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Biomedical subjects

A M Smith

Publications and source records attributed to A M Smith.

At least 361 records · Page 20Linked to original sources
PubMed1983

Monoclonal antibodies specific for tight-binding human chromatin antigens reveal structural rearrangements within the nucleus during the cell cycle.

The class of nonhistone chromosomal proteins that remains bound to DNA in chromatin in the presence of 2.5 M NaCl-5 M urea has proven refractile to biochemical analysis. In order to study its role in chromatin organization, we have produced monoclonal antibodies that are specific for the HeLa DNA-protein complex that remains after extraction of chromatin with high salt and urea. The antibody-producing clones were identified with an ELISA assay. Of the six clones selected, five were stabilized by limiting dilution. All clones are IgG producers. None cross-react significantly with native DNA, core histones, or the high-mobility group nonhistone proteins. All antibodies are specific for nuclear or juxtanuclear antigens. Indirect immunofluorescence shows that three antibodies, which are nonidentical, stain three different nuclear networks. Available evidence indicates that two of these networks are the nuclear matrix. A fourth antibody reveals structures reminiscent of chromocenters. A fifth antibody, AhNA-1, binds to interphase HeLa chromatin and specifically decorates metaphase chromosomes. AhNA-1 similarly recognizes rat chromosomes. Each of these monoclonal antibodies also reveals a changing pattern of nuclear staining as cells progress through the cell cycle. Presumably, this reflects the rearrangement of the cognate antigens.

Animals↗
PubMed1983

Monitoring variations of biological impedances using microwave Doppler radar.

A microwave Doppler radar for continuously monitoring time-varying biological impedances is described. The radar compares the phase of the signal scattered from a region of biological tissue with that of the transmitted signal. The phase changes of the scattered signal are an indication of the net impedance changes within the test region due to various physiological processes, for example, the displacements of blood vessels during the cardiac cycle. A Doppler radar, equipped with a matched antenna, was tested with a simulation model and its detection characteristic was found to be a sinusoidal function of the antenna-object spacing. Tests with healthy human subjects were also performed at 3 GHz and 10.5 GHz. It was found that the 3 GHz Doppler radar has significantly greater penetration in tissues but is less sensitive to changes of the biological impedance than the 10.5 GHz system.

Doppler Effect↗
PubMed1983

Folate depletion secondary to iron deficiency in the neonatal rat.

Two experiments were performed to investigate the effect of dietary iron deficiency during reproduction on folate status in rat dams and pups. In experiment 1, twenty pregnant Sprague-Dawley rats (190-200 g) were fed one of two diets (8 ppm Fe, 1 ppm folate or 250 ppm Fe, 1 ppm folate) throughout gestation and until day 18 of lactation when dams and their pups (seven per litter) were killed. Although there was no effect of iron deficiency on dam folate status, iron-deficient pups had decreased liver folate activity compared to controls. Milk free folate activity was significantly decreased by 34% in iron-deficient dams compared to controls. To determine if iron deficiency affected folate status at birth, experiment 2 was conducted. Nine pregnant rats (215-230 g) were fed one of two diets (6 ppm Fe, 1 ppm folate or 250 ppm Fe, 1 ppm folate) throughout gestation and until day 2 of lactation. Liver and kidney folate activities were similar in both groups of pups on day 2 of lactation. It is concluded that the stress of lactation superimposed on iron deficiency alters the folate composition of rat milk, and results in folate depletion in 18-day-old rat pups.

Animals↗
PubMed1983

Use of murine myeloma protein M467 for detecting Salmonella spp. in milk.

This investigation introduces the use of an immunoglobulin A mouse myeloma protein for the detection of Salmonella spp. in milk. The immunoglobulin A protein M467 reacts with flagellin from a wide variety of serotypes. Two assays were developed which used an enzyme-linked immunosorbent assay (ELISA) and M467. Alkaline phosphatase was conjugated to M467 (M467-PH), and the presence of Salmonella dublin was detected by a competitive solid-phase ELISA and a membrane filtration ELISA. The competitive assay competed viable Salmonella spp. found in contaminated milk against polymerized flagellin or whole bacteria fixed to polyvinyl plates for binding by M467-PH. The membrane filtration method utilized a hydrophilic membrane for filtering the bacteria, which were then detected by the reaction with M467-PH and substrate. The sensitivity of the competitive solid-phase ELISA was 10(3) bacteria ml-1, whereas the filter membrane assay required the media containing the bacteria to be cultured in enrichment medium for 4 h before the assay to ensure detection. Either assay could be run within a typical 8-h work day. The filter membrane assay was not suitable for milk due to the high level of natural alkaline phosphatase activity in the liquid food.

Animals↗
PubMed1983

School meals and the rate of growth of primary school children.

