Starch utilization by Bacteroides ovatus isolated from the human large intestine.

Starch supported growth of continuous cultures of Bacteroides ovatus when this carbohydrate provided the sole source of carbon and energy. Inducible amylase and alpha-glucosidase activities were inversely related to dilution rate in starch-limited and starch-excess chemostats over the dilution rate (D) range D = 0.03/h to D =0.20/h, and were partly repressed during growth under conditions of starch-excess. Preparative isoelectric focusing of B. ovatus cytoplasmic extracts indicated the existence of three distinct starch-hydrolyzing enzymes. Incubation of active fractions from the isoelectric focusing cell with maltose and a variety of low-molecular-weight oligosaccharides (maltotriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose) identified a single amylase activity, an enzyme with combined beta-amylase and glucoamylase/alpha-glucosidase properties, and also a possible pullulanase. The ability of B. ovatus to synthesize several starch-hydrolyzing enzymes with different specificities and activities may confer a significant competitive advantage to this organism in the colonic ecosystem.

Determination of dietary fibre as non-starch polysaccharides with gas-liquid chromatographic, high-performance liquid chromatographic or spectrophotometric measurement of constituent sugars.

Methods for the measurement of dietary fibre as non-starch polysaccharides (NSP) are described. A common enzymic removal of starch and acid hydrolysis of the NSP to their constituent sugars are followed by one of three alternative techniques, gas-liquid chromatography, high-performance liquid chromatography or spectrophotometry, for measurement of the released sugars. The results obtained by the three methods are in good agreement for a wide range of raw and processed foods. NSP compose approximately 90% of the plant cell-wall material and are therefore a good index of this material. Values for NSP therefore provide a good marker for a diet rich in fruit, vegetables and high-extraction cereal products associated with health and recommended in dietary guidelines. Values for total, soluble and insoluble NSP may be obtained with any of the end-point techniques, and the detailed information obtained from the chromatographic methods is useful in studies of the relationship between the intakes of various types of NSP and health. The causes of some potential interferences in the spectrophotometric assay, especially from processed foods, have been identified and eliminated. The rapid spectrophotometric version is suitable for food labelling purposes and for quality control, and the changes described have made it more robust.

Determination of the uronic acid constituents of non-starch polysaccharides by high-performance liquid chromatography with pulsed amperometric detection.

A technique is described for measurement of the uronic acid constituents of non-starch polysaccharides (NSP) by high-performance liquid chromatography with pulsed amperometric detection using two sets of hydrolysis conditions. In one set of hydrolysis conditions the uronic acid-containing polymers are hydrolysed by prolonged treatment with sulfuric acid only; in the other, the hydrolysate obtained in the Englyst procedure for the measurement of dietary fibre as NSP is buffered to between pH 3.5 and 4 and the uronic acid-containing polymers present are depolymerized enzymically. The conditions for acid hydrolysis only or acid and enzymic hydrolysis of uronic acid-containing polymers optimized for a range of fruit, vegetable and cereal products. Values obtained for total uronic acids are very similar using either hydrolysis procedure, and are in good agreement with values obtained using the spectrophotometric assay as used in the Englyst procedure.

Determination of dietary fibre as non-starch polysaccharides by gas-liquid chromatography.

An improved method is described for the measurement of total, soluble and insoluble dietary fibre as non-starch polysaccharides (NSP). An established procedure is modified to allow more rapid removal of starch and hydrolysis of NSP. In its present form the procedure is simpler and more robust than those previously published. In the modified method starch is removed enzymically within 50 min and NSP is precipitated with ethanol and then hydrolysed by treatment with sulfuric acid for 2 h. The constituent sugars can in turn be measured by gas-liquid chromatography, high-performance liquid chromatography or more rapidly by colorimetry. The improved procedure described here for the removal of starch and hydrolysis of NSP applies to all three techniques, but only the method for measurement of sugars by gas-liquid chromatography is described here in full.

Severity of premenstrual symptoms in relation to medical/psychiatric problems and life experiences.

The Premenstrual Experience Assessment, a comprehensive questionnaire, was completed by 878 women who were currently having menstrual cycles. Their severity of premenstrual symptoms was studied in relation to demographic variables, gynecological problems, use of medications, psychiatric experience, life stressors, and duration of severity. 14 significant relationships were found. The findings are discussed both in terms of research and clinical practice.

Hypercortisolism in patients with functional hypothalamic-amenorrhea.

