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Biomedical subjects

N Shepherd

Publications and source records attributed to N Shepherd.

29 records · Page 2Linked to original sources
PubMed1983

Necrotising granulomata in prostatic resection specimens--a sequel to previous operation.

Six cases, in which necrotising granulomata were discovered in transurethral resection specimens of prostate gland, are described. In four of these cases, granulomata of foreign body type were also present. None of the patients had clinical, microbiological or histological evidence of tuberculosis, past or present. All had had at least one previous prostatectomy. The necrotising granulomata had characteristic microscopic appearances. They were almost certainly caused by operative trauma.

Aged↗
PubMed1981

Evidence that the velocity of sarcomere shortening in single frog atrial cardiac cells is load dependent.

Recent experiments using laser diffraction techniques to determine the time course and extent of sarcomere shortening in thin bundles of cardial tissue have given results which suggest that the velocity of sarcomere shortening in cardiac muscle is independent of the developed force (Nassar et al., 1974; Krueger and Pollack, 1975). However, the anatomical complexity of the intact tissue precludes a definite interpretation of the data, since the exact relationship between the force being borne by the total tissue to the force being borne by any observed group of sarcomeres is uncertain. The single frog atrial cell provides a simple cardiac preparation in which the relationship between sarcomere velocity and sarcomere force is well defined, since these cells are only 1-2 myofibrils wide. The purpose of the present investigation was to determine if sarcomere velocity in the single frog atrial cell is dependent on force by measuring the time course of sarcomere shortening in single cells under conditions in which the cell developed markedly different forces. The results presented in this paper give direct evidence that the velocity of sarcomere shortening in the single cardiac cell depends on the force being developed by the sarcomeres. Thus, cardiac sarcomeres have a type of force-velocity relationship, although the exact nature of this relationship could not be determined in these experiments.

Animals↗
PubMed1980

Synthesis and function of ribonucleic acid polymerase and ribosomes in Escherichia coli B/r after a nutritional shift-up.

The syntheses of stable ribosomal ribonucleic acid (RNA) and transfer RNA in bacteria depend on the concentration and activity of RNA polymerase and on the fraction of active RNA polymerase synthesizing stable RNA. These parameters were measured in Escherichia coli B/r after a nutritional shift-up from succinate-minimal to glucose-amino acids medium and were found to change in complex patterns during a 1- to 2-h period after the shift-up before reaching a final steady-state level characteristic for the postshift growth medium. The combined effect of these changes was an immediate, one-step increase in the exponential rate of stable RNA synthesis and thus of ribosome synthesis. This suggests that the distribution of transcribing RNA polymerase over ribosomal and nonribosomal genes and the polymerase activity are continuously adjusted during postshift growth to some growth-limiting reaction whose rate increases exponentially. It is proposed that this reaction is the production of amino-acylated transfer RNA and that is exponentially increasing rate results in part from a gradually increasing concentration of aminoacyl transfer RNA synthetases after a shift-up. This idea was tested and is supported by a computer simulation of a nutritional shift-up.

Bacterial Proteins↗
PubMed1979

Sarcomere length-resting tension relation in single frog atrial cardiac cells.

It generally has been thought that the relatively high resting tension characteristic of cardiac tissue resides in structures (collagen, elastin) external to the individual cardiac cells, but the evidence to support this conclusion has been indirect, since the resting tension of intact single cardiac cells has not been determined previously. The purpose of the present investigation was to determine the resting tension (stress)-sarcomere length relationships of single intact frog atrial cells. For tension determinations, a single cell was attached between two poly-L-lysine coated glass beams; one beam served as a compliant calibrated cantilevered force beam, and length changes were imposed on the cell by movement of the other beam. Coventional bright-field light microscope techniques were used to view the cell, the sarcomere pattern within the cell, and the position of the force beam. The resting tension of the intact cell increased from a value of about 10 nN at a sarcomere length of 2.35 microns to a value of about 130 nN at a sarcomere length of 3.45 microns. Lagrangian and Eulerian resting stress-sarcomere length relationships were computed from the resting tension-sarcomere length relationships. The Lagrangian stress increased from a value of about 0.6 mN/mm2 at a sarcomere length of 2.35 microns to a value of about 7 mN/mm2 at a sarcomere length of 3.45 microns. These values of stress are about 8- to 30-fold less than those previously reported for intact frog atrial tissue and indicate that the resting tension of intact frog atrial preparations resides primarily in structures external to the individual cardiac cell.

