Biomedical subjects
Publications and source records attributed to D B Gordon.
A high-performance liquid chromatography protocol has been developed for the analysis of snake venoms. This system has been used to isolate eight fractions from Malayan pit viper (Calloselasma rhodostoma) venom. The fractions have been analysed using electrospray mass spectrometry. A number of major components were found with masses ranging from 13,670 to 22,750 Da.
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A proportion of epithelial lymphocytes in various mammalian species is characterised by cells containing cytoplasmic granules. We have studied the total number of granular lymphocytes within surface and crypt epithelium of jejunal mucosae (per 10(4) micron2 muscularis mucosae) from six groups of subjects, comprising (i) young healthy volunteers (ii) family relatives of known coeliac patients, patients with gastrointestinal disorders associated with either (iii) normal or (iv) "flat" mucosae, and groups of (v) untreated and (vi) treated patients with coeliac disease. There was no difference in the absolute number of gEL between the three control groups with normal mucosal architecture, the proportion of granular to total EL per unit of tissue varying between 30-40%. In untreated coeliac mucosae, there was a significantly increased population of gEL, compared with the same control groups (p less than 0.001): the ratio of granular to total EL approximated 65%, and did not differ from flat-control mucosae in which the proportion of gEL was 55%. On withdrawal of gluten, the absolute number of gEL fell significantly in comparison with the untreated coeliac group (p less than 0.05). To further evaluate the effect of gluten challenge, granular lymphocytes were monitored during a five-day period in groups of treated coeliac patients orally challenged with increasing doses (500-3000 mg) of a peptic-tryptic digest of gluten. A significant rise in the absolute number of granular lymphocytes occurred at 12 h, but without any deterioration in mucosal architecture.
Group A streptococci and enterococci can be differentiated from other streptococci by their ability to cleave L-pyrrolidonyl-beta-napthylamide (PYR). The authors evaluated two pyrrolidonyl aminopeptidase (PYRase) systems--Minitek (BBL Microbiology Systems, Cockeysville, MD) and Identicult-AE (Scott Laboratories, Inc., Fiskeville, RI)--for the presumptive identification of Group A streptococci and enterococci. Eighty-three Group A streptococci, 77 beta-hemolytic non-Group A streptococci, 74 enterococci, 56 nonenterococcal non-beta-hemolytic streptococci, 1 Streptococcus pneumoniae, and 1 Aerococcus were tested. Compared with results obtained with reference methods (bile esculin agar and 6.5% [w/v] sodium chloride for identification of enterococci, and latex agglutination tests by Streptex [Burroughs Wellcome, NC] for grouping of beta-hemolytic streptococci) both the Identicult-AE and MInitek systems were 100% sensitive and specific for identification of both enterococci and Group A beta-hemolytic streptococci. Advantages of the Identicult-AE system compared with Minitek were the use of a smaller inoculum for which subculture was not necessary, incubation at room temperature rather than at 37 degrees C, and lower cost. Both PYRase kits tested, and in particular the Identicult-AE system, were very easy to use and should be considered as rapid, reliable, and cost-effective alternative methods for the presumptive identification of Group A streptococci and enterococci in the clinical laboratory.
Fluorescence polarization immunoassay (F.P.I.A.) has rarely been used to measure components of the renin system. Using an Abbott TDX polarimeter and fluorescein - labelled angiotensin I as a tracer we measured angiotensin I by F.P.I.A. Combining this procedure with a renin incubation step enabled measurement of angiotensinogen in human serum. Using sera from male patients and from pregnant females, a good correlation between radioimmunoassay (R.I.A.) and F.P.I.A. was found. Two procedures were developed; one involving taking samples from the renin incubation mixture, the other involving measurement of generated angiotensin I at intervals without interrupting the renin incubation procedure. F.P.I.A. is less expensive and somewhat simpler than R.I.A. but, with the instrument used, it was less sensitive. An unexpected observation was that human renin increases polarization in solutions containing fluorescein labelled angiotensin I, indicating possible binding of renin to angiotensin I.
Chronic administration of two doses of estradiol benzoate (30 and 46 micrograms/kg/day) reduced the drinking response to acute administration of either isoproterenol (25 micrograms/kg, s.c.), the beta-adrenergic agonist, or angiotensin II (Ang II) (200 micrograms/kg, s.c.). The drinking response to intracerebroventricular administration of Ang II (40 ng/kg), but not carbachol (800 ng/kg), was also attenuated in estrogen-treated rats. An assessment of the Ang II binding in a diencephalic block of tissue from estrogen-treated rats revealed a significant reduction compared to untreated controls. The results suggest, but do not prove, that the reduced drinking response observed in estrogen-treated rats may be related to a reduction in the number of Ang II receptors in the brain.
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The hypothesis that increased plasma-renin tends to lower blood-pressure is proposed. Binding of renin to blood-vessel walls is postulated to have some vasodilator action which would oppose the usual blood-pressure-raising action caused by generation of angiotensin. Many of the effects of saralasin and of converting-enzyme inhibitor on blood-pressure in relation to concentrations of renin in blood plasma and in the kidneys seem to support this hypothesis.
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The effect of nephrectomy and ureteral ligation on the plasma zinc levels of zinc-supplemented and unsupplemented rats was studied. Bilateral nephrectomy, and to a greater extent bilateral ureteral ligation, resulted in a significant lowering of plasma zinc in the unsupplemented rats. Sham operation caused a lesser but significant lowering of plasma zinc which was not different from the effect of unilateral nephrectomy or unilateral ureteral ligation. Adding zinc to the drinking fluid of the bilateral nephrectomized rats raised their plasma zinc levels to that of sham-operated controls, but had no effect on the plasma zinc levels of the bilateral ureteral-ligated rats.
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The plasma of eight different species was subjected to electrophoresis on polyacrylamide gel, and the position of renin substrate was determined. There are considerable differences in the electrophoretic mobility of the renin substrates tested. Sheep substrate shows the slowest migration and mouse substrate the most rapid. The species tested appear to fall into two groups: slow-moving substrates occuring in the plasmas of sheep, cow, pig, and rabbit and fast moving substrates in man, dog, rat, and mouse. In most species only a single peak of renin substrate appeared, but in man and dog a minor peak was often observed in addition to the prominent major one. The classification of human renin substrate as an alpha-2-globulin is questioned.
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