The effect of school meals on the rate of growth was assessed in two sets of children over one, two, and three-year periods in England and Scotland between 1973 and 1979. In all analyses children were subdivided into three groups: poor, not poor, and undefined, according to a set of questions on social circumstances. The rate of growth was assessed for children receiving school meals, lunches prepared at home, and those who changed scheme during the study period. No relation between rate of growth and uptake of school meals was found at any of the levels of poverty in England. In Scotland there was some indication in the poor group that children who received school meals had a smaller rate of growth than children having lunches prepared at home. There was inconclusive evidence that children from the poorer sectors of the community whose mother's worked outside the home may benefit from the school meals system. Although children selected for welfare support were smaller than other children, in so far as the design of the study allowed school meals during the 1970s did not increase the rate of growth of primary school children in any social stratum.

Body Height↗
PubMed1983

IgE myeloma associated with plasma cell leukaemia.

A patient presented with plasma cell leukaemia and was found to have an IgE secreting multiple myeloma. IgE myeloma is very rare with only 18 cases recorded. However, this case is the fifth recorded of IgE myeloma associated with plasma cell leukaemia. Since plasma cell leukaemia only occurs in 1.6% of all cases of myeloma, it seems certain that this is a significant association.

Aged↗
PubMed1983

Enzyme immunoassay for carcinoembryonic antigen.

In this rapid, simple enzyme immunoassay for carcinoembryonic antigen (CEA) in serum the "sandwich" system is used. The CEA is first extracted from the serum into acetate buffer by heating at 70 degrees C, then incubated in a polyvinyl microtitration plate previously coated with anti-CEA. The bound CEA is then reacted with anti-CEA conjugated to horseradish peroxidase and the activity of the peroxidase bound to the wells of the plate is quantified by adding the enzyme substrate. The assay is sensitive to 3.1 micrograms/L (which can be improved to 0.39 microgram/L by prolonging the incubation times to 120 min), precise (between-assay CV 8.0%), and shows adequate analytical recoveries. Results compared favorably with those by a radioimmunoassay kit (Abbott Diagnostics), r = 0.99. The reference interval for serum CEA in normal adults is shown. This assay is appropriate for use in monitoring patients with colorectal tumors after surgery.

Carcinoembryonic Antigen↗
PubMed1983

Interaction between motor commands and somatosensory afferents in the control of prehension.

In 1931, Hughlings Jackson made a distinction between voluntary and automatic movements. According to Jackson the former are varied and purposeful gestures, whereas the latter include stereotyped movements largely under immediate sensory control. In this regard it may be said that the motor function of the primate hand includes both voluntary as well as automatic responses. Phillips and Porter (1977) noted that injury to the nervous system may often disrupt tactile exploration and skilled manipulation, although the same lesion may fail to interfere with automatic prehension used in posture and locomotion. The effects of selective brain destruction as well as the results from single-cell recordings from moving animals have indicated some of the different contributions made by various parts of the cerebello-thalamo-cortical motor system. Prehension offers a unique opportunity in which the interactions between motor commands and somatosensory afferents may be studied.

Afferent Pathways↗
PubMed1983

Folate supplementation during lactation: maternal folate status, human milk folate content, and their relationship to infant folate status.

The influence of maternal folate status and human milk folate content on infant folate status was studied in 11 lactating women taking folate supplements throughout pregnancy and lactation. Nursing mothers not taking folate supplements, as well as nonpregnant, nonlactating women, were also studied. Maternal and infant serum and red blood cell (RBC) folate concentrations, as well as the "free" and total folate contents of human milk samples, were determined at 6 and 12 weeks post partum. Mothers taking folate supplements maintained blood folate concentrations higher than those of unsupplemented mothers and similar to or higher than those of normal adults. Infants of both supplemented and unsupplemented mothers maintained similar blood folate levels. Positive correlations were found between maternal RBC folate concentrations and infant RBC folate concentrations at 6 weeks (r = 0.62) and 3 months (r = 0.74), but no relationship was found between maternal folate status and human milk folate activity. Human milk folate levels increased with the progression of lactation, were higher in the evening than earlier in the day, and were higher at the end of a feeding than at the beginning. These results indicate that human milk folate levels are maintained at the expense of maternal reserves and that folate supplementation during lactation may be of value for preservation of maternal reserves.

Adult↗
PubMed1982

Oxidation of indole-3-acetic acid by peroxidase: involvement of reduced peroxidase and compound III with superoxide as a product.

Kinetic and spectral data establish that peroxidase may oxidize indole-3-acetic acid by either of two pathways depending on the enzyme/substrate ratio. When relatively low enzyme/substrate ratios are employed, the oxidation proceeds through a reduced peroxidase in equilibrium compound III shuttle. Conversely, peroxidase operates through the conventionally accepted pathway involving native enzyme and compounds I and II only when high enzyme/substrate ratios are used. Compound III, a specific oxidase, constitutes the dominant steady-state form of peroxidase when the reduced peroxidase in equilibrium compound III shuttle is operational. Activation of this shuttle also produces a flux of superoxide anion radical at the expense of molecular oxygen. Thus, important biological consequences may follow activation of this shuttle under physiological conditions.

Catalase↗