A comparison of in vivo and in vitro methods for determining availability of iron from meals

A comparison is made between in vitro and human and rat in vivo methods for estimating food iron availability. Complex meals formulated to replicate meals used by Cook and Monsen (Am J Clin Nutr 1976;29:859) in human iron availability trials were used in the comparison. The meals were prepared by substituting pork, fish, cheese, egg, liver, or chicken for beef in two basic test meals and were evaluated for iron availability using in vitro and rat in vivo methods. When the criterion for comparison was the ability to show statistically significant differences between iron availability in the various meals, there was substantial agreement between the in vitro and human in vivo methods. There was less agreement between the human in vivo and the rat in vivo and between the in vivo and the rat in vivo and between the in vitro and the rat in vivo methods. Correlation analysis indicated significant agreement between in vitro and human in vivo methods. Correlation between the rat in vivo and human in vivo methods were also significant but correlations between the in vitro and rat in vivo methods were less significant and, in some cases, not significant. The comparison supports the contention that the in vitro method allows a rapid, inexpensive, and accurate estimation of nonheme iron availability in complex meals.     

Plasma lipids, lipoproteins, and triglyceride turnover in eu- and hypo-thyroid rats and rats on a hypocaloric diet

Lipid and lipoprotein concentration, and triglyceride turnover were studied in control, thyroidectomized, and pair-fed control rats (pair-fed to match the food intake of the thyroidectomized rats). Thyroidectomy induced a significant increase in plasma cholesterol (and low density lipoprotein) concentrations and a decrease in plasma triglyceride (and very low density lipoprotein) concentrations. Changes in similar direction but of smaller magnitude were observed in the plasma of the pair-fed control rats. To further investigate triglyceride metabolism in these three groups of animals, triglyceride turnover was studied in fasted, unrestrained, and unanesthetized rats, following injection of [2-3H]glycerol. Peak incorporation of [2-3H]glycerol into plasma triglyceride occurred in all three groups of animals at 25 min after precursor administration, although the maximal incorporation was substantially lower in the thyroidectomized group than in either of the control groups. Thereafter, plasma triglyceride radioactivity decayed monoexponentially with a half-life of 24 +/- 1 min for both normal and pair-fed control rats, compared with the half-life of 41 +/- 3 min observed in the thyroidectomized rats. The calculated apparent fractional catabolic rates were thus 0.029 min-1 for both control groups and only 0.017 min-1 for the thyroidectomized animals. The apparent total catabolic rates of plasma triglyceride were 299 +/- 11, 138 +/- 11, and 48 +/- 4 micrograms triglyceride . min-1 for the normal controls, pair-fed controls, and thyroidectomized rats, respectively. These data further emphasize the importance of thyroid hormones in regulating plasma lipid and lipoprotein metabolism and, specifically, indicate that hypothyroidism results in a reduction of triglyceride secretion into, and the removal from, circulation. Furthermore, evidence was presented that the decreased caloric intake of the hypothyroid animals cannot, in itself, account for this observation.     

The effects of insulin on 3 beta-hydroxysteroid dehydrogenase expression in human luteinized granulosa cells

OBJECTIVE: We determined the relative effects of insulin and FSH on progesterone accumulation as well as activity, protein content, and mRNA expression of 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in human luteinized granulosa cells. METHODS: Luteinized granulosa cells obtained from women undergoing in vitro fertilization were plated and grown to near confluence and treated with FSH, insulin, or a combination of insulin and FSH. Progesterone production as well as enzyme activity, protein content, and mRNA expression for 3 beta HSD were evaluated. RESULTS: Progesterone production was not affected by insulin alone but increased threefold in the presence of FSH (50 ng/microL) alone. The presence of FSH plus insulin (100 nmol/L) caused a significant increase in progesterone accumulation greater than that of FSH alone. The already high basal levels of 3 beta HSD activity were unaffected by insulin alone but increased 1.7-fold in the presence of FSH. The combination of FSH (50 ng/mL) and insulin (100 nmol/L) increased activity 1.3-fold over FSH alone (P < .02). Insulin (greater than 100 nmol/L) alone increased 3 beta HSD protein content as measured by Western analysis 1.8-2-fold over basal levels, whereas FSH alone increased protein content 2.8-fold, and was further augmented by the addition of insulin in a dose-related fashion up to 3.5-fold over basal levels. Insulin increased 3 beta HSD mRNA twofold over basal levels; FSH alone increased mRNA expression of 3 beta HSD 3.2-fold. In the presence of insulin plus FSH, 3 beta HSD mRNA expression increased 7.6-fold over basal levels. For comparison, insulin also stimulated cytochrome P450 aromatase activity, P450 aromatase protein, and mRNA but to a greater degree than that seen for 3 beta HSD. CONCLUSION: Insulin is a regulator of both 3 beta HSD and aromatase expression in human granulosa cells. Elevated insulin levels could therefore affect steroid production in human granulosa cells and presumably alter the menstrual cycle and fertility.     

