Intrinsic factor antibody tests.

The sensitivity of methods to detect antibodies to intrinsic factor was assessed. Five sera of known antibody content were tested in 31 laboratories and 30 sera from patients with pernicious anaemia were tested in one laboratory. Five non-commercial methods and two kits for type I antibodies and one non-commercial method for types I and II antibodies are in current use. Differences in sensitivity of the non-commercial methods for type I antibodies related more to the antigen: antibody ratio in the test system than to the method itself. A radioimmune assay for types I and II antibodies showed the best sensitivity but that of an enzyme linked immunosorbent assay (ELISA) method was poor.     

Observer variation in the histopathological classification of thymoma: correlation with prognosis.

AIMS--To assess the ability of three histopathologists, experienced in thoracic surgical reporting, consistently to classify thymomas as cortical, medullary, or mixed pattern tumours. METHODS--Three histopathologists classified 74 thymomas (none frank carcinomas) as of either cortical, medullary, or mixed pattern, on two separate occasions. Kappa statistics were used to assess inter- and intra-observer agreement. Tumour type was compared with surgical stage as a predictor of biological behaviour. RESULTS--Inter- and intra-observer agreement were only moderate (kappa 0.48 and 0.52, respectively). For only 26 of 74 tumours could a categorisation be consistently agreed on. Follow up information was obtained for 73 cases, with a mean follow up period of five years. The prognoses for those 26 of 74 cases appeared to be at variance from previously reported studies, and showed internal inconsistency, with the mixed pattern category showing a worse survival than the cortical category. For the group as a whole, however, stage at presentation was related to survival, with an overall five year survival of 78% (100% for stage I, 84% for stage II, 27% for stage III and 0% for stage IV). CONCLUSIONS--The classification of thymomas into cortical, medullary, or mixed pattern tumours is difficult to apply. Surgical stage remains a better guide to prognosis.     

Experiences with dual protein bound aqueous vitamin B12 absorption test in subjects with low serum vitamin B12 concentrations.

A dual isotope vitamin B12 absorption test in which vitamin B12 is given both in aqueous solution and bound to protein (chicken serum), was evaluated in 26 controls and 68 patients with subnormal serum vitamin B12 concentrations (19 with pernicious anaemia, 13 with iron deficiency, seven after partial gastrectomy, seven with malabsorptive states, five with folate deficiency, four with chronic alcoholism and 13 in whom no cause was apparent). In control patients protein bound absorption decreased with age; isotope excretion was 1.0% or over in those aged under 60 and 0.5% or over in those aged 60 and above. Malabsorption of protein bound vitamin B12 with normal aqueous absorption occurred in five patients with iron deficiency, three with alcoholism, two after partial gastrectomy, two with folate deficiency and in one with a malabsorptive state. In alcoholics abstinence produced an improvement in protein bound absorption. All patients in the group for whom no cause could be found for the subnormal serum vitamin B12 concentration had normal aqueous absorption but four had malabsorption of protein bound vitamin. Although the dual isotope test gave reproducible results and was consistent with the standard Schilling test some anomalies were detected; nine patients had reduced aqueous absorption with normal protein bound absorption. Despite this the dual test may prove useful in determining the importance of a subnormal vitamin B12 concentration where the cause is not clinically apparent. Further development is needed before it can be considered for routine use.     

Tip-oriented adherence of Treponema denticola to fibronectin.

The adherence of Treponema denticola to ligands on cell surfaces or in basement membranes of periodontal tissues might play an important role in its pathogenicity. A direct microscopic assay was used to examine the binding of T. denticola to fibronectin and other protein substrates adsorbed on plastic cover slips. All strains of T. denticola that were tested adhered to fibronectin but to different degrees. The strains which bound in high numbers frequently bound by their tips. Type strain ATCC 33520 bound to fibronectin in high numbers (149 +/- 11.3 bacteria per microscopic field), with 60% bound by the tips. Strain e' bound in high numbers (140 +/- 10.2) and had the highest percentage of tip binding (98%); strain e bound in lowest numbers (39 +/- 8.2) and had the lowest percentage of tip binding (15%). Laminin supported binding at a level similar to that of fibronectin, as did fibronectin fragments which contained the cell binding domain peptides, RGDS. Type IV collagen and non-RGDS peptides did not support binding. Binding to fibronectin and laminin was inhibited by the addition of antifibronectin and antilaminin antibodies. By lowering the incubation temperature from 37 to 4 degrees C, the number of cells that attached decreased by 60% and tip binding was reduced by 50%. Pretreatment of the cells with collagen did not affect binding, whereas fibronectin pretreatment enhanced binding by 50% and laminin pretreatment resulted in a decrease of 60%. T. denticola adheres by its tips to fibronectin-coated surfaces, which suggests that fibronectin-specific adhesins cluster at the tips.     

Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype

Inhibitory neurotransmission in the brain is largely mediated by GABA(A) receptors. Potentiation of GABA receptor activation through an allosteric benzodiazepine (BZ) site produces the sedative, anxiolytic, muscle relaxant, anticonvulsant and cognition-impairing effects of clinically used BZs such as diazepam. We created genetically modified mice (alpha1 H101R) with a diazepam-insensitive alpha1 subtype and a selective BZ site ligand, L-838,417, to explore GABA(A) receptor subtypes mediating specific physiological effects. These two complimentary approaches revealed that the alpha1 subtype mediated the sedative, but not the anxiolytic effects of benzodiazepines. This finding suggests ways to improve anxiolytics and to develop drugs for other neurological disorders based on their specificity for GABA(A) receptor subtypes in distinct neuronal circuits.     

Brief intense exercise followed by passive recovery modifies the pattern of fuel use in humans during subsequent sustained intermittent exercise

The role of work period duration as the principal factor influencing carbohydrate metabolism during intermittent exercise has been investigated. Fuel oxidation rates and muscle glycogen and free carnitine content were compared between two protocols of sustained intermittent intense exercise with identical treadmill speed and total work duration. In the first experiment subjects (n=6) completed 40 min of intermittent treadmill running involving a work : recovery cycle of 6 : 9 s or 24 : 36 s on separate days. With 24 : 36 s exercise a higher rate of carbohydrate oxidation approached significance (P=0.057), whilst fat oxidation rate was lower (P ≤ 0.01) and plasma lactate concentration higher (P ≤ 0.01). Muscle glycogen was lower post‐exercise with 24 : 36 s (P ≤ 0.05). Muscle free carnitine decreased (P ≤ 0.05), but there was no difference between protocols. In the second experiment a separate group of subjects (n=5) repeated the intermittent exercise protocols with the addition of a 10‐min bout of intense exercise, followed by 43 ± 5 min passive recovery, prior to sustained (40 min) intermittent exercise. For this experiment the difference in fuel use observed previously between 6 : 9 s and 24 : 36 s was abolished. Carbohydrate and fat oxidation, plasma lactate and muscle glycogen levels were similar in 6 : 9 s and 24 : 36 s. When compared with the first experiment, this result was because of reduced carbohydrate oxidation in 24 : 36 s (P ≤ 0.05). There was no difference, and no change, in muscle free carnitine between protocols. A 10‐min bout of intense exercise, followed by 43 ± 5 min of passive recovery, substantially modifies fuel use during subsequent intermittent intense exercise.     

Improved oocyte quality is obtained with follicle stimulating hormone alone than with follicle stimulating hormone/human menopausal gonadotrophin combination

The aim of this study was to compare the efficacy of pure follicle stimulating hormone (FSH) with that of FSH/human menopausal gonadotrophin (HMG) combination in downregulated cycles. A total of 357 patients was evaluated retrospectively. Sixty percent of patients in the FSH group and 55% in the FSH/HMG group were new; the others were repeat patients. Ovulation was suppressed with leuprolide acetate in all patients, followed by either FSH (n = 218) or FSH/HMG (n = 119). There was no difference in patients' age, infertility factors, number of ampoules used, length of stimulation, oestradiol levels on day of human chorionic gonadotrophin (HCG) administration, number of oocytes recovered or the number of embryos transferred. Also, nuclear maturity at aspiration and fertilization rates were not different between the two groups. FSH stimulation resulted in a significantly higher percentage of mature oocytes that showed the typical 'mature' morphological characteristics (P < 0.0001). The clinical pregnancy rates per transfer were 40 and 28% in patients stimulated with pure FSH and FSH/HMG respectively (P < 0.05). The significantly higher number of immature oocytes matured in vitro in the FSH/HMG group (P = 0.001) suggests a possible effect on in-vitro maturation, due to luteinizing hormone present in HMG. The difference in mature oocyte quality may be an important determinant in the higher pregnancy rates for the FSH- stimulated patients.