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Biomedical subjects

R S Frank

Publications and source records attributed to R S Frank.

18 recordsLinked to original sources
PubMed1999

Immunization of dogs and cats with a DNA vaccine against rabies virus.

The applicability of DNA immunization technology for vaccine development in companion animals was investigated by immunizing dogs and cats by the intramuscular (i.m.) and intradermal (i.d.) routes with a plasmid DNA vector encoding the rabies virus glycoprotein G. In dogs, administration of 100 microg DNA doses by the i.m. route resulted in stronger and more durable rabies virus neutralizing antibody (RVNA) titers than those obtained by i.d. inoculation. In contrast, i.m. vaccination of cats with a similar dose was less effective in terms of mean titer and seroconversion frequency. However, efficacy was improved by increasing the dosage to 300 microg of DNA per immunization. Interestingly, i.d. inoculation of cats appeared to be a superior route of delivery in this species, resulting in higher seroconversion frequency than i.m. administration. In addition, geometric mean RVNA titers in i.d. inoculated cats increased over four-fold during a seven month period following a second and final immunization. These results demonstrate that non-facilitated, naked DNA vaccines can elicit strong, antigen-specific immune responses in dogs and cats, and DNA immunization may be a useful tool for future development of novel vaccines for these species.

Animals↗
PubMed1998

Dirofilaria immitis: molecular cloning and expression of a cDNA encoding a selenium-independent secreted glutathione peroxidase.

A cDNA clone, Di29, encoding a homolog of glutathione peroxidase, was isolated from a Dirofilaria immitis adult female cDNA expression library by a combination of polymerase chain reaction amplification with primers designed from the Brugia pahangi glutathione peroxidase gene sequence and hybridization screening of D. immitis cDNA libraries. The Di29 nucleotide and deduced amino acid sequences were very similar to those described for lymphatic filariae and predicted a secreted form of glutathione peroxidase with a cysteine residue substituted for selenocysteine in the active site. The cDNA clone was expressed in Escherichia coli and Spodoptera frugiperda Sf9 insect cells, and the resulting recombinant proteins were purified for antibody production and assessment of enzymatic properties, respectively. An antiserum generated against the E. coli-expressed protein detected a protein of 29 kDa in D. immitis via immunoblotting. This protein is expressed in adult worms (both sexes) and fourth stage larvae generated via 6 days of in vitro culture, but was undetectable in microfilariae, and third stage larvae obtained either directly from mosquitoes or following 2 days of culture. The Di29-encoded recombinant protein was secreted from Sf9 insect cells and displayed low-level glutathione peroxidase activity against a range of hydroperoxide substrates, including hydrogen peroxide.

Amino Acid Sequence↗
PubMed1994

Passive mechanical behavior of human neutrophils: effect of cytochalasin B.

Actin is a ubiquitous protein in eukaryotic cells. It plays a major role in cell motility and in the maintenance and control of cell shape. In this article, we intend to address the contribution of actin to the passive mechanical properties of human neutrophils. As a framework for assessing this contribution, the neutrophil is modeled as a simple viscous fluid drop with a constant cortical ("surface") tension. The reagent cytochalasin B (CTB) was used to disrupt the F-actin structure, and the neutrophil cortical tension and cytoplasmic viscosity were evaluated by single-cell micropipette aspiration. The cortical tension was calculated by simple force balance, and the viscosity was calculated according to a numerical analysis of the cell entry into the micropipette. CTB reduced the cell cortical tension in a dose-dependent fashion: by 19% at a concentration of 3 microM and by 49% at 30 microM. CTB also reduced the cytoplasmic viscosity by approximately -25% at a concentration of 3 microM and by approximately 65% at a concentration of 30 microM when compared at the same aspiration pressures. All three groups of neutrophils, normal cells, and cells treated with either 3 or 30 microM CTB, exhibited non-Newtonian behavior, in that the apparent viscosity decreased with increasing shear rate. The dependence of the cytoplasmic viscosity on deformation rate can be described empirically by mu = mu c(gamma m/gamma c)-b, where mu is cytoplasmic viscosity, gamma m is mean shear rate, mu c is the characteristic viscosity at the characteristic shear rate gamma c, and b is a material coefficient. The shear rate dependence of the cytoplasmic viscosity was reduced by CTB treatment. This is reflected by the changes in the material coefficients. When gamma c was set to 1 s-1, pc = 130 +/- 23 Pa.s and b = 0.52 +/- 0.09 for normal neutrophils and pc = 54 +/- 15 Pa.S and b = 0.26 +/- 0.05 for cells treated with 30 micro M CTB. These results provide the first quantitative assessment of the role that Pa-s-actin structure plays in the passive mechanical properties of human neutrophils.