Hypercortisolism was found in patients with functional hypothalamic amenorrhea (HA) in preliminary short term studies conducted during the morning hours (0800-1100 h). This observation prompted us to characterize the circadian and pulsatile patterns of serum cortisol and LH levels at 15-min intervals for 24 h in 10 women with functional HA and in 7 normal women during the early follicular phase of their cycles. The mean integrated 24-h serum cortisol levels (area under the curve) were significantly (P less than 0.01) higher in the HA patients than in normal women. The mean cortisol levels in the HA patients were elevated (P less than 0.005) compared to those in the normal women during the daytime hours (0800-1600 h), but not during the evening (1600-2400 h) and sleeping hours (2400-0800 h). This selective hypercortisolism during the waking period of the day was almost entirely related to increased duration and amplitude of secretory episodes (peak area) rather than a change in pulse frequency. The serum cortisol increments in response to a noon meal that occurred in normal women were markedly impaired (P less than 0.01) in the HA patients. Compared with that in the normal women, mean LH pulse frequency was reduced by 30% in the HA patients. The 24-h mean LH levels and mean LH pulse amplitude were not significantly different from those in the normal women. However, among the HA patients there were marked individual differences in LH pulse frequency and amplitude, with prolonged interpulse quiescent periods, indicative of dysfunction of the hypothalamic GnRH pulse generator. We conclude that neuroendocrine activation of the ACTH-adrenal axis and inhibition of the GnRH pulse generator in women are associated with HA. Further, spontaneous resumption of normal cyclicity occurred in the majority (8 of 10) of the HA patients with no medical treatment, suggesting that this syndrome is a reversible hypothalamic disorder of a functional nature.

Estrogen therapy arrests bone loss in elderly women.

Although osteoporosis is an age-related disorder, the accelerated bone loss observed in postmenopausal women may be preventable with early diagnosis and adequate estrogen replacement. In a prospective study, we investigated the effect of oral estrogen replacement using conjugated estrogens (Premarin, 0.625 mg) or micronized 17 beta-estradiol (Estrace, 1 mg) versus no estrogen in sequential single-photon bone density measurements over 3-year intervals in 397 postmenopausal women. Estradiol, 1 mg, and conjugated estrogens, 0.625 mg, were equally effective in regarding bone loss. The rate of bone loss was about the same for estrogen users regardless of age (51 to 80 years) and was approximately one third that of nonusers. Among nonusers a uniform accelerated rate of bone loss of 2.5% per year was noted between 56 and 70 years old, whereas between the ages of 51 and 55 years and after age 70 years, the rate of bone loss was significantly less. Ever users over age 65 years showed continued protection from bone loss as long as estrogen therapy was continued. Previous estrogen users who stopped estrogen after age 65 years lost bone more rapidly than women of similar age who had never taken estrogen. Thus to prevent accelerated bone loss in postmenopausal women, we recommend early and continued hormone replacement for life. Estrogen nonusers should be monitored at regular intervals to minimize accelerated bone loss.

Hormonal dynamics during luteal-follicular transition.

To gain insights into the neuroendocrine basis for the initiation of folliculogenesis, the hormonal dynamics during the period from the late luteal to the early follicular phase of the menstrual cycle (the luteal-follicular transition) were examined. Blood samples were obtained at 2-h intervals for 5 consecutive days in seven women and at 15-min intervals for 8 h on each of 4 consecutive days in five women. The results indicate that the luteolytic process, as reflected by an exponential decline of both serum estradiol and progesterone levels, began at least 64 h before the onset of menses. During estradiol and progesterone withdrawal, there was a selective increase in mean serum FSH levels (P less than 0.001) beginning 24 h before and reaching a peak 24 h after the onset of menses. The frequency of LH pulses increased slightly but not significantly during this period, with a significant rise in mean serum LH levels on the day of menses. Thus, an acute rise in FSH concentrations the day before and in LH concentrations the day after the onset of menses occurs during luteal-follicular transition. The dissociation of FSH and LH secretion observed suggests that additional neuroendocrine events other than changes in pulsatile GnRH secretion may be operative during this period. These findings indicate that the initiation of folliculogenesis for the ensuing cycle occurs during the late luteal phase by a process of selective augmentation in FSH secretion independent of hypothalamic GnRH secretion. This event may ultimately prove to be a manifestation of the action of recently characterized ovarian peptides on FSH secretion.

Pituitary apoplexy. A review.