Evidence that the modulation of membrane-associated protein kinase C activity by an endogenous inhibitor plays a role in N1E-115 murine neuroblastoma cell differentiation

Murine neuroblastoma cells, N1E-115, were induced to differentiate into neuron-like cells by serum deprivation for 18 h. As previous studies have shown that the suppression of protein kinase C (PKC) activity by selective inhibitors or neutralizing antibodies induces neuroblastoma cells to differentiate, we tested the hypothesis that serum deprivation may cause a rapid loss in membrane PKC activity that occurs well before the morphological changes that are characteristic of cell differentiation. A significant reduction in particulate (membrane) PKC activity was indeed observed within 3 h of serum withdrawal when enzyme activity was measured in intact native membranes by the recently described in vitro "direct" assay. This rapid reduction in enzyme activity was confirmed by the decreased phosphorylation of the MARCKS protein, an endogenous PKC-selective substrate, in intact cells. The decrease in membrane PKC activity occurred without any loss in the amount of membrane-associated enzyme, suggesting that some factor(s) resident in neuroblastoma membranes was suppressing PKC activity. Indeed, results indicate the presence of an endogenous inhibitor of PKC tightly associated with neuroblastoma membranes. This inhibitory activity increased in the membranes of cells subjected to serum deprivation, raising the possibility that it was likely responsible for the decline in membrane PKC activity in differentiating N1E-115 cells. Preliminary characterization indicated that the inhibitory activity is a protein and is localized mainly in the membrane fraction. Thus, these results demonstrate directly that endogenous inhibitor can regulate membrane-associated PKC activity in cells and thereby modulate PKC-related neuronal functions.     

Human immune responses to influenza virus vaccines administered by systemic or mucosal routes

Healthy adult volunteers were immunized by parenteral or oral routes with trivalent inactivated influenza vaccine (A/Chile/1/83 (H1N1), A/Mississippi/1/85 (H3N2), and B/Ann Arbor/1/86), or intranasally with live attenuated, cold-adapted influenza type A/Texas/1/85 (H1N1) reassortant virus. In all volunteers, cells spontaneously secreting IgA, IgG or IgM antibodies specific to influenza virus were detected in peripheral blood on days 6-13 after immunization, and specific IgA, IgG and IgM antibodies to influenza vaccine were measured in sera and external secretions (saliva and nasal lavage). Following systemic immunization, a raise in specific antibodies of all isotypes was observed in sera beginning on day 13. Although small variations in IgA and IgM antibodies in saliva and nasal lavages were detected, antigen-specific IgG significantly increased between days 13 and 27. Intranasal administration of attenuated virus induced IgA and IgG antibodies in serum as well as in secretions. Serum antibodies were not substantially influenced by oral immunization, only a small increase in all isotypes was observed in volunteers' sera 21 days after ingestion of vaccine. However, in secretions, antigen-specific IgA and IgG responses were detected one week after immunization and reached a peak response on day 20. These studies show that different routes of immunization can be effective for the induction of specific antibodies, and support the concept of the common mucosal immune system in humans by demonstrating that the oral or intranasal administration of antigen-induced specific antibodies of IgA isotype in external secretions, preceded by the transient appearance in peripheral blood of specific antibody-producing cells.     