Actins↗
PubMed1993

Ischemia with intermittent reperfusion reduces functional and morphologic damage following renal ischemia in the rat.

Attempts to minimize ischemic injury by interrupting a given ischemic period might be compromised if repeated bouts of reperfusion injury occurred. To determine whether intermittent ischemia improved or worsened functional and morphologic outcome of renal ischemia, halothane-anesthetized rats underwent a right nephrectomy and placement of a snare about the left renal vascular pedicle at 37 degrees C. Eleven animals underwent 45 minutes of continuous renal ischemia (C-ISC), whereas 10 animals received 45 minutes of vessel occlusion interrupted (I-ISC) at 15 and 30 minutes by snare release and 5 minutes of reperfusion. A group of three sham rats underwent the above procedure but did not have the snare tightened. Blood samples were drawn preoperatively and 24, 48, and 72 hours postoperatively for creatinine analysis. At 72 hours the animals were sacrificed and their kidneys morphologically evaluated. The C-ISC group had a significantly higher mean postoperative plasma creatinine (p < 0.01) as well as significantly higher plasma creatinine levels at 24 (p < 0.005) and 48 hours (p < 0.05) than did the I-ISC group. The C-ISC group also demonstrated significantly greater histologic damage than the I-ISC group (p < 0.002) when assessed by a pathologist blinded to the intervention. Sham rats did not demonstrate functional or morphologic damage. These data demonstrate a significantly improved outcome when 45 minutes of renal ischemia is interrupted by periods of reperfusion. We are led to conclude that in this setting reperfusion injury did not overwhelm the salutary effects of interrupting the 45-minute ischemic event.

Animals↗
PubMed1993

Passive mechanical behavior of human neutrophils: power-law fluid.

The mechanical behavior of the neutrophil plays an important role in both the microcirculation and the immune system. Several laboratories in the past have developed mechanical models to describe different aspects of neutrophil deformability. In this study, the passive mechanical properties of normal human neutrophils have been further characterized. The cellular mechanical properties were assessed by single cell micropipette aspiration at fixed aspiration pressures. A numerical simulation was developed to interpret the experiments in terms of cell mechanical properties based on the Newtonian liquid drop model (Yeung and Evans, Biophys. J., 56: 139-149, 1989). The cytoplasmic viscosity was determined as a function of the ratio of the initial cell size to the pipette radius, the cortical tension, aspiration pressure, and the whole cell aspiration time. The cortical tension of passive neutrophils was measured to be about 2.7 x 10(-5) N/m. The apparent viscosity of neutrophil cytoplasm was found to depend on aspiration pressure, and ranged from approximately 500 Pa.s at an aspiration pressure of 98 Pa (1.0 cm H2O) to approximately 50 Pa.s at 882 Pa (9.0 cm H2O) when tested with a 4.0-micron pipette. These data provide the first documentation that the neutrophil cytoplasm exhibits non-Newtonian behavior. To further characterize the non-Newtonian behavior of human neutrophils, a mean shear rate gamma m was estimated based on the numerical simulation. The apparent cytoplasmic viscosity appears to decrease as the mean shear rate increases. The dependence of cytoplasmic viscosity on the mean shear rate can be approximated as a power-law relationship described by mu = mu c(gamma m/gamma c)-b, where mu is the cytoplasmic viscosity, gamma m is the mean shear rate, mu c is the characteristic viscosity at characteristic shear rate gamma c, and b is a material coefficient. When gamma c was set to 1 s-1, the material coefficients for passive neutrophils were determined to be mu c = 130 +/- 23 Pa.s and b = 0.52 +/- 0.09 for normal neutrophils. The power-law approximation has a remarkable ability to reconcile discrepancies among published values of the cytoplasmic viscosity measured using different techniques, even though these values differ by nearly two orders of magnitude. Thus, the power-law fluid model is a promising candidate for describing the passive mechanical behavior of human neutrophils in large deformation. It can also account for some discrepancies between cellular behavior in single-cell micromechanical experiments and predictions based on the assumption that the cytoplasm is a simple Newtonian fluid.