Pituitary apoplexy, a rare but life-threatening condition, may be highly variable in its clinical appearance and therefore should be considered in any patient with abrupt neurologic deterioration. We reviewed the literature on acute massive pituitary infarction to create an awareness of predisposing factors, the pathophysiologic mechanisms responsible for its heterogeneous manifestations, and possible options for investigation and management. These concepts are reinforced by examining the course and outcome of a rare case of pituitary apoplexy manifesting a full range of neurologic and endocrine abnormalities.

Neuroendocrinology of opioid peptides and their role in the control of gonadotropin and prolactin secretion.

Substantial evidence now exists to indicate that the endogenous hypothalamic opioidergic mechanism(s) represents one of the important controlling systems for release of gonadotropin-releasing hormone. Modulations of frequency and amplitude of the secretory activity of gonadotropin-releasing hormone appears to be mediated through an inhibitory action of endogenous opioids, and the functional coupling of the opioidergic and gonadotropin-releasing hormone systems is an ovarian steroid-dependent event. There is also evidence to implicate suprahypothalamic mechanism(s) that enhance endogenous opioid inhibition of secretion of gonadotropin-releasing hormone. Although exogenous opioid peptides and their synthetic analogs consistently induce the secretion of prolactin, blockade of opioid receptors in humans by naloxone failed to elicit a decrement in the levels of prolactin under a variety of conditions. On the contrary, naloxone induced a remarkable increment in the secretion of prolactin via an increased frequency of pulsatile release which is synchronized with pulses of luteinizing hormone. These observations suggest that a common neuroendocrine mechanism is involved in the opioidergic control of the secretion of both luteinizing hormone and prolactin in women.

Naloxone-induced prolactin secretion in women: evidence against a direct prolactin stimulatory effect of endogenous opioids.

Because both opioids and ovarian steroids influence PRL secretion, the relationship between these inputs to PRL control was investigated. Infusion of the opiate receptor antagonist naloxone (1.6 mg/h for 4-8 h) failed to alter serum PRL levels in hypogonadal women or normal women in the early follicular or late luteal phase. In contrast, a prompt and sustained naloxone-induced release of PRL was found in the late follicular and midluteal phases of the cycle, with maximum increments (mean +/- SE) of 16.9 +/- 5.3 and 9.7 +/- 3.2 ng/ml, respectively. In the luteal phase women, the number of PRL pulses was significantly (P less than 0.001) greater during naloxone than during saline infusion (3.4 vs. 1.6 pulses/8 h), and a positive linear correlation was found between the integrated PRL response to naloxone and the levels of circulating estradiol (r = 0.62) and progesterone (r = 0.95). When serum LH concentrations were determined in the same samples, a significantly (P less than 0.001) greater synchrony of PRL with LH pulses during naloxone infusion (96%) compared to that during saline infusion (36%) was found in the luteal phase women. Thus, naloxone infusion induced an increase in pulsatile PRL release which was synchronized with LH pulses. These findings, not previously reported, suggest that a common neuroendocrine mechanism is involved in the opioidergic control of PRL and LH secretion and that this effect of naloxone is manifested only during high ovarian steroid environments.

Evidence for decreased endogenous dopamine and opioid inhibitory influences on LH secretion in polycystic ovary syndrome.

The inhibitory role of the dopaminergic and opioidergic mechanisms in the control of LH secretion in patients with polycystic ovary syndrome (PCO) was evaluated. The administration of an opiate receptor antagonist, naloxone, of a dopamine receptor antagonist, metoclopramide, or of human synthetic beta h-endorphin, were unable to alter LH secretory activity in patients with PCO. Since identical doses of these antagonists and the opiate agonist have elicited respectively a rise and fall of LH levels in normal cycling women, these findings suggest that an underlying hypothalamic component of defect in endogenous dopamine and opioid control may be responsible for the inappropriate gonadotrophin secretion in this syndrome.

The dopaminergic inhibition of LH secretion during the menstrual cycle.

To assess the potential inhibitory role of hypothalamic dopaminergic input on the LRF-LH system, the gonadotropin response to a dopamine receptor antagonist, metoclopramid (MCP, 10 mg iv bolus) was examined during different phases of the menstrual cycle in 12 women. In addition, the role of dopamine infusion on naloxone (opiate receptor antagonist) induced LH increments was examined. MCP induced an abrupt increase in circulating LH levels in the mid-luteal phases but not in the early and late follicular phase subjects. No significant changes in serum FSH levels were observed. Dopamine, when infused concomitantly with naloxone, completely suppressed the naloxone induced pulsatile increments of LH in mid-luteal subjects. These findings support the contention that an increased dopaminergic inhibition of LRF-LH system occurs during the high estrogen-progesterone phase of the menstrual cycle, and provide preliminary evidence that the inhibitory role of endogenous opioids on LRF release may involve the dopaminergic system.

