Biomedical subjects

J J Dawson

Publications and source records attributed to J J Dawson.

8 recordsLinked to original sources

PubMed2001

Is in-stream processing an important control on spatial changes in carbon fluxes in headwater catchments?

Data on small-scale spatial variations in instantaneous fluxes and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and free carbon dioxide (CO2) are presented for a small acidic headwater stream in NE Scotland. Chloride is used as a conservative element to estimate additional, diffuse inputs of water into the main stem of the stream, other than those from tributaries. Downstream changes in instantaneous carbon fluxes were calculated and then used to estimate losses and gains of carbon within the stream system. Dissolved organic carbon concentrations in the stream ranged from 1.19-6.06 mg l(-1) at its source to a maximum of 10.0-25.3 mg l(-1) as the stream passed through deep peats; DOC concentrations then declined in the lower part of the catchment. DIC concentrations were initially low, increased to 1.5-3.0 mg l(-1) and then decreased to 0.1-1.65 mg l(-1) at the lowest site. Free CO2 concentrations increased from 0.35 mg l(-1) at the stream source to 3.30 mg l(-1) as the stream passed through the peat dominated area. Continually high inputs of CO2-rich water (> 6.0 mg l(-1)) from tributaries maintained these high concentrations in the main stem, until approximately 1.74 km downstream, when there was a rapid decline in concentration. Significant changes in DOC, DIC and CO2 fluxes occur over a distance of 2.7 km downstream from the stream source to the catchment outlet. Between 5.64-41.5 mg C s(-1) as DOC and 2.52-16.2 mg C s(-1) as DIC are removed from the water column. Between 6.81 and 19.0 mg C s(-1) as CO2 is lost along the stream length as progressive equilibration with the atmosphere occurs. We estimate that 11.6-17.6% of the total DOC flux is removed from streamwater by in-stream processes. Dissolved inorganic carbon (HCO3- and free CO2) losses are in excess of nine times its measured flux at the outlet of the catchment. These results suggest that in-stream processing of DOC and DIC and outgassing of CO2 are important controls on the spatial variability of carbon fluxes within headwater streams in upland catchments dominated by organic-rich soils.

Carbon↗

PubMed1996

A randomized study comparing laparoscopic versus open repair of perforated peptic ulcer using suture or sutureless technique.

OBJECTIVE: This study compares laparoscopic versus open repair and suture versus sutureless repair of perforated duodenal and juxtapyloric ulcers. BACKGROUND DATA: The place of laparoscopic repair of perforated peptic ulcer followed by peritoneal toilet of the peritoneal cavity has been established. Whether repair of the perforated peptic ulcer by the laparoscopic approach is better than conventional open repair and whether sutured repair is better than sutureless repair are both undetermined. METHODS: One hundred three patients were randomly allocated to laparoscopic suture repair, laparoscopic sutureless repair, open suture repair, and open sutureless repair. RESULTS: Laparoscopic repair of perforated peptic ulcer (groups 1 and 2) took significantly longer than open repair (groups 3 and 4; 94.3 +/ 40.3 vs. 53.7 +/ 42.6 minutes: Student's test, p < 0.001), but the amount of analgesic required after laparoscopic repair was significantly less than in open surgery (median 1 dose vs. 3 doses) (Mann-Whitney U test, p = 0.03). There was no significant difference in the four groups of patients in terms of duration of nasogastric aspiration, duration of intravenous drip, total hospital stay, time to resume normal diet, visual analogue scale score for pain in the first 24 hours after surgery, morbidity, reoperation, and mortality rates. CONCLUSIONS: Laparoscopic repair of perforated peptic ulcer is a viable option. Sutureless repair is as safe as suture repair and it takes less time to perform.

Adult↗

PubMed1996

Muscarinic autoinhibition of acetylcholine release in mouse atria is not transduced through cyclic AMP or protein kinase C.

1. The present study investigated the second messenger pathways that may mediate muscarinic receptor autoinhibition of acetylcholine release in mouse atria. The stimulation-induced (S-I) outflow of radioactivity from mouse isolated atria incubated with [3H]-choline was Ca(2+)-dependent and tetrodotoxin-sensitive and was used as an index of neuronal acetylcholine release. 2. The cell permeable analogue of cyclic AMP, 8-bromocyclic AMP (1 x 10(-3)M) enhanced the S-I outflow of radioactivity (33%), lower concentrations having no effect. Similarly, the adenylate cyclase activator forskolin (1 x 10(-5)M) had a small facilitatory effect on acetylcholine release. On the other hand the phosphodiesterase inhibitor 3-isobutylmethylxanthine (1 x 10(-4)M) had no effect on the S-I outflow of radioactivity. Together these results suggest that the adenylate cyclase/cyclic AMP system does not have an appreciable role in the modulation of acetylcholine release. 3. The protein kinase C activator phorbol dibutyrate (0.1-3 x 10(-6)M) enhanced the S-I acetylcholine release (maximally by 45%). The effects of phorbol dibutyrate were attenuated by the protein kinase inhibitor staurosporine (1 x 10(-7)M), which by itself had no effect on the S-I outflow of radioactivity. This latter result suggests that there is no tonic activation of protein kinase C during acetylcholine release. 4. Atropine (1 x 10(-7)M) markedly enhanced (232%) the S-I outflow of radioactivity, presumably by preventing feedback inhibition on acetylcholine release through prejunctional muscarinic receptors. This effect is unlikely to involve adenylate cyclase or protein kinase C since it was far greater than the effects of activation of either system with forskolin and phorbol dibutyrate, respectively. Furthermore, the facilitatory effect of atropine was not attenuated by staurosporine, which although a protein kinase C inhibitor, is also an effective inhibitor of cyclic AMP dependent protein kinase (protein kinase A).

