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Biomedical subjects

F R Smith

Publications and source records attributed to F R Smith.

At least 19 recordsLinked to original sources
PubMed1994

Cyanomet human hemoglobin crystallized under physiological conditions exhibits the Y quaternary structure.

Cyanomet human hemoglobin has been crystallized at a chloride ion concentration and pH similar to physiological conditions. Molecular replacement calculations definitively show that the hemoglobin subunits are arranged in the Y quaternary form recently discovered in carbon monoxy hemoglobin Yp-silanti (beta 99 Asp-Tyr), and subsequently observed in carbon monoxy normal human hemoglobin crystallized at low ionic strength and low pH. The structure has been refined at 2.09 A resolution to an R-value of 0.232, and further refinement is currently underway. Although the refinement is not yet complete, our results are the first indication that the Y structure may represent an important quaternary form of liganded hemoglobin under physiological buffer conditions. These results suggest the need for a reexamination of structure-function correlations in the hemoglobin system.

Buffers↗
PubMed1993

Perceptual processing of pattern goodness by left and right hemispheres.

Two experiments tested perceptual processing of Garner and Clement's (1963) good and poor five-dot patterns by the left and right hemispheres. Two (good) patterns were from four-member equivalence sets, and the other (poor) pattern was from an eight-member equivalence set. One of the good patterns formed a T shape that could be processed as a linguistic unit. In Experiment 1, 80 right-handed subjects made same-different judgments for lateralized 200-msec paired presentations of these patterns. When both presentations were to the RVF/LH, response latency was faster for the T pattern than for the other two. When both presentations were to the LVF/RH, response latency was faster for the two good patterns than for the poor pattern. When the first pattern was presented to the RVF/LH and the second was presented to the LVF/RH, response latencies were lower for the two good patterns than for the poor pattern. Also, when the first pattern was presented to the LVF/RH and the second was presented to the RVF/LH, response latency was faster for the T pattern than for the other good pattern which was, in turn, faster than for the poor pattern. Experiment 2 used a duration judgment task (Avant & Lyman, 1975) to test effects of pattern goodness on apparent durations of pre- and postmasked 10-msec pattern presentations. With left hemisphere inputs, presentations of good patterns were judged to be longer than presentations of the poor pattern. When each hemisphere compared the T and the other good pattern, presentations of the T pattern were judged to be longer, and the right hemisphere further discriminated among pattern orientations. Presentations of the T pattern to each hemisphere were judged to be longer than presentations of the poor pattern, and both hemispheres discriminated among orientations of both patterns. These results indicate that the two hemispheres can, during perceptual processing, function cooperatively, and that both prerecognition and conscious perceptual operations are guided by task demands.

Adult↗
PubMed1993

Expected duration of hospital stay of low birth weight infants: graphic depiction in relation to birth weight and gestational age.

Neonatal duration of hospital stay correlated with both birth weight and gestational age in positively skewed, nonlinear relationships. Within increments of birth weight, gestational age had a semi-independent influence on length of stay. Log length of stay correlated with both birth weight and gestational age in linear, normally distributed relationships. A nomogram is provided for predicting individual lengths of stay.

Analysis of Variance↗
PubMed1992

Mutagenic dissection of hemoglobin cooperativity: effects of amino acid alteration on subunit assembly of oxy and deoxy tetramers.

Free energies of oxygen-linked subunit assembly and cooperative interaction have been determined for 34 molecular species of human hemoglobin, which differ by amino acid alterations as a result of mutation or chemical modification at specific sites. These studies required the development of extensions to our earlier methodology. In combination with previous results they comprise a data base of 60 hemoglobin species, characterized under the same conditions. The data base was analyzed in terms of the five following issues. (1) Range and sensitivity to site modifications. Deoxy tetramers showed greater average energetic response to structural modifications than the oxy species, but the ranges are similar for the two ligation forms. (2) Structural localization of cooperative free energy. Difference free energies of dimer-tetramer assembly (oxy minus deoxy) yielded delta Gc for each hemoglobin, i.e., the free energy used for modulation of oxygen affinity over all four binding steps. A structure-energy map constructed from these results shows that the alpha 1 beta 2 interface is a unique structural location of the noncovalent bonding interactions that are energetically coupled to cooperativity. (3) Relationship of cooperativity to intrinsic binding. Oxygen binding energetics for dissociated dimers of mutants strongly indicates that cooperativity and intrinsic binding are completely decoupled by tetramer to dimer dissociation. (4) Additivity, site-site coupling and adventitious perturbations. All these are exhibited by individual-site modifications of this study. Large nonadditivity may be correlated with global (quaternary) structure change. (5) Residue position vs. chemical nature. Functional response is solely dictated by structural location for a subset of the sites, but varies with side-chain type at other sites. The current data base provides a unique framework for further analyses and modeling of fundamental issues in the structural chemistry of proteins and allosteric mechanisms.