Methcathione ("cat"): an enantiomeric potency comparison

With regard to its chemical structure, methcathinone is to cathinone what methamphetamine is to amphetamine. Although it is a drug of abuse outside the United States, methcathione is only recently making an appearance on the clandestine market in this country and has just been classified a Schedule I substance under the Emergency Scheduling Act. We have previously demonstrated that racemic methcathinone produces locomotor stimulation in mice, and substitutes for cocaine and (+)amphetamine in rats trained to discriminate either cocaine or (+)amphetamine, respectively, from saline in tests of stimulus generalization. Because an enantiomeric potency comparison has never been reported for the optical isomers of methcathinone, in the present investigation we synthesized samples of S(-)- and R(+)methcathinone and compared them for their ability: a) to produce locomotor stimulation in mice, b) to elicit cocaine-like responding in rats trained to discriminate 8.0 mg/kg of cocaine from saline vehicle, and c) to elicit (+)-amphetamine-appropriate responding in rats trained to discriminate 1.0 mg/kg of (+)amphetamine from saline vehicle. S(-)Methcathinone was about twice as potent as S(+)amphetamine and three to five times more potent than R(+)methcathinone in the three pharmacologic assays. We conclude that both optical isomers possess central stimulant character, but that S(-)methcathinone is somewhat more potent than R(+)methcathinone.     

Humeral epicondylitis among gas- and waterworks employees

OBJECTIVES: In this cross-sectional study 290 male employees of the public gas- and waterworks of Hamburg, Germany, were examined for symptoms of epicondylitis. Forty-one workers were diagnosed with symptoms of lateral or medial epicondylitis. The effect of employment in different job categories on the prevalence of epicondylitis was explored. METHODS: The diagnosis of epicondylitis was based on the study's own criteria and compared with criteria used in former studies. Jobs were categorized into high, moderate, and no exposure groups according to tasks regarded as strenuous for the elbow. The data were analyzed with the help of multivariate logistic regression. RESULTS: With the study's diagnostic criteria, the prevalence odds ratio (OR) for 10 years of high exposure to elbow straining work was 1.7 [95% confidence interval (95% CI) 1.04-2.68] for currently held jobs and 2.16 (95% CI 1.08-4.32) for formerly held jobs. For workers regarded as moderately exposed in current jobs the odds ratio for 10 years was 1.4 (95% CI 1.00-1.93). Very similar results were obtained for current exposure when stricter diagnostic criteria were employed. CONCLUSIONS: The results suggest a cumulative exposure effect with length of employment. Workers with high exposure in former jobs compared with employees with high exposure in their current job exhibited more residual or slight epicondylitis symptoms upon examination.     

Adjuvant therapy for osteosarcoma in dogs: results of randomized clinical trials using combined liposome-encapsulated muramyl tripeptide and cisplatin

Two randomized, double-blind clinical trials in dogs with spontaneous appendicular osteosarcoma treated with combination chemoimmunotherapy are reported. In both trials, dogs without overt metastasis underwent complete amputation of the affected limb. In trial 1, 40 dogs were treated with cisplatin chemotherapy [(CDDP), 70 mg/m2 i.v. every 28 days x 4]. Following CDDP, dogs without evidence of overt metastasis (n = 25) were randomized to receive liposome-encapsulated muramyl tripeptide phosphatidylethanolamine ](L-MTP-PE), 2 mg/m2 i.v.) or placebo liposomes (lipid equivalent) twice weekly for 8 weeks. Of 14 dogs in the placebo group, 13 (93%) died of metastasis; the median survival time was 9.8 months. Of 11 dogs in the L-MTP-PE group, 8 (73%) developed metastasis; the median survival time was 14.4 months, which was significantly longer than that of the placebo group (P < 0.01). In trial 2, 64 dogs received CDDP (70 mg/m2 i.v. every 21 days x 4) and were randomized to concurrently receive L-MTP-PE (2 mg/m2 i.v.) twice or once weekly, or placebo liposomes once weekly for 8 weeks. Median survival times were 10.3, 10.5, and 7.6 months, respectively. There were no significant differences among the three treatment groups in trial 2. Survival times for dogs receiving L-MTP-PE in trial 1 were significantly longer than those for dogs in trial 2 that received four doses of CDDP concurrently with twice weekly L-MTP-PE (P < 0. 04). The results of the first trial confirm our previous observation that L-MTP-PE has antimetastatic activity in dogs with osteosarcoma when given following amputation. The results of the second trial demonstrate that there is no survival advantage of administering L-MTP-PE concurrently with CDDP.