Animals↗
PubMed1976

Ameloblastic fibroma: report of case.

A 3-year-old girl had a large, painless, radiolucent lesion that involved the right side of the mandible. The lesion extended from the canine region to the condyle and coronoid process. A microscopic diagnosis of ameloblastoma was made by the hospital pathologist. Because it is unusual to find an ameloblastoma in a 3-year-old child and because the extensive surgical procedure that would be necessary to remove an ameloblastoma of this size, further consultation was required. As a result, the lesion was diagnosed as an ameloblastic fibroma and a more conservative surgical procedure was performed. Sixteen months after surgery, radiographic evidence showed complete resolution of the bony surgical defect, with no evidence of recurrence. This case once again points out the necessity for exact diagnosis of similar histologic lesions that may require a different approach in treatment.

Ameloblastoma↗
PubMedDate not supplied

Photodynamic therapy using 5-aminolaevulinic acid for oesophageal adenocarcinoma associated with Barrett's metaplasia.

Photodynamic therapy (PDT) is a novel technique for local endoscopic treatment of gastrointestinal neoplasia. Current photosensitisers for PDT may cause prolonged skin phototoxicity. 5-Aminolaevulinic acid (ALA), a precursor of the photosensitiser protoporphyrin IX (PpIX), is more acceptable because of its short half-life and preferential accumulation in mucosa and mucosal tumour. We have treated 12 patients, median age 73 years (range 55-88) with oesophageal adenocarcinoma arising from Barrett's metaplasia (two carcinomas-in-situ, grade 0; 10 carcinomas, grade 1-11A based on endoluminal ultrasound in two and CT scanning in 10 patients). ALA (60 and 75 mg/kg body weight) was given orally in two or five equally divided doses. The PpIX distribution in stomach, normal oesophagus, Barrett's mucosa and carcinoma was measured by quantitative fluorescence photometry. PDT was performed using laser light (630 nm) delivered via a cylindrical diffuser 4-6 h after the first dose of ALA. The patients received one to four sessions of PDT. PpIX accumulation in the mucosa was two to three times that in the lamina propria. The differential distribution between carcinomatous and normal oesophageal mucosa was less marked (carcinoma:normal mucosa ratio = 1.4). Higher doses of ALA increased PpIX accumulation in all tissues but did not increase the differential PpIX distribution between tumour and normal oesophageal mucosa. After PDT using ALA (ALA/PDT), all mucosa showed superficial white necrotic changes and the histology confirmed fibrinoid necrosis. One patient with carcinoma-in-situ had the tumour eradicated after one treatment with no recurrence at 28 months. Another patient with a small T1 tumour required four ALA/PDT treatments, and died of other disease after 36 months. There was no evidence of recurrence. The tumour bulk in the other carcinomas was not significantly reduced. ALA/PDT has a potential for the eradication of small tumours but careful patient selection with endoluminal ultrasound is needed when using ALA/PDT to treat oesophageal cancer.

Adenocarcinoma↗
PubMedDate not supplied

Device tracking: user facility responsibilities.

The purpose of FDA's device tracking regulations is to ensure that tracked devices can be traced from the device manufacturing facility to the person who receives the benefit of the device, that is, the patient. Although the manufacturer has the responsibility for establishing and monitoring the tracking program for their devices, the user facility has a key responsibility in assuring its success. The FDA initially identified 21 devices that require tracking and recently added two more to the list. This paper discusses the tracking system and the responsibilities of the manufacturer and the user facility. Information on each of the initial 21 devices to be tracked is presented, including device nomenclature, description, potential health risks, panel classification and regulation number, risk class, ECRI number, and references.

Consumer Product Safety↗