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Biomedical subjects

R S Franco

Publications and source records attributed to R S Franco.

36 records · Page 2Linked to original sources
PubMed1989

Modification of the oxygen affinity and intracellular hemoglobin concentration of normal and sickle cells by means of an osmotic pulse.

Important properties of red blood cells (RBCs), including oxygen affinity and intracellular hemoglobin concentration, may be modified by means of an osmotic pulse. The pulse is developed by rapid dilution of a suspension of RBCs to which dimethylsulfoxide has been added. The nature and degree of RBC modification is dependent on the composition of the diluent solution. The purpose of this investigation was to explore the dependence of these changes on diluent composition and to determine the stability of altered cellular properties with in vitro incubation. For both normal control RBCs (A cells) and RBCs from patients with sickle cell anemia (S cells), cells with increased volume and markedly decreased intracellular hemoglobin concentration (65% to 70% of control) or with normal volume and moderately decreased hemoglobin concentration (80% to 85% of control) were prepared. These modifications were accomplished with hemoglobin yields ranging from 60% to 90%, depending on the diluent used, the cell type, and the intensity of treatment. For the same degree of inositol hexaphosphate (IHP) incorporation into A cells, as shown by the shift in oxygen half-saturation pressure (P50), diluent formulations with constant total osmolality but varying IHP concentration gave the same degree of hemoglobin loss per cell. Posttreatment cell size, however, ranged from slightly smaller than control to approximately 20% larger. On incubation, the larger cells returned toward normal size, whereas those with normal posttreatment size remained constant. S cells showed the same general changes with treatment and incubation but with greater variation. The treated S cells exhibited markedly reduced morphologic sickling on deoxygenation.

Adenosine Triphosphate↗
PubMed1988

The 24-hour posttransfusion survival and lifespan of autologous baboon red cells treated with inositol hexaphosphate-polyethylene glycol or inositol hexaphosphate-adenosine triphosphate-polyethylene glycol to decrease oxygen affinity.

Baboon red cells were treated to reduce oxygen affinity by an osmotic-pulse procedure using dimethyl-sulfoxide. Inositol hexaphosphate (IHP) alone or IHP and adenosine triphosphate (ATP) were incorporated into the red cells in the presence of polyethylene glycol (PEG). The procedure produced variable increases in the red cell P50 value, i.e., the partial pressure of oxygen at which 50% of the hemoglobin was saturated. The effect of treatment of autologous baboon red cells on the 24-hour posttransfusion survival value and lifespan T50 value was measured using a double-label procedure. The data demonstrate that the increase in the P50 value of treated red cells was negatively correlated with the 24-hour posttransfusion survival value; the higher the P50 value, the poorer the 24-hour posttransfusion survival value. The 24-hour posttransfusion survival value for nontreated baboon red cells was 90% and the T50 value was 14 days. The IHP-ATP-PEG-treated red cells had significantly higher red cell ATP levels than did IHP-PEG-treated red cells. The 24-hour posttransfusion survival value was 68% for the IHP-ATP-PEG treated red cells and 52% for the IHP-PEG-treated red cells when the increase in P50 ranged from 10 to 20 mm Hg; the lifespan T50 value for both the IHP-ATP-PEG-treated red cells and the IHP-PEG-treated red cells was 15 days. Osmotic pulse treatment produced significant red cell injury manifested by the 24-hour posttransfusion survival value. However, modification of the RBC with IHP-PEG or IHP-ATP-PEG to decrease hemoglobin affinity for oxygen did not affect their lifespan.

Adenosine Triphosphate↗
PubMed1987

Electron spin resonance (ESR) studies of skeletal protein interactions in human erythrocyte membranes exposed to polyanions and in membranes prepared from inositol hexaphosphate (IHP)-incorporated low-affinity erythrocytes.

Previous biophysical investigations, including those from our laboratories, have reported that polyphosphates weaken RBC membrane skeletal protein-protein interactions and decrease hemoglobin affinity for oxygen. We have additionally demonstrated that low-affinity intact RBC's may be produced by inositol hexaphosphate (IHP) incorporation via an osmotic pulse method. In the present electron spin resonance (ESR) study, IHP was shown to cause a concentration-dependent increase in the segmental motion of ghost membrane skeletal proteins, but no alterations in spin-labeled terminal sialic acid. Pyrophosphate and inositol hexasulfate were significantly less effective in altering the physical state of skeletal proteins than was IHP. Additional ESR studies of both the interaction of IHP with membrane skeletal proteins in the presence of hemoglobin and of membranes obtained from osmotic pulse-treated intact cells were performed. The results of all these studies are discussed in terms of previous biophysical investigations of the effects of polyphosphates on membranes and of possible molecular events that occur during the osmotic pulse procedure.

