Inhibition of microtubule sliding by Ni2+ and Cd2+: evidence for a differential response of certain microtubule pairs within the bovine sperm axoneme

Bovine sperm, extracted with 0.1% Triton X-100, frozen at -20 degrees C for 48-120 hours, and thawed, disintegrated by microtubule sliding when 1 mM MgATP was added. Microtubules and outer dense fibers (ODFs) were usually extruded in groups or "bundles". A total of 44.5% of the cells extruded two distinct bundles, one from each side of the connecting piece, exhibiting opposite curvatures. Only one bundle was observed in 46.2% of the cells, and 9.2% showed no signs of sliding. Transmission electron microscopy (T.E.M.) showed one group consisting of the 4,5-6,7 elements, with the 9,1,2 elements on the other side of the axoneme making up the other bundle. T.E.M. revealed that when only one side of the axoneme had extruded elements, they were always from the 4,5-6,7 group. The remainder of the axoneme (8,9,1,2,3 and the central pair) was left relatively intact, suggesting a difference in the sliding response of the nine pairs of axonemal microtubules. These results indicate a predisposition for sliding between elements 7 and 8 over that between doublets 2 and 3, perhaps due to a disparity in activation thresholds. Also, both Ni2+ and Cd2+ appear to selectively block activation of 2-3 interdoublet sliding. Incubation with 0.25 mM Ni2+ prior to adding MgATP modified the percentages of sliding patterns: 8.6% demonstrated two-sided extrusion, 58.2% showed one-sided, and 33.2% had no extruded bundles. Again, when half the axoneme was missing, it was always the 4,5-6,7 group. Ten micromolar Cd2+ altered the sliding pattern similarly to Ni2+, with 28% two-sided extrusion, 55.9% one-sided extrusion and 16.1% with no extruded bundles. Either pretreatment regimen impeded extrusion of the 9,1,2 group in a high percentage of cells, compared to untreated cells. This specific inhibition of the 9,1,2 side by Ni2+ or Cd2+ is especially significant since Ni2+ also inhibits spontaneous wave initiation in bull sperm (Lindemann et al.: Journal of Cell Biology 87:420-426, 1980), and both Ni2+ and Cd2+ reportedly block the flagellar Ca(2+)-response in rat sperm (Lindemann and Goltz: Cell Motility and the Cytoskeleton 10:420-431, 1988; Lindemann et al.: Cell Motility and the Cytoskeleton 20:316-324, 1991).

Genomic structure of the human prion protein gene

Creutzfeld-Jacob disease and Gerstmann-Sträussler syndrome are rare degenerative disorders of the nervous system which have been genetically linked to the prion protein (PrP) gene. The PrP gene encodes a host glycoprotein of unknown function and is located on the short arm of chromosome 20, a region with few known genes or anonymous markers. The complete structure of the PrP gene in man has not been determined despite considerable interest in its relationship to these unusual disorders. We have determined that the human PrP gene has the same simple genomic structure seen in the hamster gene and consists of two exons and a single intron. In contrast to the hamster PrP gene the human gene appears to have a single major transcriptional start site. The region immediately 5' of the transcriptional start site of the human PrP gene demonstrates the GC-rich features commonly seen in housekeeping genes. Curiously, the genomic clone we have isolated contains a 24-bp deletion that removes one of five octameric peptide repeats predicted to form a B-pleated sheet in this region of the PrP. We have also identified 5' of the PrP gene an RFLP which has a high degree of heterozygosity and which should serve as a useful marker for the pter-12 region of human chromosome 20.