Biomechanical Phenomena↗
PubMed1992

Minimal physiologic temperature variations during renal ischemia alter functional and morphologic outcome.

Aortic and renal vascular reconstruction often involve significant renal ischemia. Profound hypothermia during renal ischemia preserves renal tissue. However, in the clinical setting of vascular reconstruction specific attempts at cooling the kidney are often impractical, and renal ischemia frequently occurs at physiologic temperatures. This study demonstrates that minimal temperature changes during renal ischemia alter the functional and morphologic outcome. Rats anesthetized with halothane underwent a right nephrectomy and placement of a snare around the left renal pedicle for 45 minutes to produce renal ischemia. Seventy-five adult male Sprague-Dawley rats, weighing 250 to 350 gm were divided into three groups based on the body temperature maintained during renal ischemia (35 degrees C, 37 degrees C, 39 degrees C). Body temperature was continuously monitored with a rectal thermistor and maintained by adjustment of a heating pad and lamp. Two postischemic protocols were followed including a creatinine assessment protocol with blood samples collected at 24, 48, and 72 hours and a histologic assessment protocol with biopsy of the kidney at 30 hours. At 24 hours after ischemia plasma creatinine concentrations were increased in rats with elevated body temperatures (35 degrees C vs 37 degrees C; [p = 0.001], 37 degrees C vs 39 degrees C; [p = 0.150]). The 30-hour histologic assessment indicated a difference in morphologic outcome (35 degrees C vs 37 degrees C; [p = 0.063], 37 degrees C vs 39 degrees C; [p = 0.016]), with proximal tubular morphology being better maintained at lower temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Time-dependent alterations in the deformability of human neutrophils in response to chemotactic activation.

Transit times of individual human neutrophils through single capillary-sized pores were measured to determine the time-dependent changes in the mechanical behavior of the cells during activation by the chemotactic agent formyl-methionyl-leucyl-phenylalanine (FMLP) and in response to cytochalasin B (CTB) and colchicine. FMLP elicited a two-phase response consisting of a rapid increase in cell stiffness, which peaked between 2 and 3 minutes, followed by a partial recovery of deformability to a level significantly above that of control after 5 minutes. The mechanical changes closely followed changes in F-actin content, although the peak in cell stiffness appeared to lag the F-actin response. Treatment with 3 mumols/L CTB produced a transient decrease in cell rigidity followed by a return to control level in 10 minutes, whereas treatment with 30 mumols/L CTB resulted in a sustained decrease in cell transit times to a level 60% of control. Addition of 3 mumols/L CTB to cells prestimulated with FMLP produced a rapid (1 to 2 minutes) cessation of changes in cellular deformability produced by the FMLP. Colchicine treatment did not decrease cell rigidity, but produced a delayed increase in F-actin content accompanied by increased stiffness of the cells. These results implicate actin as the major determinant of the mechanical behavior of the neutrophil, as measured by whole cell deformability tests. The significant changes in cell deformability that occur in response to fractional changes in F-actin content suggest that changes in the structure of the actin network occur during these processes.

Actins↗
PubMed1990

The behavior of human neutrophils during flow through capillary pores.

The passage times of individual human neutrophils through single capillary-sized pores in polycarbonate membranes were measured with the resistive pulse technique, and results were compared to those obtained from the micropipette aspiration of entire cells. Pore transit measurement serves as a useful means to screen populations of cells, and allows for protocols that measure time dependent changes to the population. Neutrophils exhibited a highly linear pressure/flow rate relationship at aspiration pressures from 200 Pa to 1,500 Pa in both the pore and pipette systems. Cellular viscosity, as determined by the method of Hochmuth and Needham, was 89.0 Pa.s for the pore systems and 134.9 Pa.s for the pipette systems. These results are in general agreement with recent values of neutrophil viscosity published in the literature. Extrapolation of the observed linear flow response revealed an apparent minimum pressure for whole cell aspiration significantly above the threshold pressure predicted by Evans' liquid drop model. However, whole cell aspiration was achieved in both the pore and pipette systems at pressures below this extrapolated minimum, although the calculated cellular viscosity was greatly increased. The implications of these two regimes of cell deformation is unclear. This behavior could be explained by shear thinning of the material in the cell body. However the origin of this phenomenon may be in the cortical region of the cell, which exhibits an elastic tension that may be deformation rate dependent.

