Leonard F. Blackwell

Structure and biological activity of nitrogen and oxygen coordinated nicotinic acid complexes of chromium

Abstract A series of N-coordinated M(II)(nic)2(H2O)4≠ complexes, where M = Co, Ni, Mn or Cr and the O-coordinated species Cr(III)(nic)2(H2O)4+ and Cr(III)(nic)(H2O)5+2 have been prepared. A single crystal X-ray analysis of the complex Cr(II)(nic)2(H2O)4 shows that the chromium ion is in the +2 oxidation state and that two nicotinic acid ligands are coordinated in a trans arrangement via the pyridine ring nitrogen atoms. The four equatorial positions are occupied by water molecules. Biological activity measurements with a yeast bioassay system however show that none of the N-coordinated complexes possess any glucose tolerance factor (GTF-type) activity. On the other hand, the O-coordinated chromium(III)-dinicotinic acid complex is biologically active which suggests that a trans arrangement of pyridine nitrogen atoms resembles that part of the GTF structure which is recognised by the receptors or enzymes which are involved in the expression of the biological effect.

Chromium(III) complexes and their relationship to the glucose tolerance factor. Part II. Structure and biological activity of amino acid complexes

Abstract A number of octahedral chromium complexes with amino acids are ligands have been prepared and their structures assigned on the basis of their chromatographic and spectral properties. These include complexes with the general structure Cr(AA) 2 (H 2 O) 2 where the amino acids glycine, glutamic acid and glutamine act as bidentate ligands. The analogous compound with cysteine as ligand is stable at low pH, but at high pH a terdentate cysteine complex, Cr(cysteine) 2 − , is formed. These complexes, as well as a solution of monodentate glycine aquo complexes, and Cr-nicotinic acid-glycine and Cr-nicotinic acid-cysteine complexes of undetermined structure, have been assayed for glucose tolerance factor activity using a yeast assay. Only Cr(glutamine) 2 - (H 2 O) 2 + , Cr-nicotinic acid-glycine and the mixture of complexes Cr(glycine) n (H 2 O) 6-n +3 showed significant activity. It is proposed that a trans arrangement of the non-coordinated nitrogen atoms in the ligands of these complexes can mimic the structural features of the glucose tolerance factor which are essential for biological activity.

Definition of the potentially fertile period from urinary steroid excretion rates. Part II. A threshold value for pregnanediol glucuronide as a marker for the end of the potentially fertile period in the human menstrual cycle

Application of time series analysis to a database containing serial pregnanediol data from 113 complete ovulatory menstrual cycles contributed by 83 women of proven fertility and 68 cycles for which pregnanediol values were available over the ovulatory period, detected the first statistically significant risk in pregnanediol excretion for all cycles for which a baseline was available (n = 170). However, even at the 99% confidence level, for 22% of cycles a rise was observed before the presumed day of ovulation. Therefore, a threshold value for pregnanediol was sought from the database as a better marker for the end of fertility. A value of 1.4 mg per 24 h was not reached before day 2 after the pre-ovulatory estrogen peak day for 96% of the cycles. In the remaining 4% of cycles it was reached one day after the total estrogen peak day. The validity of this threshold was confirmed in extensive studies using the Ovarian Monitor where the equivalent is 6.3 mumol per 24 h of pregnanediol glucuronide and measurements are performed on timed urine specimens with a minimum collection time of three hours. These studies were as follows: 1) a World Health Organization study on the use of the Ovarian Monitor as a fertility self test in the home (108 cycles), 2) a multicenter study on returning fertility during breast feeding conducted by Family Health International (73 women), and 3) the general application of the Ovarian Monitor for pregnancy achievement and avoidance during the past ten years (over 250,000 PdG assays performed in ten countries). With rare exceptions, the use of these threshold values is applicable for all women provided correction is made for urine volume.

The relationship of chromium to the glucose tolerance factor. II

After incubation with CrCl3 X 6H2O (or 51CrCl3 X 6H2O) for 25 days, a sterile growth medium, whole yeast cells harvested after growth on a similar chromium-containing medium for the same period, and the spent growth medium remaining after removal of the yeast were each subjected to the separation procedure reported previously [S. J. Haylock. P. D. Buckley and L. F. Blackwell, J. Inorg. Biochem., in press]. The results obtained showed that most of the eleven chromium-containing fractions isolated previously were artifacts formed as a result of direct reaction between the chromium and components of the medium. An anionic complex (which was the major chromium-containing fraction isolated) was identified as a chromium-glucose complex, but one possessing no biological activity. The biologically active chromium-containing fractions (P-3 and P-4) that were only present after yeast had been grown in the medium were further purified, however, during the purification steps, the biological activity was cleanly separated from the chromium material for both P-3 and P-4. Fraction P-4 was subsequently shown to consist of approximately 90% tyramine, but pure tyramine was not active in the yeast bioassay. Although the structure of the glucose tolerance factor-active component in fraction P-3 could not be determined due to the presence of high concentrations of salt that could not be separated on gel filtration columns, the results show that the glucose tolerance factor from brewers yeast can no longer be regarded as a chromium complex.