2,3-Diphosphoglycerate↗
PubMed1987

Fractures about the interphalangeal joints in children.

Fracture patterns in 87 interphalangeal joint fractures in children's hands were studied and correlated with unique anatomic features of these joints. The collateral ligaments, which extend beyond the physis into the metaphysis, were found to protect the growth plate in the frontal plane. With laterally directed forces, fractures on the proximal side of the joint occurred, rather than epiphyseal fractures. There was good remodeling of angular deformities in the sagittal plane, but minimal correction in the frontal plane. In those patients treated surgically, angular deformities did not result. Of 24 condylar fractures followed for an average of 55 months, 11 (46%) demonstrated some restriction of joint motion.

Adolescent↗
PubMed1986

Effect of inositol hexaphosphate on the transient behavior of red cells following a DMSO-induced osmotic pulse.

An osmotic pulse can be used to incorporate inositol hexaphosphate (IHP) into red cells. The pulse is induced by equilibrating a red cell suspension with DMSO and then rapidly diluting with an isotonic IHP solution. Since IHP binds to hemoglobin and lowers the affinity for oxygen, this method may find application in the preparation of low-affinity cells for experimental and clinical use. The experiments reported here examined the dynamic changes of several red cell variables immediately following the osmotic pulse. The effect of IHP, which has been shown to dissociate red cell cytoskeletons, was evaluated by comparison with a matched phosphate-buffered saline (PBS) diluent. Red cell morphology, volume, and hemoglobin permeability were studied by fixing the cells at times ranging from 0.06 to 300 sec after dilution. Mechanical fragility was measured by subjecting the cells to a short period of shear stress at the same times after dilution. With both diluents, the cells underwent a rapid increase in volume followed by a return towards normal volume with a maximum at less than 250 msec. With IHP diluent, the period of hemoglobin permeability immediately followed the size peak and was completed by about 1 sec after dilution. PBS also induced a second leakage at longer times (10-120 sec), which resulted in a morphological dichotomy with ghosts and intact cells. The choice of diluent also affected sensitivity to shear stress. The IHP-treated cells had a mechanical fragility maximum at about 1 sec. The PBS-treated cells exhibited no enhanced mechanical fragility. An unexpected result was the inhibition of the second phase of lysis in PBS-treated cells by a properly timed shear stress.

Cell Membrane Permeability↗
PubMed1984

Preparation of low-affinity red cells with dimethylsulfoxide-mediated inositol hexaphosphate incorporation: hemoglobin and ATP recovery using a continuous-flow method.

Incorporation of IHP into red cells decreases oxygen affinity as a result of the binding of this compound to the 2,3-DPG site of hemoglobin. This investigation describes a continuous-flow method which utilizes the osmotic pulse technique to transport IHP into RBC. Using this procedure, it is possible to obtain a significant increase in P50 while maintaining in vitro cellular integrity. For example, IHP incorporation sufficient to cause an increase in the P50 of 20 mm Hg may be achieved with recovery of approximately 75% of the hemoglobin and with maintenance of ATP levels compatible with good viability. The continuous-flow method allows uniform treatment of large, unit-size volumes of red cells with a relatively small quantity of reagents. The final cell product is macrocytic/hypochromic with an increased number of stomatocytes.

Adenosine Triphosphate↗
PubMed1983

Incorporation of inositol hexaphosphate into red blood cells mediated by dimethyl sulfoxide.

Inositol hexaphosphate (IHP) binds to deoxyhemoglobin and markedly decreases the affinity of hemoglobin for oxygen. We introduce here a method for incorporating this polyphosphate into erythrocytes, thus preparing very low affinity cells for use in respiration research. The method uses dimethyl sulfoxide (DMSO) to facilitate entry of IHP. The cells are exposed to a high concentration of DMSO which is rapidly diluted with IHP solution. During this dilution the cells become leaky and IHP enters. The influence of several variables at each step of the process has been investigated and the data support a transient osmotic gradient mechanism for IHP incorporation.

Dimethyl Sulfoxide↗
PubMed1982

Sickling as a function of oxygen delivery: effect of simulated transfusions of stored, fresh and inositol-hexaphosphate-loaded (low affinity) red cells.

