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Biomedical subjects

N J London

Publications and source records attributed to N J London.

At least 19 recordsLinked to original sources
PubMed1995

Functional studies of rat, porcine, and human pancreatic islets cultured in ten commercially available media.

There have been no extensive studies investigating the effect of tissue culture media on the in vitro functional characteristics of rat, porcine and human Islets of Langerhans. We therefore aimed to compare ten commercially available tissue culture media on the basis of their ability to maintain islet viability. Following isolation, islets were cultured free-floating in the ten media (RPMI 1640-11mM glucose (control), RPMI 1640-2.2mM glucose, Dulbecco's MEM, TCM 199, CMRL 1066, Iscove's MEM, Waymouth's MEM, Serum-Free medium, Ex-cell 300, Ham's F-12) and viability was assessed after 24 hr, 3 days, and 7 days on the basis of macroscopic appearance, cell membrane integrity, and insulin secretion in response to glucose stimulation both by dynamic incubation and by perifusion. Each islet species demonstrated physiological insulin release characteristics in all media--however, it was possible to distinguish between the media by comparing the stimulation indices calculated from the insulin release studies. Significantly higher stimulation indices were produced in Iscove's MEM for rat islets, in Ham's F-12 for porcine islets and in CMRL 1066 for human islets. Over the entire culture period a significant deterioration in function was observed in all species cultured in the control media, although this was reversed when islets were cultured in the optimal media. Furthermore, in the case of porcine and human islets a significant improvement in function over the seven-day period was noted in the optimal media. In conclusion, of the commercially available media, the optimal tissue culture medium for rat islets is Iscove's MEM, for porcine islets is Ham's F-12, and for human islets is CMRL 1066.

Animals↗
PubMed1995

Interpretation of embolic phenomena during carotid endarterectomy.

BACKGROUND AND PURPOSE: Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two. METHODS: We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL. RESULTS: The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase. CONCLUSIONS: This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.

Embolism, Air↗
PubMed1992

Storage of human pancreatic digest in University of Wisconsin solution significantly improves subsequent islet purification.

Density-gradient purification of human pancreatic islets from the collagenase-digested pancreas relies on the exocrine tissue being denser than the islets. Cold storage of the pancreas before and after digestion causes cell swelling, which can decrease the density of pancreatic exocrine tissue and adversely affect subsequent purification. Using 14 human pancreata (seven perfused in situ with hyperosmolar citrate (HOC) and seven with University of Wisconsin solution (UW)), it is shown that storage of the pancreatic digest in UW significantly increases the density of pancreatic exocrine tissue compared with storage in minimal essential medium (MEM) (P = 0.009). This results in an improvement in islet purity (P = 0.036) for HOC- but not UW-perfused pancreata. Storage in UW for 1 h not only prevented the deterioration that occurred in MEM, but resulted in an improvement in islet purity for five of the seven HOC-perfused pancreata. Most pancreata in the UK are perfused with HOC, but storage of the digest in UW results in significantly better islet purity and, when islets cannot be purified immediately, a period of storage will often improve separation and allow islets to be purified.

Adenosine↗
PubMed1992

Relation of diagnostic serum amylase levels to aetiology and severity of acute pancreatitis.

The sensitivity of diagnostic serum amylase (greater than 1000 iu/l) was assessed in 417 patients with acute pancreatitis as a result of gall stones (258), alcohol (104), or miscellaneous causes (55), of whom 111 (27%) had a clinically severe attack (including 34 deaths). On hospital admission, an amylase value diagnostic of pancreatitis was found in 96.1% of all mild cases and in 87.4% of severe cases (p less than 0.001); at 48 hours these values were 33.3% and 48.2% respectively (p = 0.026). Diagnostic amylase levels for alcoholic patients were found in 86% of mild cases on admission and in 76% of severe cases (p less than 0.001, compared with other groups). The diagnostic levels were also significantly lower at 24 hours for both the alcoholic and miscellaneous groups compared with the gall stone group (p less than 0.001). Eight of 27 (30%) patients with a serum amylase activity less than 1000 iu/l had pancreatic necrosis compared with 12 of the remaining 390 (3.1%) patients (p less than 0.001); the mortality was also significantly different (44% v 5.6% respectively, p less than 0.001). These data support the view that more sensitive tests for acute pancreatitis are needed for routine use especially in those whose disease has an alcoholic aetiology.

Acute Disease↗
PubMed1992

Therapeutic options in subclavian artery disease.

Chronic ischaemia of the upper limb secondary to subclavian artery disease is uncommon. These patients may present with a variety of symptoms caused by cerebrovascular or upper limb hypoperfusion. If these symptoms are severe, revascularization may be required. This may be accomplished by percutaneous transluminal angioplasty or surgery. The experience of the management of these patients has been reviewed to document their presentation, treatment and outcome.

Adult↗