 16 cases. Pathogenetically, XGC is probably due to an interplay between obstruction of the gall flow, infection with subsequent inflammation, and leakage of gall fluid to the tissue, where histiocytes accumulate and phagocytize the bile pigment, haemosiderin and cholesterol, resulting in the formation of xanthoma cells. The correct diagnosis of XGC is important for several reasons, first and foremost due to the high frequency of complications, but not least because the condition may give rise peroperatively to the suspicion of malignancy. The new laparoscopic method for cholecystectomies further stresses the necessity of correct preoperative diagnosis of complicating disease.

Adult↗
PubMed1992

Phaeochromocytoma--an unusual cause of haematuria.

A patient was admitted to hospital because of haematuria. A papillomatous bladder tumor was removed. Histological examination revealed a phaeochromocytoma. Fourteen days postoperatively the urinary excretion rates of catecholamines were elevated but normalized afterwards. Abdominal computed tomography and metaiodobenzylguanidine scintigraphy were normal. No hypertension or characteristic micturitional attacks preceded removal of the tumor.

Cystoscopy↗
PubMed1991

Anorectal dysfunction in patients with urologic disturbance due to multiple sclerosis.

Anorectal function was evaluated in 11 patients with voiding dysfunction due to multiple sclerosis. In six patients with constipation, three also had symptoms of obstructed defecation and one patient was incontinent due to stercoral diarrhea. One patient was only fecal incontinent and one patient had obstructed defecation as the only symptom. Three patients had no anorectal symptoms. Anal manometry in the women compared with a control group revealed significant lower anal resting and squeeze pressures, although no significant difference of rectal sensation to distention with air was found. Pudendal nerve terminal latencies were obtained in seven patients and were all normal. In four patients latency could not be demonstrated due to poor contraction of the sphincter on stimulation of the pudendal nerve. Two of these patients were incontinent and two had both constipation and obstructed defecation. It is concluded that patients with voiding symptoms due to multiple sclerosis often reveal anorectal symptoms or motility disorders. Although anal sphincter function is reduced, fecal incontinence is not prevalent in this group. The reason for this lies probably in the fact that many of the patients are constipated, thus securing fecal continence.

Adult↗
PubMed1990

Influence of peptides on anorectal function.

Immunohistochemical and immunochemical studies on biopsies from the human rectum and anal canal have shown several regulatory peptides present in the muscle layers and the mucosa, suggesting a regulatory action on defecation. This view has been supported by studies of anorectal function in man during administration of different peptides. The physiological implications of these observations remain obscure.

Anal Canal↗
PubMed1989

Influence of gastrointestinal neuropeptides on the anal canal.

To evaluate the possible effect of gastrointestinal neuropeptides on anal function, the effect of somatostatin, enkephalin, VIP, and substance P on anal canal pressure and electromyographic response of the external anal sphincter was studied in healthy subjects. Enkephalin and somatostatin elicited a significant decrease in anal canal pressure after a bolus injection of 1 microgram/kg body weight whereas VIP and substance P had no effect. Future studies must show whether these effects are of pharmacologic importance and if these peptides participate in the physiologic regulation of anorectal function.

Adolescent↗
PubMed1989

Implantation of artificial sphincter for anal incontinence. Report of five cases.

The implantation of an artificial anal sphincter in five patients with anal incontinence of neuromuscular origin is described. The prosthesis, an AMS 800 artificial urinary sphincter (American Medical Systems), worked well with solid or semisolid stool, but less satisfactorily when diarrhea was present. Manometric and defecographic studies seem to indicate that the effect of the prosthesis may be ascribed partly to maintenance of an acute anorectal angle even during straining.

Adult↗
PubMed1988

Xanthogranulomatous inflammation of the female genital tract.

We describe three cases of xanthogranulomatous inflammation in the female genital tract--one affecting endometrium, tube and ovary, one affecting tube, ovary and parametrium and one confined to the endometrium. To date, xanthogranulomatous inflammation in the female genital tract has been reported in a total of 19 cases including the present three. The inflammation most often affects the endometrium but involvement of the vagina, cervix, fallopian tube and ovary may also occur.

Aged↗
PubMed1987

Implantation of artificial sphincter for anal incontinence.

The implantation of an artificial anal sphincter in a man with severe anal incontinence an myasthenia gravis is described. The prosthesis used, an "AMS 800' artificial urinary sphincter, gave the patient complete control of defecation. The technique offers the possibility of curing anal incontinence of neuromuscular origin, for which there has been no treatment until know.

Aged↗
PubMed1987

Effect of sham-feeding on glucose tolerance and insulin secretion.

Glucose, 25 g, was infused iv with or without sham-feeding in seven normal males. Sham-feeding improved glucose tolerance, incremental area of blood glucose being 63% (P less than 0.05) of that during iv glucose without sham-feeding. The actual insulin secretion evaluated from the total area under the C-peptide and insulin curves did not differ during iv glucose with or without sham-feeding. These results suggest that the cephalic-vagal reflex improves glucose tolerance during iv glucose, independent of changes in beta-cell function.

Adult↗
PubMed1984

Scleroderma of the colon presenting with acute abdominal symptoms.

A 66-year-old woman with long-standing systemic sclerosis presented with fever, acute abdominal pain and tenderness. She was treated with antibiotics. At laparotomy six weeks later, a narrow, stiff, friable and fibrotic right colon was found with histological features of scleroderma. The acute attack was interpreted as an ischaemic episode of the colon which later healed by fibrosis.

Abdomen, Acute↗