Low oxygen affinity red cells were prepared by incorporating inositol hexaphosphate (IHP) into red blood cells (rbc) by means of a liposomal transport system. The effect of in vitro simulated exchange transfusions on sickling was studied with buffered red cell suspensions containing 50% SS cells and 50% test cells. Test rbc were either stored cells with high oxygen affinity, fresh cells with normal affinity or IHP-loaded cells with decreased affinity. Oxygen equilibrium curves and percentage sickling as a function of PO2 were determined and the data analyzed in terms of percentage sickling as a function of oxygen delivery. Our simplified analysis shows that simulated exchange transfusion with stored and, to a lesser extent even with fresh blood, results in a decreased venous PO2 and increased sickling of the remaining SS cells. In contrast, transfusion with IHP-loaded cells results in higher venous PO2 values and less sickling throughout the range of oxygen delivery. Thus, the transfusion of IHP-loaded cells may result in less sickling of the remaining SS cells in addition to the normal dilutional effect.

2,3-Diphosphoglycerate↗
PubMed1981

Activation and partial characterization of a human reticulocyte heme-dependent eIF-Z alpha kinase.

An inhibitor of globin translation initiation that is activated under heme-deficient conditions and whose activity is associated with phosphorylation of the 38,000 dalton (alpha) subunit of the initiation factor eIF-2 has been previously described in rabbit reticulocytes. We describe here an analogous enzyme in human reticulocytes. The human enzyme can be activated in intact reticulocytes under conditions of heme synthesis inhibition or by incubation of lysates in the absence of hemin. Addition of hemin to lysates prevents activation of the eIF-2 alpha kinase. The partially purified kinase is associated with inhibition of globin synthesis in a rabbit cell-free system and phosphorylates the small subunit of highly purified rabbit eIF-2. We conclude that human reticulocytes contain a protein kinase that is analogous to the rabbit HCR and that may play a role in clinical heme deficiency states. l

Enzyme Activation↗
PubMed1979

The effect of INH-inhibited heme synthesis on globin synthesis.

In the rabbit reticulocyte cell-free system, optimal globin synthesis is dependent upon an adequate level of heme. The effect of heme is mediated by an inhibitor of globin synthesis initiation termed HCR. In addition to marked inhibition of total globin synthesis, HCR results in a decreased alpha/beta globulin synthesis ratio. We describe here the use of INH as a relatively nontoxic inhibitor of heme synthesis in intact rabbit reticulocytes with a resultant inhibition of globin synthesis. In parallel with the inhibition of globin synthesis in reticulocytes, an inhibitor of globin synthesis in the hemin-supplemented cell-free system is generated. No INH-induced alterations in alpha/beta synthesis ratio could be found in "stress" reticulocytes from phenylhydrazine-treated rabbits, but "normal" reticulocytes from untreated rabbits showed a decreased alpha/beta ratio. Inhibition of heme synthesis and the resulting decrease in globin synthesis and intracellular hemoglobin concentration may have application as a potential treatment of homozygous sickle cell disease.

Animals↗
PubMed1978

Asynchronous globin chain synthesis in rabbit reticulocyte lystates induced by hemin-controlled repressor.

To define further the role of hemin-controlled repressor (HCR) in globin synthesis, we studied its effect on the synthesis of individual globin chains in a rabbit reticulocyte lysate cell-free system. In the presence of HCR there was a marked globin chain imbalance, resulting in a lowered alpha/beta ratio. These findings in vitro may have relevance to certain clinical heme deficiency states in which a similar globin chain imbalance has been observed.

Animals↗
PubMed1976

Scleromyxedema.

An unusual, nodulocystic form of scleromyxedema (lichen myxedematosus) developed in a 48-year-old man with a six-year history of psoriasis. The scleromyxedema responded to intermittent therapy with melphalan and prednisone. Dermabrasion smoothed and softened the skin and increased the mobility of the perioral skin. Two months after remission of the skin lesions, psoriasis recurred.

Dermabrasion↗
PubMedDate not supplied

Amino acid requirements of a rat sarcoma as determined by a stem cell assay.

Knowledge of the amino acid requirements of a neoplasm is valuable in determining optimal nutritional support and antineoplastic therapy for the tumor-bearing host. The standard human tumor stem cell assay (HTSCA) was modified by reducing an individual amino acid below the normal plasma concentration of the Fischer 344 rat. All other amino acids were maintained at levels sufficient for normal HTSCA tumor colony growth. Twenty-two amino acids were tested at a mean concentration of 12% (range 3% to 35%) of their normal plasma level. Results indicated that all amino acids except L-glutamine and L-asparagine were present in sufficient quantity for normal tumor growth. Dose-response curves have shown more than 70% inhibition of tumor growth with a glutamine concentration of 50% and an asparagine concentration of 25%. Glutamine and asparagine levels of 4% and 1%, respectively, resulted in 100% inhibition. The data indicate that rat sarcoma stem cells are sensitive to decreased glutamine and asparagine concentrations.

Amino Acids↗