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Biomedical subjects

I N Ross

Publications and source records attributed to I N Ross.

At least 19 recordsLinked to original sources
PubMed2006

35 J broadband femtosecond optical parametric chirped pulse amplification system.

We report on what is believed to be the first large-aperture and high-energy optical parametric chirped pulse amplification system. The system, based on a three-stage amplifier, shows 25% pump-to-signal conversion efficiency and amplification of the full 70 nm width of the seed spectrum. Pulse compression to 84 fs achieved after amplification indicates a potential of 300 TW pulse power for 35 J amplified pulse energy.

Journal Article↗
PubMed1987

Predicting enteric fever without bacteriological culture results.

We used Bayes' theorem to calculate the probability of enteric fever in 260 patients presenting with undiagnosed fever, without recourse to blood or stool culture results. These individuals were divided into 110 patients with enteric fever (63 culture positive, 47 culture negative) and 150 patients with other causes of fever. Comparison of the frequencies of occurrence of 19 clinical and laboratory events, said to be helpful in the diagnosis of enteric fever, in the two groups revealed that only 8 events were significantly more frequent in enteric fever. These were: a positive Widal test at a screening dilution of 1:40; a peak temperature greater than = 39 degrees C; previous treatment for the fever; a white blood cell count less than 9 X 10(6)/litre; a polymorphonuclear leucocyte count less than 3.5 X 10(6)/litre; splenomegaly; fever duration greater than 7 d; and hepatomegaly. When the probability of enteric fever was determined prospectively in 110 patients, using only 6 of these discriminating events, the probability of patients with a positive prediction having enteric fever (diagnostic specificity) was 0.80 (95% confidence interval: 0.68 to 0.91) and the probability of those with a negative prediction not having enteric fever (diagnostic sensitivity) was 0.92 (0.85 to 0.99). Using all 19 events did not alter the diagnostic specificity or diagnostic sensitivity. This study shows that a small number of clinical and laboratory features can objectively discriminate enteric fever from other causes of fever in the majority of patients. Calculating the probability of enteric fever can aid in diagnosis, when culturing for salmonella is either unavailable or is negative.

Bayes Theorem↗
PubMed1987

Reassessment of faecal alpha-1-antitrypsin excretion for use as screening test for intestinal protein loss.

Faecal alpha-1-antitrypsin and 51Cr-albumin losses in 42 patients with either gastrointestinal or hepatic disease were compared. The reference range was derived from measurements in 20 controls without gastrointestinal disease. Alpha-1-antitrypsin excretion was increased in patients with excessive 51Cr-albumin loss, and correlations were found between alpha-1-antitrypsin clearance and 51Cr-albumin excretion. Because of the considerable overlap of faecal alpha-1-antitrypsin excretion between controls and patients, sensitivity and specificity of the test were only 58% and 80%, respectively. This poor reliability could not be explained by sampling error or temporal variations in alpha-1-antitrypsin excretion. These results show that although faecal alpha-1-antitrypsin excretion correlates with 51Cr-albumin excretion when whole groups of patients are studied, its poor sensitivity makes it an unreliable measure of enteric protein loss.

Albumins↗
PubMed1986

Diagnosing enteric fever: a reappraisal.

The diagnostic value of 19 clinical and laboratory events was assessed in 150 enteric fever cases. A logistic regression analysis revealed only 8 predicitive variables for the presence or absence of enteric fever. These were, in order of importance, the white blood cell count, the S. typhi H agglutinin titre, body temperature, the S. typhi O agglutinin titre, the S. paratyphi A H agglutinin titre, the S. paratyphi B H agglutinin titre, age and the fever pattern. This study showed that objective variables like the Widal titres were useful in predicting enteric fever, whilst symptoms such as abdominal pain were unhelpful. Use of all 8 variables to calculate the probability of enteric fever might provide an accurate method of diagnosing or confirming enteric fever when culture results are unavailable or negative.

Adult↗
PubMed1984

Studies of the pH gradient across gastric mucus.

We studied the possibility that gastric mucosa protects itself from luminal acid by maintaining a neutral zone adjacent to the mucosa. In the anaesthetised rat pedicles of gastric fundus mucosa with an intact mucus layer were studied. Using pH sensitive antimony chloride microelectrodes, we demonstrated a maximal pH adjacent to the mucosa of 6.68 when luminal pH was 2 (n = 30). The intramucus pH was compromised when luminal acidity was greater than pH 1.5. Addition of 10 mM aspirin or 5% N-acetyl cysteine to the luminal solution also caused a fall in intramucus pH. Sodium taurocholate (10 mM) caused a physical change in the appearance of the mucus which became brittle and fragmented. The pH within the mucus layer fell as a result of this fragmentation. 16, 16 dimethyl prostaglandin E2 prevented the fall in intramucus pH produced by 20 mM aspirin. Similar results were obtained in specimens of human gastric mucosa removed at gastrectomy. These observations suggest that an alkaline zone is maintained within the mucus layer adjacent to the gastric epithelium which may have an important protective role.

Animals↗
PubMed1983

The effect of cimetidine on immunological parameters in Crohn's disease: a double blind trial.

Thirty-six patients with Crohn's disease were entered into a double-blind trial to assess any beneficial effect that cimetidine might have on immunological and clinical status. Eighteen patients were randomized to receive cimetidine, 1 g orally for 28 days, and the other 18 patients to receive a placebo. There was no alteration in clinical status in the cimetidine-treated group. Although 64% of the patients were anergic, augmentation of skin tests to candida, mumps, tuberculin, streptokinase/streptodornase and trichophyton antigens, was not observed in the cimetidine-treated patients. The patients with Crohn's disease, as a whole had higher absolute numbers of suppressor T-lymphocytes, 0.70 X 10(9)/litre (0.21-2.36, n = 35) compared to control values, 0.5 X 10(9)/litre (0.16-1.55, n = 25) (P less than 0.05). However, there was no significant difference in proportions of suppressor and helper T-lymphocytes, lymphocyte activation and humoral immunity after cimetidine treatment. The lack of any clear modulation of immunity by cimetidine, would be against trying H2 antagonists in a long term clinical trial.

Adult↗
PubMed1983

Studies of the 'mucus-bicarbonate' barrier on rat fundic mucosa: the effects of luminal pH and a stable prostaglandin analogue.

Gastric mucosa may protect itself from acid peptic digestion by maintaining an alkaline barrier zone within the layer of mucus coating its surface. We have measured the pH gradient in the mucous layer in vivo, on the gastric mucosa of anaesthetised rats using antimony chloride micro pH electrodes. The maximum pH recordable adjacent to the epithelium was 7.43 +/- 0.56 (n = 8) when the luminal bathing solution pH was 2. Adjusting the luminal pH to 7.0 caused the maximal pH to rise to 7.88 (range 7.59 to 8.08), a value which is significantly higher than either luminal or reported intraepithelial pH and suggests that active secretion of alkali is involved. Pretreatment with 16-16-dimethyl prostaglandin E2 (20 micrograms subcutaneously) significantly increased the maximal intramucus pH to 7.89 +/- 0.45 (n = 8) when luminal pH was 2 and prevented the fall in intramucus pH induced by luminal aspirin (20 mM). It did not prevent falls in pH provoked by the mucolytic agent n-acetyl cysteine or by a high luminal activity (pH 1.4). These data indicate that an alkaline environment is maintained adjacent to gastric mucosa and that while this is enhanced by prostaglandin it may be compromised by high luminal acid concentrations or by removal of the support provided by mucus. These observations may be relevant to the mechanisms of gastric mucosal protection against acid peptic damage.

16,16-Dimethylprostaglandin E2↗