Plasma chromium after glucose administration.

Sharp increases in the concentration of chromium in plasma were found in five subjects with normal glucose utilization after administration of glucose by mouth. This rise was not observed in two diabetics when glucose tolerance was impaired; however, it appeared when glucose tolerance was improved and when trace amounts of trivalent chromium were given as a dietary supple-ment. The source of chromium which became elevated was most likely an internal pool. Possibly there is a relation between chromium and insulin function.

Pineal gland: dibutyryl cyclic adenosine monophosphate stimulation of labeled melatonin production.

In organ cultures of intact rat pineal glands, N(6)O(2')-dibutyryl adenosine 3', 5'-monophosphate stimulates the conversion of tritiated trytophan to tritiated melatonin, as does L-norepinephrine. Potential sites of stimulation of melatonin production by dibutyryl cyclic adenosine monophosphate are discussed, based on observations that the dibutyryl analog also stimulates the conversion of serotonin labeled with carbon-14 to carbon-14-labeled melatonin without altering hydroxyin-dole-O-methyl transferase activity or intracellular accumulation of serotonin labeled with carbon-14.

Perspective on the 1986 Food and Drug Administration assessment of the safety of carbohydrate sweeteners: uniform definitions and recommendations for future assessments.

Carbohydrate sweeteners in the diet, which are sources of added sugars, have recently undergone changes that vary considerably among countries. The major driving force for these changes is a technological development that permits conversion of corn and other starches to sweeteners. Major changes in the type of sweeteners used in the United States began in the mid-1970s. In 1986 the US Food and Drug Administration comprehensively evaluated exposures and potential health effects of sugars contained in carbohydrate sweeteners. A UK Department of Health report followed in 1989. An overview of issues is provided, terminologies used to describe sugars and sweeteners are defined, the findings of the US and UK reports are reviewed, trends in the availability of added and naturally occurring sugars are evaluated, and recommendations for future assessment of sugars are discussed. The potential problem of underreporting of food intakes in national food consumption surveys is also reviewed.

The public health significance of dietary fructose.

It is increasingly appreciated that some foods and food components, including fructose, have specific health benefits and/or potential risks. This recognition is associated with varied health claims and cautionary statements that can drive dynamic changes in food manufacture, selection, consumption, and views about food safety. It is imperative that the scientific and public health communities develop clear standards for evaluating potential benefits and risks, a process for accurately conveying sound public health information to consumers, and a mechanism for monitoring future changes in the food supply and relating these changes to potential health effects. In this paper we discuss specific and general considerations about the health effects of dietary fructose and provide a perspective on their public health significance. On the basis of currently available information, there is little basis for recommending increased or decreased use of fructose in the general food supply or in products for special dietary use.

Urinary chromium excretion of human subjects: effects of chromium supplementation and glucose loading.

The utilization of inorganic chromium by free-living human subjects was studied in 76 volunteers (male, 48; female, 28) who were supplemented with 200 micrograms of inorganic chromium as chromic chloride or a placebo tablet for 3 months in a double-blind, cross-over experiment. For all subjects, initial mean +/- SEM urinary chromium (Cr) level was 0.20 +/- 0.01 (range, 0.05 to 0.58) ng/ml and did not differ by sex. Initial chromium/creatinine ratio (Cr/Ct) was 0.15 +/- 0.01 (range 0.03 to 0.36) ng Cr/mg creatinine for females and was significantly lower, 0.10 +/- 0.01 (range 0.03 to 0.36) for males. Mean urinary Cr level increased to 1.0 +/- 0.12 after 2 and to 1.13 +/- 0.08 ng/ml after 3 months' supplementation. The Cr/Ct ratio increased to 0.69 +/- 0.10 for females and to 0.50 +/- 0.04 for males after 2 months' supplementation; values were similar after 3 months. An increase in urinary Cr excretion in response to a glucose load was demonstrated for nonsupplemented normal free-living subjects but not for subjects supplemented daily with trivalent chromium. Urinary Cr excretion after a glucose challenge was not predictable and did not depend on Cr status.

Dietary guidelines for infants: a timely reminder.

The 1995 edition of Dietary Guidelines for Americans has recently been released. In anticipation of the heightened attention that these revised will undoubtedly receive, there is renewed discussion about the need for Dietary Guidelines for Infants. These guidelines would reinforce to parents and nutrition professionals that many diet strategies designed to promote adult health and nutrition are inappropriate for infants and children under the age of two. These guidelines, developed in 1994 by the Gerber Products Company, seek to distinguish the unique dietary needs of this vulnerable population.