Separation of biologically active chromium-containing complexes from yeast extracts and other sources of glucose tolerance factor (GTF) activity

A procedure has been developed, based on ion-exchange chromatography, that readily allows the separation of eleven apparently homogeneous chromium-containing fractions from a brewers yeast extract. Four of the fractions are amphoteric and show no glucose tolerance factor (GTF) activity, three are classified as negative (two of which are biologically inactive, while the third one shows a slight degree of GTF activity), whereas the four cationic chromium-containing fractions all show varying degrees of GTF activity. Application of the separation procedure to other biological sources of GTF activity resulted in a spectrum of cationic fractions, over the pH range 1.75 to 12, which suggests that GTF cannot be a single species. The cationic chromium-containing fraction from pork kidney powder and fraction P-3 from yeast appear to contain the most GTF-active material and P-3 shows saturation kinetics as expected for a biologically significant substance.

Hormonal monitoring of ovarian activity using the Ovarian Monitor, Part I. Validation of home and laboratory results obtained during ovulatory cycles by comparison with radioimmunoassay

A study was conducted to determine the accuracy and reliability of the Home Ovarian Monitor for measuring estrone glucuronide (E1G) and pregnanediol glucuronide (PdG) during ovulatory cycles as a means of monitoring ovarian activity. Approximately 60 ovulating women in three centres collected timed specimens of urine (3h or more) for a total of six cycles each. The women measured the E1G and PdG excretion per 24h in their urine specimens using the Monitor. A local laboratory using the Monitor also measured the excretion. Urine specimens from 18 to 19 cycles were sent frozen to the WHO Reference Laboratory in London where they were analysed for E1G and PdG by the Monitor and by radioimmunoassay (RIA). The correlation coefficients between the Monitor and radioimmunoassay results obtained in London were better than 0.84 in 80% of the cycles. A urine bias caused the Monitor E1G results to be higher than those obtained by radioimmunoassay but the daily patterns were the same. In 50% of the cycles, this bias caused a delay of up to 3 days in identifying the beginning of the E1G rise compared with radioimmunoassay. Timing of the preovulatory E1G peak and the postovulatory PdG rise agreed within the experimental errors of the two systems. The study confirmed that women using the Monitor at home obtained results that were as accurate as those obtained by laboratory procedures. Careful supervision was required to maintain laboratory levels of quality control and interpretation of results.

Application of time-series analysis for the recognition of increases in urinary estrogens as markers for the beginning of the potentially fertile period.

Time-series analysis was applied to the urinary total estrogen data from 142 ovulatory menstrual cycles to determine the first statistically significant increase as a marker for the beginning of the potentially fertile phase. Application of the Triggs tracking signal to each cycle detected an increase in urinary total estrogens above the baseline in every case, with a cumulative probability of > or = 95%. The distribution of first increase days ranged from 10 days before 3.5 days before the presumed day of ovulation with a mean of 6.5 +/- 1.4 days. The significant parameters in the calculation of the tracking signal are the smoothing constant (alpha) which is related to the number of baseline observations, the baseline mean for the cycle, and the variation of the baseline mean. The method allows a calculation of the tracking signal as the cycle unfolds and a statistical assessment can be given each day. The procedure is easily adaptable for computer calculation, and because it is applied to individual cycles avoids the use of population means with the loss of information inherently associated with the combination of data from many cycles. The Triggs tracking signal is an appropriate method of analysis of menstrual cycle data and represents a satisfactory alternative to the more usual cumulative sum procedure. The distribution of the first increases constitutes a reference standard for urinary estrogen assays.

Monitoring of ovarian activity by daily measurement of urinary excretion rates of oestrone glucuronide and pregnanediol glucuronide using the Ovarian Monitor, Part III: Variability of normal menstrual cycle profiles