Adult↗
PubMed1988

The influence of red cell mechanical properties on flow through single capillary-sized pores.

The resistive pulse technique was used to study the influence of specific mechanical properties of the red cell on its ability to enter and flow through single capillary-sized pores with diameters of 3.6, 5.0 and 6.3 micron and lengths of 11 micron. A two-fold increase in membrane shear elasticity resulted in a 40 percent increase in the cell's transit time through a 3.6 micron pore but produced no change in transit time through a 6.3 micron pore. A two-fold increase in membrane shear viscosity produced a 40 percent increase in transit time through the 3.6 micron pore and small but significant increases in transit times through the larger pores. Osmotically dehydrated cells showed no increase in transit time through a 6.3 micron pore, but showed increases in transit times of 50 to 70 percent through 5.0 and 3.6 micron pores. Dense red cells showed increased transit times through both 5.0 micron and 6.0 micron pores. These results indicate that for cells with normal geometric properties, the membrane's shear viscosity and elasticity only influence the cell's transit through pores of 5 micron or less in diameter. However, alterations in the cell's geometric properties can extend the influence of membrane shear properties to larger diameter pores.

Adult↗
PubMed1988

Renal vasoconstriction and transient declamp hypotension after infrarenal aortic occlusion: role of plasma purine degradation products.

To better understand renal and systemic hemodynamics associated with hindquarter ischemia produced by aortic compression, chloralose-anesthetized dogs were given phentolamine while an external clamp maintained infrarenal aortic pressure below 25 mm Hg for 45 minutes. In four sham-operated dogs, infrarenal pressure was maintained; reinforced cannulas, capable of resisting clamp compression, were placed within the aorta and the inferior vena cava. Suprarenal and infrarenal arterial pressure and renal blood flow were continuously monitored. Blood samples taken before clamp application and at 1, 3, 5, and 10 minutes after clamp removal were assayed for adenosine, inosine, xanthine, and hypoxanthine. On clamp removal suprarenal pressure immediately dropped from a preclamp pressure of 114 to 82 mm Hg but returned to preclamp values within 1 minute. Renal blood flow was significantly reduced after clamp release, reaching a nadir of 39% of preclamp flow. This reduction persisted despite a normalization of arterial pressure. Summed plasma purines were significantly elevated 1 minute after clamp removal. Sham-operated dogs showed no significant alterations in arterial pressure, renal blood flow, or plasma purine levels. This study demonstrates a significant non-alpha-adrenergic receptor-mediated reduction in renal blood flow and a coincident increase in purine degradation products after removal of an infrarenal aortic cross-clamp.

Adenosine↗
PubMed1987

An investigation of particle flow through capillary models with the resistive pulse technique.

The use of the resistive pulse technique for the measurement of microsphere and red cell transit times through single-pore "Nuclepore" membranes (with pore diameters of 3.5 to 7.0 microns and pore length of approximately 11 microns) is described. The investigation of the fluid mechanics and electrical characteristics of the experimental system provides methods for the determination of particle and cell size, and entrance and transit times. Experimental measurement of the position dependent velocity of spherical particles through the pore shows close agreement with theoretical models. Red cell size and transit time through different sized pores at physiological shear stresses is also measured.

Blood Flow Velocity↗
PubMed1986

Morphometric evaluation of brain infarcts in rats and gerbils.

The Levine rat preparation, the gerbil stroke model, and appropriate control animals were used to determine if the 2,3,5-triphenyltetrazolium chloride (TTC) would selectively identify noninfarcted versus infarcted cerebral tissue. The TTC is frequently used to quantify infarcted myocardial tissue and has been shown to have great specificity, reproducibility, and efficacy. The TTC produces a red product upon reaction with the respiratory enzymes (dehydrogenases) present in non-infarcted tissues. Irreversibly damaged tissues, lacking dehydrogenases, do not form red reaction products. Six gerbil brains and seven rat brains were incubated with the TTC, and the unreacted areas were macroscopically identified. The brains were fixed and sectioned for routine hematoxylin and eosin staining to determine the specificity of the TTC. The TTC was found to react selectively only with non-infarcted cerebral tissue. The gross brain sections were evaluated by macroscopic morphometric analysis, and the unreacted area was always ipsilateral to ligation and correlated with histologic identification of infarct. The brains from neurologically intact animals demonstrated neither macroscopic nor histological evidence of infarction. This technique allows macroscopic quantification of infarct size by planimetry. The average area of infarct for the neurologically impaired rats was 34.7% and it was 31.4% for the impaired gerbils. The percentage of surface area of each infarcted slice was found to correlate with the severity of the neurologic deficit. We conclude that TTC staining is effective for macroscopically delineating cerebral infarcts in rats and gerbils, thus permitting quantification of infarct size.