Regulation of rat liver glycogen synthesis and activities of glycogen cycle enzymes by glucose and galactose.

Direct regulation of rat liver glycogen metabolism by glucose and galactose was studied using an isolated liver perfusion system. Activation of glycogen synthase and net glycogen synthesis increased linearly when perfusate glucose concentration was increased from 125 to 500 mg/100 ml. Galactose, rapidly taken up by isolated rat liver regardless of circulating glucose concentration, increased these responses to glucose. In the presence of galactose (greater than or equal to 5 mg/100 ml), activation of synthase and glycogen synthesis were 1.5-fold higher at any given glucose concentration. The addition of insulin did not appreciably after synthase activation by glucose and galactose. Phosphorylase activity, low at circulating glucose levels above 125 mg/100 ml, was further decreased as glucose was increased or when galactose was added to the perfusate. Release of glucose into the perfusate in response to aglycemia was increased in the presence of galactose.

Chromium supplementation of human subjects: effects on glucose, insulin, and lipid variables.

Seventy-six normal, free-living subjects were given supplements of 200 micrograms chromium (Cr) in the form of chromic chloride or a placebo in a double-blind crossover study with 3-month experimental periods. Twenty of the 76 subjects had serum glucose concentrations greater than or equal to 100 mg/dL 90 minutes after a glucose challenge (1 g glucose per kilogram of body weight). Chromium supplementation significantly decreased (P less than 0.05) the 90-minute glucose concentration of these subjects from 135 +/- 9 to 116 +/- 11 mg/dL; fasting glucose concentrations also decreased significantly. The 90-minute serum glucose levels of the 35 subjects with glucose concentrations less than the fasting serum glucose level were increased significantly by Cr supplementation, from 71 +/- 1 to 81 +/- 4 mg/dL. Fasting and 90-minute serum glucose concentrations of the remaining subjects who displayed 90-minute glucose concentrations greater than fasting levels but less than 100 mg/dL were not affected by Cr supplementation. In this study, immunoreactive serum insulin concentration, body weight, lipids, and other selected clinical variables did not change significantly during Cr supplementation. These data demonstrate that Cr supplementation decreases the serum glucose levels of subjects with 90-minute glucose concentrations greater than or equal to 100 mg/dL following a glucose challenge, increases serum glucose levels of subjects with 90-minute glucose concentrations less than fasting levels, and has no effect on the serum glucose levels of subjects with 90-minute glucose values similar to but greater than fasting levels.

Protein inhibitors of phosphorylase phosphatase and cyclic AMP-dependent protein kinase from rabbit skeleta muscle.

A heat-and acid-stable protein inhibitor of phosphorylase phosphatase is present in a highly purified preparation of protein inhibitor of cyclic AMP-dependent protein kinase from rabbit skeletal muscle. Although these two inhibitors have strikingly similar properties to each other, such as sensitivity to trypsin and behavior on gel permeation chromatography, they can be separated by polyacrylamide disc gel electrophoresis. This indicates that the phosphatase-inhibitory and kinase-inhibitory activities reside with different protein species. The inhibition of both the enzymes is not altered by incubating the inhibitor preparation with a general phosphoprotein phosphatase, with phosvitin kinase, or with cyclic AMP-dependent protein kinase. Inhibition of phosphorylase phosphatase is of a non-competitive type supporting the idea that the phosphatase inhibitor is not an alternative substrate for the enzyme. Inhibition of phosphatase activity is selective in that it does no occur when phosphorylated histone or phosphorylated protamine are used as substrates.

Inhibition of rabbit skeletal muscle phosphorylase phosphatase by spermine.

The effect of three naturally occurring polyamines (putrescine, spermidine, and spermine) on the activity of rabbit skeletal muscle phosphorylase phosphatase was investigated. Only spermine significantly inhibited the enzyme. The mode of inhibition (ki value of 0.3 mM) of the phosphatase by spermine appears to be different from that caused by divalent metal ions or by other organic cations, such as arginine and lysine esters, since it is noncompetitive with respect to the substrate, phosphorylase a.

Enteric infections and other cofactors in AIDS.

It is generally accepted that human T-cell lymphotropic virus type III (HTL VIII) is the causative agent of acquired immunodeficiency syndrome (AIDS), but, asyet, there are no clear reasons for the different clinical manifestations of AIDS among individuals. In this article Douglas Archer and Walter Glinsmann discuss the history of AIDS and propose a link between HTLV-III infection and gastrointestinal disease processes with attendant malabsorption. They further propose that maximizing the nutritional status and minimizing the incidence of gastrointestinal infection of individuals infected with HTLV-III may prevent development of the full-blown AIDS.