Buford L. Nichols

Nuclear Magnetic Resonance Transverse Relaxation Times of Water Protons in Skeletal Muscle

The observation of the spin-echo decay in a long time domain has revealed that there exist at least three different fractions of non- (or slowly) exchanging water in the rat gastrocnemius muscle. These fractions of water are characterized with different nuclear magnetic resonance (NMR) relaxation times and are identified with the different parts of tissue water. The water associated with the macromolecules was found to be approximately 8% of the total tissue water and not to exchange rapidly with the rest of the intracellular water. The transverse relaxation time (T(2)) of the myoplasm is 45 ms which is roughly a 40-fold reduction from that of a dilute electrolyte solution. This fraction of water accounts for 82% of the tissue water. The reduced relaxation time is shown neither to be caused by fast exchange between the hydration and myoplasmic water nor by the diffusion of water across the local magnetic field gradients which arise from the heterogeneity in the sample. About 10% of the tissue water was resolved to be associated with the extracellular space, the relaxation time of which is approximately four times that of the myoplasm. Mathematical treatments of the proposed mechanisms which may be responsible for the reduction of tissue water relaxation times are given in this paper. The results of our study are consistent with the notion that the structure and/or motions of all or part of the cellular water are affected by the macromolecular interface and this causes a change in the NMR relaxation rates.

Immunologic factors in human milk during the first year of lactation

The effects of the duration of lactation upon lactoferrin, lysozyme, total IgA, SIgA, SIgA antibodies to Escherichia coli somatic antigens and leukocytes in human milk were investigated. Longitudinal and cross-sectional studies were performed with milk collected from women 20 to 35 years of age during te first year of lactation. Collection and storage conditions and immunologic analyses were controlled to minimize confounding variables. The concentrations of lactoferrin, total IgA, and leukocytes and the uptake of 3H-thymidine by phytohemagglutinin-stimulated lymphocytes fell during the first several weeks of lactation; afterward, the levels of lactoferrin and IgA stabilized. Approximately 90% of total IgA in human milk during the year was SIgA. Secretory IgA antibody titers to E. coli increased in some individuals studied longitudinally suggesting that the enteromammary gland pathway of SIgA antibody production was active after several weeks of lactation. Moreover, the concentrations of lysozyme, after falling to a nadir of 20 to 30 micrograms/ml at 2 to 4 weeks, rose to 200 to 300 micrograms/ml by six months and remained elevated. The immunologic system in human milk undergoes remarkable changes which may represent adaptations for the recipient infant.

Human milk intake and growth in exclusively breast-fed infants

Milk intake and growth in 45 exclusively breast-fed infants were documented during the first 4 months of life. Energy and protein intakes were substantially less than current nutrient allowances. Energy intake declined significantly from 110 +/- 24 kcal/kg/day at 1 month to 71 +/- 17 kcal/kg/day at 4 months. Protein intake decreased from 1.6 +/- 0.3 gm/kg/day at 1 month to 0.9 +/- 0.2 gm/kg/day at 4 months. Infant growth progressed satisfactorily, compared with National Center for Health Statistics standards. A reevaluation of energy and protein intakes and allowances during infancy is merited.

Human Lactoferrin Stimulates Thymidine Incorporation into DNA of Rat Crypt Cells

Abstract: In a search for dietary factors that might stimulate enterocyte proliferation, we developed an assay for thymidine incorporation into DNA using harvested crypt cells from mature rat small intestine. Human colostrum stimulated a significant increase in thymidine incorporation into rat crypt cell DNA during a 60-min period of incubation. When the protein with biological activity was purified to a single peak by sequential ion exchange and gel filtration chromatography, it was found to have the characteristics of lactoferrin. The protein was identical to lactoferrin standards by sodium dodecyl sulfate polyacrylamide gel electrophoresis, isoelectric focusing, and doublediffusion immunologic precipitation. All available human lactoferrins stimulated thymidine uptake and all reacted with a lactoferrin polyclonal antibody. Human lactoferrin appears to be a potent activator of thymidine incorporation into DNA in incubated rat crypt cells, a nutritional function not previously reported.

Preliminary study of breastfeeding and bacterial adhesion to uroepithelial cells

The oligosaccharide content of breast-milk and urine from ten nursing mothers and their babies, collected 30 days after delivery, was analysed by thin-layer and high-performance liquid chromatography. Each womans milk and urinary oligosaccharide profiles were very similar, and the pattern of oligosaccharides excreted by her infant was also strongly correlated with that of her milk. The babies excreted 300-500 mg/day oligosaccharides and the mothers 500-800 mg/day. The effect of oligosaccharide fractions from a 500 ml pool of colostrum on bacterial adhesion to uroepithelial cells was tested on a strain of Escherichia coli isolated from an infant with urinary tract infection. The high-molecular-weight sialylated oligosaccharides had no effect but neutral oligosaccharides caused inhibition of bacterial adhesion which rose as the size of the oligosaccharides decreased. These findings suggest that breastfeeding may have a preventive effect on urinary tract infection in both mother and infant.