Hemoglobins↗
PubMed1991

The mutation beta 99 Asp-Tyr stabilizes Y--a new, composite quaternary state of human hemoglobin.

Carbonmonoxy hemoglobin Ypsilanti (beta 99 Asp-Tyr) exhibits a quaternary form distinctly different from any structures previously observed for human hemoglobins. The relative orientation of alpha beta dimers in the new quaternary form lies well outside the range of values observed for normal unliganded and liganded tetramers (Baldwin, J., Chothia, C., J. Mol. Biol. 129:175-220, 1979). Despite this large quaternary structural difference between carbonmonoxy hemoglobin Ypsilanti and the two canonical structures, the new quaternary structure's hydrogen bonding interactions in the "switch" region, and packing interactions in the "flexible joint" region, show noncovalent interactions characteristic of the alpha 1 beta 2 contacts of both unliganded and liganded normal hemoglobins. In contrast to both canonical structures, the beta 97 histidine residue in carbonmonoxy hemoglobin Ypsilanti is disengaged from quaternary packing interactions that are generally believed to enforce two-state behavior in ligand binding. These features of the new quaternary structure, denoted Y, may therefore be representative of quaternary states that occur transiently along pathways between the normal unliganded, T, and liganded, R, hemoglobin structures.

Allosteric Site↗
PubMed1990

The use of hyaluronidase in the treatment of intravenous extravasation injuries.

Intravenous extravasation injuries are a major cause of morbidity in the pediatric population. A variety of commonly used drugs and intravenous fluids have been shown to cause injury, particularly when infants are infused subcutaneously. Optimal management of intravenous extravasations remains controversial. The enzyme hyaluronidase degrades hyaluronic acid, a constituent of the normal interstitial barrier; by degrading interstitial bonds, it can increase the distribution and absorption of locally injected substances. To test the hypothesis that hyaluronidase might prevent skin injury associated with extravasations, a reliable skin injury model in immature pigs was created using subcutaneous CaCl2 injections. Hyaluronidase, in a concentration of 150 U/mL injected subcutaneously in a circumferential fashion immediately following the injection of CaCl2, significantly reduced the area of necrosis (P less than .01). As a control for the diluent volume administered with the hyaluronidase injection, the effect of a circumferential injection of 1.0 mL normal saline was compared with a similar injection of 1.0 mL normal saline with 150 units of hyaluronidase. Again, the area of skin necrosis following injection with hyaluronidase was statistically smaller (P less than .01). We have created a reliable skin injury model using immature porcine skin, which resembles human skin. Our data using this model suggest that the use of hyaluronidase may decrease the morbidity associated with intravenous extravasation injuries.

Animals↗
PubMed1989

Superior vena cava syndrome in infants.

Superior vena cava syndrome is uncommon in infants. With the increased use of central venous catheters, however, there has been an increased incidence of central venous occlusion. We report a case of superior vena cava syndrome occurring on two separate occasions in a premature infant with an indwelling central line. We discuss current concepts of prevention and management.

Catheterization, Central Venous↗
PubMed1987

Three-state combinatorial switching in hemoglobin tetramers: comparison between functional energetics and molecular structures.