STUDY QUESTION What are the characteristics of, and how variable are, individual normal menstrual cycle profiles of excretion rates for the urinary metabolites oestrone glucuronide (E1G) and pregnanediol glucuronide (PdG)? SUMMARY ANSWER There is a continuum of menstrual cycle profiles that differ from standard textbook profiles but which can be understood simply in terms of growth, atresia and ovulation of ovarian follicles. WHAT IS KNOWN ALREADY Point-of-care assays with the Ovarian Monitor pre-coated assay tubes, using urine samples diluted to a constant volume per unit time, give laboratory accurate clinical data for individual menstrual cycles. Lay operators can perform the point-of-care assay system at home to achieve reliable and reproducible results, which can be used for natural family planning. STUDY DESIGN, SIZE, DURATION This prospective study involved 62 women, with normal menstrual cycles, recruited from three centres: Palmerston North, New Zealand, Sydney, Australia and Santiago, Chile. The study lasted 3 years. PARTICIPANTS/MATERIALS, SETTING, METHODS Women collected daily urine samples and determined their E1G and PdG rates with a pre-coated enzyme assay system known as the Ovarian Monitor. For two cycles, the assays were repeated in a study centre and the results were averaged to give 113 individual menstrual cycles for analysis. The cycles were displayed individually in a proprietary database program. MAIN RESULTS AND THE ROLE OF CHANCE The individual normal hormonal profiles were more complex than the classic composite curves for 40% of the cycles. Of 113 ostensibly normal cycles, only 91 were potentially fertile and 22 had some luteal phase defect. The oestrone glucuronide and PdG excretion rates were reliable and informative in the non-invasive elucidation of ovulation and ovarian function for both simple and complex profiles. Daily monitoring revealed the variability of normal menstrual cycle profiles. The LH peaks were variable and ambiguous markers for ovulation. LIMITATIONS, REASONS FOR CAUTION The study consisted of cycles only from women with regular cycles of 20-40 days duration. All the women were intending to avoid a pregnancy during the study thus the limits of the fertile window were not tested. WIDER IMPLICATIONS OF THE FINDINGS The principles established in this study should apply to cycles of any length. All peaks in oestrone glucuronide excretion should be tested by concurrent measurements of PdG, which gives a positive indication of the fate of the follicle it represents. The Ovarian Monitor provides a useful addition for practitioners of natural family planning. STUDY FUNDING/COMPETING INTEREST(S) Financial support for this study was obtained from the UNDP/UNFPA/World Bank/WHO Special Programme of Research, Development and Research Training in Human Reproduction (HRP). D.G.C. is currently employed by and holds stock in Manawatu Diagnostics Ltd, a company in the development phase of a potentially competing product. The remaining authors have nothing to declare.

Glucose tolerance factor potentiation of insulin action in adipocytes from rats raised on a torula yeast diet cannot be attributed to a deficiency of chromium or glucose tolerance factor activity in the diet

The nature of the dietary component responsible for adipocytes having the ability to respond to Glucose Tolerance Factor (GTF) was investigated. Rats were raised on either a control diet or one of three diets differing only in the protein source (torula yeast, brewers yeast, or casein). Only in adipocytes from rats fed the torula yeast diet did a GTF fraction prepared from brewers yeast potentiate the action of suboptimal concentrations of insulin in the incorporation of label fromd-[1-14C]-glucose andd-[U-14C]-glucose into CO2 and fatty acids. It was concluded that this potentiation was not the result of a deficiency of GTF activity in torula yeast, because a GTF fraction prepared from torula yeast had similar insulin potentiating activity. Differences in response among diets were not owing to differences in levels of amino acids or owing to concentrations of 22 (Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mo, Na, Ni, P, Pb S, Se, Si, Sn, Sr, Zn) of the 23 trace elements investigated. The level of Mn, was low in all diets, but particularly low in the torula yeast diet. Mn deficiencies have previously been implicated in perturbations of glucose metabolism, so that it is possible that this deficiency may be responsible for the effects attributed to the torula yeast diet.

Validation of a reference ELISA for estrone glucuronide using urine samples normalized by dilution to a constant rate of urine production.

A direct enzyme linked immunosorbent assay (ELISA) system has been optimized as a reference method for the measurement of first statistically significant rises in estrone glucuronide excretion rates in human urine by analysing samples pre-diluted at the time of the collection by the women subjects to a constant urine production rate of 150 mL/h. Validation was achieved by correlation of the individual menstrual cycle profiles with the corresponding estrone glucuronide excretion rates determined by radioimmunoassay (RIA) on the same urine samples for a total of 221 samples from nine cycles. The pre-dilution procedure removed random variations due to fluctuations in the daily rate of urine excretion and minimized between sample matrix effects. When the ELISA data were correlated with the RIA data, Deming regression gave a slope of 1.20+/-0.03 and an intercept of 4.6+/-1.8 nmol/24h (r=0.944) and a random experimental error of 14.2 nmol/24h. The major difference in the measurements was a proportional error of 20%, which was present in either the ELISA or RIA methods or in both. Comparison of the standard normal variate transformation of the ELISA and RIA data gave hormonal profiles of the individual menstrual cycles (N=9) that overlapped almost perfectly. Statistically significant rises or falls in the magnitude of the excretion rate in one profile were mirrored faithfully in the other.