Early detection of acute myocardial infarction: additional diagnostic information from serum concentrations of myoglobin in patients without ST elevation

The value of the 12 lead electrocardiogram, serum total creatine kinase, creatine kinase MB isoenzyme, and myoglobin for the early detection of infarction was evaluated within one hour of admission to the coronary care unit in 82 consecutive patients with suspected myocardial infarction. The 51 patients in whom infarction was diagnosed during the first 24 hours after admission had a higher prevalence of ST elevation (64% v 11%), higher median serum myoglobin (136 micrograms/l v 34 micrograms/l), higher serum creatine kinase (77 IU/l v 34 IU/l), and higher MB isoenzyme (7 IU/l v 4 IU/l) than those in whom it was not. Stepwise logistic regression analysis in 70 patients in whom the electrocardiogram and serum myoglobin were suitable for analysis showed that serum myoglobin was the variable most closely associated with infarction, and contributed additional diagnostic information when ST elevation was entered into the model first. Serum myoglobin remained associated with myocardial infarction when patients who had had symptoms for less than six hours were analysed. An algorithm based on a rapid agglutination test for myoglobin and ST elevation on the electrocardiogram gave an accurate diagnosis in 82% of patients. This approach gave early and rapid recognition of acute myocardial infarction and warrants further examination.

An enzyme-linked immunosorbent assay (ELISA) for the measurement of serum antibodies to growth hormone. The Wessex Growth Study

A solid-phase enzyme-linked immunosorbent assay for measuring antibodies to growth hormone (GH) was developed, with occasional use and long shelf-life in mind. With coating protein concentration optimised, the standard curve was linear over a 25-fold range of concentration. The interassay coefficient of variation ranged from 14.4% to 9.3%. The specificity of the assay was confirmed by the substitution of insulin for GH as coating protein and by preabsorption of sera with GH coupled covalently to Sepharose beads. There was no binding signal with insulin and absorption was dose dependent, maximum (greater than 80% complete) with 2 x 10(4) micrograms GH/ml undiluted serum. The assay was simple to perform, cheap and reliable.

Delivery following cesarean section and perinatal mortality

The perinatal mortality in 1498 patients with one or more previous cesarean section scars delivered between 1972 and 1982 was analyzed. Repeat elective cesarean section was performed in 654 (44%) patients and 844 (56%) were subjected to a "trial of scar." Successful vaginal delivery occurred in 702 (83%) patients and 142 (17%) had emergency repeat operations. There were 46 perinatal deaths, giving a perinatal mortality rate (PMR) of 30.3/1000. It was lowest in patients who electively had a cesarean section (10.6/1000). The corrected PMR was twice as high in the trial of scar group. The PMR for the overall hospital population (27,072 babies) during the study period was 22.5/1000. There were four perinatal deaths in association with dehiscence of the uterine scar. The PMR in trial of scar patients decreased from 40/1000 to less than 20/1000 without a major change in policy. Meanwhile the unit cesarean section rate increased from 5 to 10%, but the repeat section rate was consistent at around 38.5%. Regional analgesia was used in 192 patients, for repeat section in five and trial of scar in 187. Oxytocin was given to 546 (65%) patients. Scar rupture is considered the major contraindication to a trial of scar, but emphasis was not laid on the possible increased perinatal mortality with this procedure before the 1980s. In view of the improvement in the PMR and the added risk to the mother with cesarean delivery, we advocate a policy of trial of scar with informed consent in selected cases.

Studies in human lactation: milk volumes in lactating women during the onset of lactation and full lactation

After validation of test-weighing procedures milk volumes produced by 13 multiparous Caucasian women were followed longitudinally through the first year of lactation. All practiced exclusive breast-feeding for at least 5 mo. Milk transfer to the infant was low on days 1 and 2 and increased rapidly to 498 +/- 129 g/d (means +/- SD) on day 5 and then more slowly to 753 +/- 89 g/d during months 3-5. There was a characteristic milk volume for each mother-infant pair that was significantly related neither to milk yield on days 4-6 nor to birth weight. It was, however, strongly related to infant weight at 1 mo, suggesting that infant and/or maternal factors coming into play during the first month of life are strong determinants of subsequent milk transfer to the infant.