In a previous study on cyanomethemoglobin the 10 tetrameric species (each with a unique combination of ligated and unligated subunits) were found to exhibit three distinct free energies of cooperative interaction. The distribution of these free energies among the partially ligated species is incompatible with a two-state mechanism of molecular switching and requires a minimum of three molecular structures with distinctly different free energies of heme-heme interaction. Ligand-linked transitions between the three cooperativity states were found to be "combinatorial"--i.e., dependent upon changes in both the number and specific configuration of bound ligands. Here we present results from two other chemical systems that mimic intermediate oxygenation states. In these systems the heme iron is replaced by manganese in certain of the subunits. We find the same distribution of cooperative free energies as reported for the cyanomethemoglobin system. These results demonstrate that the three-state combinatorial nature of cooperative switching is neither a special feature of the cyanomet reactions nor of the substitution of manganese for iron, but reflects a fundamental property of hemoglobin. These findings are compared with crystallographic structural results on partially ligated hemoglobins.

Energy Metabolism↗
PubMed1987

Congenital absence of the left coronary artery.

Congenital absence of the left coronary artery system and the prevalence of a single right coronary artery to supply the heart is a rare anomaly. There is not yet enough data to determine its importance because only a few have been found in living patients. This is just such a case, diagnosed premortem in an otherwise healthy coronary system with no other physical abnormalities.

Coronary Vessel Anomalies↗
PubMed1986

Selective immunomodulation by the antineoplastic agent mitoxantrone. II. Nonspecific adherent suppressor cells derived from mitoxantrone-treated mice.

Mitoxantrone exerts a potent suppressive influence upon humoral immune responses. The B cell is a likely target for this inhibitory effect, and we have reported evidence supporting this possibility. The impact of mitoxantrone upon T lymphocyte reactivity was assessed as a second mode of action of this novel antineoplastic drug. TH and TS lymphocyte induction were tested in the in vitro anti-sheep erythrocyte response, and a surprising differential effect of mitoxantrone was observed. Helper activity was abrogated and suppressor function was enhanced. In apparent disagreement with this result, mitoxantrone inhibited the in vivo induction of TS cells using trinitrophenylated spleen cells. Macrophages were investigated as potential mediators of these effects upon immunoregulatory function. Replacement of macrophages in mitoxantrone-treated spleen cell preparations by normal adherent cells allowed the induction and complete expression of TH lymphocyte function. Conversely, replacement of mitoxantrone-treated macrophages with normal adherent cells before induction of TS cells failed to generate TS cell function. Thus, TH cells were resistant and TS cells were completely susceptible to mitoxantrone. Furthermore, supplementation of normal TH cell cultures with splenic macrophages from mitoxantrone-treated mice inhibited the induction of helper function. Production of the lymphokines IL 2 and TRF in mitoxantrone-treated mice was normal. This is consistent with the retention of functional TH cells in drug-treated spleens. Macrophages in the spleens of mitoxantrone-treated mice were responsible for the abrogated helper function and the enhanced suppressor activity. Although TS cell induction was directly inhibited by the drug, the effect upon TH cell function was secondary to the action of mitoxantrone-induced suppressor macrophages. Mitogen-stimulated lymphokine production was normal. Thus, mitoxantrone is a selective immunomodulator. The macrophage-mediated suppression of TH cell induction and humoral immunity investigated in spleens from mitoxantrone-treated mice is an intriguing finding that may have significant implications for immunotherapy.

Animals↗
PubMed1986

Resolving pathways of functional coupling within protein assemblies by site-specific structural perturbation.

Site-specific structural modification is a powerful tool for studying functional mechanisms in proteins where the structures may be manipulated by direct chemical modification, by selection of naturally-occurring mutants, or by site-directed mutagenesis. Here, we present a general strategy for such studies, which we term "mapping by structure-function perturbation." A series of functional perturbations (i.e., deviations of functional behavior from that of the native protein) are mapped against the structural locations of the modified sites, obtained over a range of locations. The modifications are treated as arbitrary perturbations of structure at specific locations, in contrast to the conventional approach of trying to interpret their local stereochemistry. The map yields information on structural locations of functional events and pathways of coupling within protein assemblies. We have applied this approach to the ligand-linked subunit assembly of human hemoglobin, using both chemically-modified heme sites (CN-met), and amino acid residues altered by mutation and chemical modification.

Hemoglobins↗
PubMed1985

Bacterial and viral pathogens causing fever in infants less than 3 months old.