The maltase-glucoamylase gene: common ancestry to sucrase-isomaltase with complementary starch digestion activities.

Brush-border maltase-glucoamylase (MGA) activity serves as the final step of small intestinal digestion of linear regions of dietary starch to glucose. Brush-border sucrase-isomaltase (SI) activity is complementary, through digestion of branched starch linkages. Here we report the cloning and sequencing of human MGA gene and demonstrate its close evolutionary relationship to SI. The gene is ≈82,000 bp long and located at chromosome 7q34. Forty-eight exons were identified. The 5′ gene product, when expressed as the N-terminal protein sequence, hydrolyzes maltose and starch, but not sucrose, and is thus distinct from SI. The catalytic residue was identified by mutation of an aspartic acid and was found to be identical with that described for SI. The exon structures of MGA and SI were identical. This homology of genomic structure is even more impressive than the previously reported 59% amino acid sequence identity. The shared exon structures and peptide domains, including proton donors, suggest that MGA and SI evolved by duplication of an ancestral gene, which itself had already undergone tandem gene duplication. The complementary human enzyme activities allow digestion of the starches of plant origin that make up two-thirds of most diets.

Longitudinal changes in milk composition of mothers delivering preterm and term infants

The concentrations of protein nitrogen (PN), non-protein nitrogen (NPN), energy, fat, sodium (Na), calcium (Ca), phosphorus (P), magnesium (Mg), and zinc (Zn) were determined in human milk from mothers giving birth to full-term (n = 13) and preterm infants (n = 8). Milk samples were collected under controlled conditions at two-week intervals for 12 weeks postpartum. Statistically significant differences in PN, Ca, and P concentrations were detected between the milk from mothers of preterm and term infants. The mean PN concentration in the preterm milk was statistically higher than that of term milk (198 vs. 164 mg N/dl), in contrast to the lower mean Ca (220 vs. 261 mg/l) and P (125 vs. 153 mg/l) concentrations detected in the preterm milk. No other differences in mean nutrient concentration were observed between the two groups. Concentrations of PN, NPN, Na, P, and Zn decreased over time. The concentration of Mg increased slightly. The content of fat, energy, and Ca did not change.

Distinction between the Preneoplastic and Neoplastic State of Murine Mammary Glands

We have, using nuclear magnetic resonance spectroscopy, measured the relaxation times and diffusion coefficient of water protons in primary mammary adenocarcinomas of mice. In our biological model, three morphological stages were defined: (a) mammary gland tissue from pregnant mice, (b) preneoplastic nodules, and (c) neoplastic tissue. It was found that neoplastic tissues could be distinguished from normal and prenoeplastic tissue. Spin-spin and spin-lattice relaxation times and the diffusion coefficient of water protons are increased in the neoplastic tissue relative to mammary gland tissue from pregnant mice and preneoplastic nodule tissue.

Cholesterol ester storage disease: Clinical, biochemical, and pathological studies

Of three siblings affected with cholesterol ester storage disease, two died at ages 7 and 9 years, respectively, with hepatic scarring and portal hypertension. Lipid storage was documented in both patients, as were esophageal varices and aortic plaques in the older child. The third affected sibling, followed to 13 years of age, has hepatomegaly, hyperlipidemia, short stature, adrenal calcification, and acid lipase deficiency. Leukocyte extracts demonstrated deficiency of acid lipase in this patient. This autosomal recessive condition may be allelic with Wolman disease with a more malignant course in this family than in most reported cases.

Nutrient intake and growth performance of older infants fed human milk

Study objective: To determine whether the ad libitum addition of solid foods to the diet of exclusively human milk-fed infants will increase energy intake and reverse the decline in weight-for-age percentiles observed during the exclusive breast-feeding period. Design: Weekly or biweekly measures of growth were made longitudinally on a cohort of infants from birth to 36 weeks of age, and monthly measures of nutrient intake were made from 16 weeks of age until 10 weeks after solid foods were introduced into the diet. Subjects: Volunteer mother-infant pairs from middle and upper income groups who met entry criteria, including the intention to breast-feed exclusively for at least for 16 weeks; 58 pairs entered and 45 pairs completed the study. Intervention : Solid foods were introduced at a time determined by the mother and the pediatrician; solid foods from controlled lot numbers were provided for each infant. Measurements and main results: After solid foods were added, daily human milk intake declined at a rate of 77 gm/mo ( p Conclusions: Energy intake of human milk-fed infants did not increase after solid foods were added to their diet but was maintained at approximately 20% below recommended levels. Energy intake appeared to reflect infant demands. These data suggest that the recommendations for the energy requirements of infancy should be reevaluated. The growth pattern of exclusively breast-fed infants differs from that of the National Center for Health Statistics reference population. These observations raise questions about the adaptive response of human milk-fed infants to different levels of energy intake and about the estimations of energy requirements based on the sum of basal metabolism, activity, growth, and diet-induced thermogenesis.