1-Methyl-3-isobutylxanthine↗

PubMed1976

A new humidifier.

A new heated water-bath humidifier operates on a new basic principle which overcomes the practical disadvantages of existing systems. A heated hose is used to control a temperature drop along the whole length of the delivery line instead of raising the temperature of the gases in the delivery line as in previous systems. Therefore the tank does not have to fully saturate the gases and a simple, totally cleanable design is possible. A temperature sensor at the delivery point controls the hose heater, constituting a rapid response, low thermal inertia system and delivery temperature is displayed on the unit. Compensation for varying gas flows and ambient temperature changes is inherent and the unit is suitable for neonatal/paediatric and adult use without special adjustment. The tank has a separate reservoir chamber which feeds an evaporation chamber via a cleanable float valve, conferring many advantages including clearly visible water levels, easy filling without breaking the circuit and constant compression volume. Full fail-safe alarm systems are incorporated.

Adult↗

PubMed1975

Quality of life.

Explore the source record for details and available documents.

Family↗

PubMed1970

Attack rate of tuberculosis in a 5-year period among close family contacts of tuberculous patients under domiciliary treatment with isoniazid plus PAS or isoniazid alone.

This report from the Tuberculosis Chemotherapy Centre, Madras, considers the risk, over a 5-year period, to close family contacts of sputum-positive patients treated at home for 1 year with a standard regimen of isoniazid plus PAS or one of 3 regimens of isoniazid alone. The attack rate of tuberculosis in the contacts did not appear to be influenced by the treatment received by the patients in the first year or by the duration in the 5-year period for which the patients had (1) positive sputum smears, (2) positive cultures, or (3) isoniazid-resistant cultures. Further, over half the cases of tuberculosis developed in the first year, many of these being in the first 3 months. These findings confirm the conclusions reached from an earlier study, namely, that the major risk to the contacts is from exposure to the infectious patient before diagnosis, and that the risks from the other possible sources of infection (the patient during treatment and the urban environment of Madras) are, in comparison, small.

Ambulatory Care↗

PubMed1966

A controlled study of the influence of segregation of tuberculous patients for one year on the attack rate of tuberculosis in a 5-year period in close family contacts in South India.

This report is the last of a series of nine publications from the Tuberculosis Chemotherapy Centre, Madras, concerning various aspects of an investigation of the role of ambulatory chemotherapy for pulmonary tuberculosis. It presents the attack rates of tuberculosis over a 5-year period of follow-up of close family contacts of patients, all of whom were treated for one year with isoniazid plus PAS, half (selected at random) in sanatorium and half at home. The incidence of active tuberculosis and of tuberculous infections was no greater in the contacts of patients treated at home than in the contacts of patients treated in sanatorium, either in the first year or over the subsequent four years. The major risk to the contacts resulted from exposure to the patient before diagnosis. These findings reaffirm that close family contacts of patients treated at home were at no additional risk of developing tuberculosis, provided the patients received effective chemotherapy. Finally, this study has shown that it is possible in South India to obtain extremely good co-operation from a group of families over a period of several years.

Follow-Up Studies↗

PubMed1966

A 5-year study of patients with pulmonary tuberculosis in a concurrent comparison of home and sanatorium treatment for one year with isoniazid plus PAS.

This report from the Tuberculosis Chemotherapy Centre, Madras, summarizes the progress over a 5-year period of 193 patients with newly diagnosed, sputum-positive pulmonary tuberculosis who were admitted to a concurrent comparison of home and sanatorium treatment for one year with isoniazid plus PAS. Previous reports have shown that, despite the traditional advantages of sanatorium treatment-rest, adequate diet, nursing and supervised drug-administration-the home patients responded nearly as well as the sanatorium patients in the first year; further, the relapse rates over a 2-year period of follow-up were similar. The findings in the present report are based on a 4-year period of follow-up and extend these conclusions, the relapse rates over the period being 7% for the home patients and 10% for the sanatorium patients.Patients who failed to respond to treatment in the first year and those who had a bacteriological relapse in the second or subsequent years were usually re-treated with reserve regimens, first with streptomycin plus pyrazinamide and, if this was ineffective, with cycloserine plus ethionamide. Considering the findings over the entire 5-year period, five home patients and three sanatorium patients died from non-tuberculous causes. Of the remainder, 5% of the home patients and 6% of the sanatorium patients died of tuberculosis, 4% in each series had bacteriologically active disease at five years and 90% and 89%, respectively, had bacteriologically quiescent disease at that time. These findings are very encouraging, particularly for developing countries such as India, where tuberculosis is a major problem and sanatorium beds are very few.

Aminosalicylic Acids↗