We studied 182 sick, febrile (temperature greater than 38 degrees C) infants less than 3 months of age, who presented at our Tripler Army Medical Center, Honolulu, during a one-year period, to determine the relative causes of fever in this age group. Blood, cerebrospinal fluid, urine, nasopharyngeal secretions, and stool specimens were cultured for bacterial and viral pathogens. Paired acute and convalescent sera were collected to serologically confirm infection in infants from whom viral isolations were obtained only from the nasopharynx or stool. A viral pathogen was isolated in 75 infants (41%) and a bacterial pathogen was isolated in 27 infants (15%). Nonpolio enteroviruses were the most common pathogens demonstrated. They were isolated from 64 infants (35%), and 40 (62%) of these infants had aseptic meningitis, the most frequently made diagnosis. Urinary tract infection was the most common bacterial infection observed. It occurred in 20 infants (11%) and was most often seen without associated pyuria in uncircumcised male infants. Salmonellosis, the second most common bacterial infection, was observed in six infants (3%), and two of these did not have diarrhea or other gastrointestinal tract symptoms. No infant had septicemia and only one infant had bacterial (group B streptococcal) meningitis.

Bacterial Infections↗
PubMed1985

Experimental resolution of cooperative free energies for the ten ligation states of human hemoglobin.

Tetrameric human hemoglobin can assume ten molecular forms that differ in the number and configuration of ligands bound at the four heme sites. For each of these species we have determined the cooperative free energy--i.e., the deviation in free energy of ligation from that which would obtain for the same sites binding as independent alpha and beta subunits. These cooperative free energies were resolved from measurements on the dissociation into dimers of tetramers in which each subunit is either unligated (Fe2+ deoxy) or "ligated" by conversion into the cyanomet form (Fe3+ CN). The results indicate that each hemoglobin tetramer acts as a three-level molecular switch. During the course of ligation, the total cooperative free energy (6 kcal/mol over all four binding steps) is expended in two transitions that are synchronized with particular ligation steps. Whether a cooperative energy transition occurs or not depends upon how the ligation step changes both the number and configuration of ligated subunits. The hemoglobin tetramer is thus a "combinatorial switch." The finding of three distinct free energy levels for the ten ligation states suggests the existence of three major structural forms of the hemoglobin tetramer.

Hemoglobins↗
PubMed1985

A monoclonal antibody that recognizes an Ly-6-linked antigen inhibits the generation of functionally active T cell subsets.

A monoclonal antibody (mAb) generated against the chemically-induced BALB/c Meth A sarcoma, designated HD42, reacts in cytotoxic tests with Meth A as well as with BALB/c peripheral lymph node cells and mitogen-activated spleen cells. The antigen was detected by FACS analysis on BALB/c spleen and lymph node cells, and by absorption assays on all normal lymphoid cells of BALB/c but not B6 mice. The expression of the antigen was not found on normal adult lung fibroblasts, on brain, nor on an extensive panel of tumors of BALB/c and B6 origin. Because the strain distribution of the antigen is reciprocal to that of Ly-6.2 and is not expressed in congenic C3H.Ly-6b mice, we have tentatively defined it as Ly-6.1 and referred to the mAb as alpha-Ly-6.1. The presence of alpha-Ly-6.1 abrogates both the Con A-induced and the IL 2-dependent proliferative response of normal T cells, whereas the response of normal B cells to LPS remains unaffected. alpha-Ly-6.1 is a potent suppressor of the primary in vitro plaque-forming cell (PFC) response to SRBC. Pretreatment of normal splenic T cells with alpha-Ly-6.1 and complement had no effect on the ability of these cells to generate in vitro either T helper cells (TH) or T suppressor cells (TS) to SRBC. However, addition of antibody in the absence of complement during the generation of TH or TS, or posttreatment of these T cell subsets with antibody and complement after in vitro education, completely removed the functional activity of these cell types. Addition of alpha-Ly-6.1 to MLC suppressed the MLR as well as the generation of cytotoxic lymphocytes (CTL), whereas the presence of the antibody during a cell-mediated lympholysis (CML) had no effect. Therefore, it appears that alpha-Ly-6.1 recognizes an antigen that is important for the generation of TH and TS cell subsets.

Animals↗