Insulin autoantibodies and insulin assay

Insulin antibodies are known to interfere with the radioimmunoassay of insulin. We tested intravenous glucose tolerance on 25 insulin autoantibody-positive (IAA+) patients and 25 IAA- controls, who were matched for sex, age, and body mass index, to establish if IAA could also interfere with insulin assay. Insulin content was measured in untreated serum, serum precipitated with polyethylene glycol (PEG, free insulin), and serum extracted with acid and precipitated with PEG (total insulin). The mean untreated first-phase insulin response (I1 + 3) for IAA+ patients was 172 +/- 67.3 mU/L, significantly higher than the mean control value of 108 +/- 47.5 (P less than .001). After PEG precipitation, mean I1 + 3 in the patient group fell significantly to 105 +/- 48.4 mU/L (P less than .001), but the control value was unchanged (104 +/- 45.5). The mean percentage fall after PEG precipitation was 36.9% (patients) and 2.9% (controls) (t = 8.3, P less than .001). There was a strong correlation between the IAA titer and the interference in the insulin assay (r = .81). After total insulin extraction of IAA samples, there was a significant fall in mean I1 + 3 to 134 +/- 55.4 mU/L (P less than .001), but the control value was unchanged. IAA can significantly falsify insulin measurement, and care must be taken in the interpretation of insulin-release tests when IAA is present.

Insulin autoantibody polymorphisms with greater discrimination for diabetes in humans

Insulin autoantibodies, like islet cell antibodies, are found not only in the sera of newly diagnosed Type 1 (insulin-dependent) diabetic patients and their relatives, but also in patients with other autoimmunities who do not develop diabetes. Insulin autoantibodies are oligo/monoclonal and frequently binding-site restricted. As determinant selection is genetically determined, we questioned whether certain polymorphisms of insulin autoantibodies, identified by their binding site on the insulin molecule, could better discriminate for Type 1 diabetes, which is also HLA determined. First, we raised monoclonal antibodies to human insulin by classic fusion methods in order to determine the range of antibody polymorphism, and identified five distinct types by their binding profiles to a panel of insulin variants, using an enzyme-linked immunosorbent assay. Two of these polymorphisms, type A and type B, were subsequently found in insulin autoantibody positive human sera using the same panel of insulin variants, and successfully distinguished diabetes-related from diabetes-unrelated individuals. Thus, the type B polymorphism was responsible for binding in 60% of 41 insulin autoantibody positive individuals with polyautoimmune disease but no personal or family history of diabetes (diabetes unrelated), but in only 2% of a group which comprised 17 newly-diagnosed insulin autoantibody positive Type 1 diabetic patients, 19 insulin autoantibody positive discordant twins of Type 1 diabetes and six insulin autoantibody positive healthy siblings of Type 1 diabetic patients (diabetes related) (p less than 0.01). Isolation of the type A polymorphism alone reduced the proportion of false negatives in the insulin autoantibody test for diabetes relatedness from 49% to 20% without diminishing its specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

On the relationship between islet cell antibodies and insulin autoantibodies in patients at risk from insulin dependent diabetes

The frequencies of islet cell antibodies (ICA) and insulin autoantibodies (IAA) were studied in three clinically well defined groups, using an aprotinin sensitised indirect immunofluorescence assay for ICA and a direct binding solid ELISA for IAA, and the association of these two serological markers for insulin dependent diabetes analysed. Frequency of ICA was 10.7% in siblings of diabetics, 15.5% in discordant identical twins and 65.9% in newly diagnosed diabetic patients. Frequency of IAA was 7.1% in siblings, 46.7% in discordant twins and 38.6% in newly diagnosed diabetic patients. No correlation was demonstrated between the two autoantibodies in the siblings. In the newly diagnosed diabetic patients there were sera positive or negative for both, but 22 (50%) of the sera showed dissociation between the two antibodies. The studies of twins showed that IAA and ICA fluctuated independently with time, and demonstrate the inappropriateness of seeking such an association in cross-sectional surveys. An association could not be demonstrated in this group even if data from multiple samples taken at different points in time were pooled, scoring an individual as positive if at any time their sera had been positive for the corresponding antibody. Thus our data showed no correlation between ICA and IAA in any of the groups studied.