Postpartum hypogonadotrophinism: evidence for increased opioid inhibition.

To investigate a proposed role for endogenous opioids in the inhibition of LH:RH-gonadotrophin release in the postpartum hypogonadotrophic state, LH and FSH responses to naloxone infusion (1.6 mg/h for 2 h) and to a pulse of LHRH (10 micrograms) were measured in five non breast-feeding women. Sequential studies were made at four intervals during the first 25 d postpartum. LH and FSH responses to naloxone were absent on Day 10 postpartum, but significant increments were observed in all studies performed between Days 13-25 postpartum. The relative increments of FSH and LH during naloxone varied as the puerperium progressed; a 3-fold greater release of FSH than LH was found on Day 13 to 15 while the reverse was observed on Day 25. The intermediate days (17-20) yield an equal response. There was a positive linear correlation between the LH and FSH responses to naloxone infusion and to LHRH. These data suggest that the hypogonadotrophinism of the puerperium is due at least in part to increased opioid inhibition of LHRH secretion.

Estradiol, estrone, and gonadotropin levels after use of vaginal estradiol.

The vaginal absorption of 0.5-mg tablets of micronized estradiol was evaluated in postmenopausal women. In a single-dose study, one hour after insertion, a 5.3-fold rise in mean serum estradiol levels and 1.5-fold rise in mean serum estrone levels were observed. Mean levels of luteinizing hormone and follicle-stimulating hormone were significantly depressed. In a three-week alternate-day regimen, mean serum levels of estradiol were consistently two to three times greater than those of estrone 12 hours after insertion. Vaginal absorption of micronized estradiol tablets into the systemic circulation was found to be rapid and efficient. The vaginal route was acceptable and well tolerated by patients. In addition, the major conversion of estradiol to estrone that follows oral or sublingual administration was reduced. The vagina may be a preferred alternate route for estrogen replacement therapy in selected patients.

The disappearance of opioidergic regulation of gonadotropin secretion in postmenopausal women.

In postmenopausal women, the administration of beta-endorphin in repeated pulses (1-2.5 mg) at 1- to 2-h intervals or constant infusion (1 mg/h) for 3-6 h elicited the prompt release of PRL without concomitant change in LH levels. Infusion of an opiate receptor antagonist, naloxone (1.6 mg/h), for 6-7 h also had no effect on LH levels. Since substantial evidence indicates that endogneous opioid peptides exert an inhibitory role on GnRH-LH secretion and that the functional activity of opiate receptors appears to be ovarian steroid dependent, the present observation suggests that the hypersecretion of gonadotropin in the absence of ovarian steroid feedback may, in part, be causally related to a reduced opioid inhibition of GnRH-LH release.

Pituitary hormone release in response to food ingestion: evidence for neuroendocrine signals from gut to brain.

The synchrony of PRL and cortisol release with feeding is now well established. To delineate further the neuroendocrine mechanisms involved, meal-related pituitary and adrenal cortical activities were investigated in seven normal men in a series of experiments conducted in random sequence at 1-week intervals. Ingestion of a standardized mixed meal elicited a consistent acute release of PRL and cortisol at noon (1200 h), but not at breakfast (0800 h). No measurable changes in other pituitary hormones were observed. The relative magnitudes of PRL and cortisol release in response to lunch were not significantly influenced by a preceding breakfast. These responses appear unrelated to the cephalic or oral phases of food ingestion. However, the composition of the meals was found to be important. Whereas carbohydrate meals had no discernible effects, high protein meals induced a large increase in both PRL and cortisol; high fat meals caused selective release of PRL. Ingestion of L-tyrosine and L-tryptophan induced remarkable increments in serum concentrations of both PRL and cortisol, suggesting that these essential amino acids may be active components of the high protein meal. Choline had no effect. Meal-mediated PRL and cortisol release was unaffected by prior receptor blockade of the opioidergic and cholinergic systems with naloxone and atropine, respectively. These observations indicate that the protein component of the meal was responsible for the midday surges of PRL and cortisol and that the cephalic-vagal pathway was not required in food-entrained pituitary hormone release. Further, our data suggest that the neurotransmitter substrates in the protein meal may serve to link the gut and brain by modifying central catecholamine and serotonin biosynthesis, and thereby influence the hypothalamic factors controlling pituitary PRL and ACTH secretion. The possibility that gastrointestinal hormones may also influence the hypothalamic-pituitary system remains to be explored.