Value of insulin autoantibodies as serum markers for insulin-dependent diabetes mellitus

Insulin autoantibodies (IAA) were studied in newly diagnosed insulin-dependent diabetics before the start of insulin treatment and in unaffected identical twins of insulin-dependent diabetics. In 15 of the 40 (38%) diabetics and 27 of the 58 (47%) twins IAA levels exceeded those of 100 controls. Frequency of IAA in unaffected twins was not related to duration of diabetes in their affected twin. In 11 unaffected twins, IAA levels differed in two samples taken 1-12 years apart; IAA were detected at least once in all twins and in one on both occasions. IAA in the twins were not related to the presence of islet-cell antibodies or to HLA-DR 3 or 4. As the unaffected twins of longstanding diabetics are unlikely to develop diabetes, these observations suggest that IAA do not always presage diabetes and are probably not a consequence of the disease; they may reflect an inherited autoimmune tendency to diabetes.

A micro enzyme-linked immunosorbent assay for insulin antibodies in serum

A solid-phase micro enzyme-linked immunosorbent assay for the measurement of insulin antibodies in serum is described and its performance compared with that of an established radiobinding assay. Interassay precision in the ELISA was 10% or less at widely spaced points on the dilution curves for human, porcine and bovine insulins. Specificity was demonstrated by substituting purified human gamma-globulin for the test serum and glucagon for the insulin. The influence on ELISA of endogenous insulin in the test serum was examined by measuring antibody binding before and after extraction of the insulin. The correlation between results from extracted and unextracted sera was 0.96 and the fit ideal: y = 1.00x + 0.38%. The correlation between the results of measuring insulin antibody in 256 diabetic sera by the 2 assays was r = 0.74, P less than 0.001 (human insulin) and r = 0.71, P less than 0.001 (porcine insulin). ELISA is cheap and simple to perform. We believe it may prove to be a practical alternative to radioassay in both the routine detection and investigative research of insulin antibodies.

The distribution of immunoglobulin-containing cells in human autoimmune thyroiditis

The peroxidase-antiperoxidase (PAP) staining method was used to identify immunoglobulin-containing cells in the lymphoid infiltrates of thyroids removed from patients with Hashimoto's autoimmune thyroiditis. A composite picture of the distribution of such cells in the thyroid infiltrate was obtained by carefully superimposing cell-distribution maps from serial histological sections, each stained for a different immunoglobulin class. Ig-containing cells were present to varying extents in all areas of the gland, but were most dense in areas of epithelial 'invasion'. IgG was the commonest immunoglobulin, but there were more cells containing IgD and IgE than IgA or IgM. Both lambda and K light chains were identified in cells occupying the follicle centres. Lymphoid follicle structure was strikingly similar to that described previously for gut-associated lymphoid tissue (GALT), and the theory is advanced that autoimmune thyroiditis represents a form of ectopic GALT in which B-cells, which normally home on markers in the gut, are attracted instead to antigenically active sites in the thyroid.

Metformin kinetics in healthy subjects and in patients with diabetes mellitus

1 The kinetics of metformin were studied after i.v. and oral administration in four healthy subjects and after oral administration in twelve maturity onset (Type II) diabetic patients.

2 After i.v. administration most of the dose was rapidly eliminated but with a mean `terminal' T_1/2 of 4 h measured up to 12 h in plasma and of 16 h measured up to 60 h from the urinary excretion rate. On average, 80% of the dose was recovered as unchanged drug in the urine with none detected in the faeces.

3 After single oral doses (0.5 and 1.5 g), maximum plasma concentrations and urinary excretion rates were observed at about 2 h with urinary recoveries of unchanged drug of 35-50% and faecal recoveries of about 30%. Urinary recoveries were significantly lower after the higher dose. Absolute oral bioavailability was 50-60% of the dose.

4 Deconvolution analysis showed that after a short lag-time, the available oral dose was absorbed at an exponential rate over about 6 h. Implications for the design of prolonged release dosage forms are discussed.

5 Plasma metformin concentrations measured throughout the seventh and fourteenth days of continuous 0.5 g twice daily treatment were accurately predicted from single dose data, although a discrepancy between observed and predicted trough levels reflected the existence of a slow elimination phase. Implications of the latter for a gradual accumulation of metformin in peripheral tissues and a possible association with lactic acidosis are discussed.

6 Renal clearance of metformin was highly correlated with creatinine clearance. However, a weaker relationship between total oral clearance of the drug and creatinine clearance suggests that the latter may not always be a reliable indicator of potential metformin accumulation owing to variability in absorption and possibly non-renal clearance of the drug,