Animals↗
PubMed1983

The clandestine drug laboratory situation in the United States.

Clandestine, or illegal, laboratories are operated by the criminal element to circumvent legal requirements with the goal of supplying drugs of abuse to the illicit market. Investigation of clandestine drug manufacturing laboratories is a high priority of the U.S. Drug Enforcement Administration (DEA) because elimination of these laboratories will prevent drugs of abuse from reaching the illicit drug traffic. One of the important responsibilities of forensic chemists assisting in investigations of clandestine drug laboratories is to be familiar with the methods of synthesis being used by clandestine laboratory operators. A review of clandestine laboratory seizures during the period of 1978 through 1981 will be provided to familiarize forensic chemists with current information on the types of laboratories being seized in the United States and the methods of synthesis being used.

3,4-Methylenedioxyamphetamine↗
PubMed1980

Vasodilator and constrictor responses to hypoxia in isolated pig lungs.

We examined transient and steady-state responses of the pulmonary circulation to hypoxia in isolated pig lungs perfused with autologous blood. Responses were quantified by the pulmonary artery pressure at a flow of 1 l/min (Ppa1) read directly from pressure-flow recordings. Alveolar carbon dioxide tension was constant at 38 Torr and alveolar oxygen pressure (PAO2) was varied between 670 and 0 Torr. When PAO2 was lowered progressively every 10 min, the relation between PAO2 and Ppa1 was sigmoidal, with maximum constriction occurring at a PAO2 of 0 Torr; however, if Ppa1 was allowed to reach a steady state at each level of PAO2, the relation was reproducibly and reversibly biphasic. Ppa1 increased as PAO2 decreased from 670 to 60 Torr, was maximum and stable at PAO2 between 60 and 30 Torr, and decreased as PAO2 was lowered from 30 to 0 Torr. As a result, steady-state Ppa1 at PAO2 greater than or equal to 200 Torr was similar to that at PAO2 = 0 Torr. When PAO2 was changed from 200 Torr to a constant lower level, Ppa1 required 20-30 min to achieve a steady state at PAO2 greater than or equal to 25 Torr and 40-50 min at PAO2 of 10 and 0 Torr. With the latter, the responses consisted of vasoconstriction followed by marked vasodilation. Thus pulmonary vasomotor tone was a complex function of both PAO2 and time. Attempts to explain the pulmonary vascular response to hypoxia must take these complexities into account.

Animals↗
PubMedDate not supplied

Drugs of abuse: data collection systems of DEA and recent trends.

The U.S. Drug Enforcement Administration has several different systems for collecting information on drugs of abuse. One is an early warning system, which collects information to provide scientific data and interpretation on drug abuse. Another is the collection of data from evidence submitted to DEA laboratories. This is a review of the significance of the data in each system and an examination of some of the trends observed from the data.

Costs and Cost Analysis↗
PubMedDate not supplied

Changes in mechanical properties with DMSO-induced differentiation of HL-60 cells.

We measured changes in the deformability of human promyelocytic leukemic (HL-60) cells induced to differentiate for 5-6 days along the granulocyte pathway by 1.25% dimethylsulfoxide (DMSO). Differentiation resulted in an approximately 90% reduction in the transit times of the cells through capillary-sized pores over a range of aspiration pressures. Cell volume, as measured by two methods, decreased by an average of 35%. To account for the contribution of the volume decrease to the decrease in transit time, the liquid drop model, developed to describe neutrophil deformability, was used to calculate an apparent viscosity of the cells during this deformation. The apparent viscosity of both uninduced and induced HL-60 cells was a function of aspiration pressure, and an approximately 80% reduction in viscosity occurred with induction, as determined by regression analysis. The deformation rate-dependent viscosities of the induced cells were between 65 and 240 Pa-sec, values similar to those measured for circulating neutrophils. To assess the role of polymerized actin in these viscosity changes, intracellular F-actin content was measured, and the effect of dihydrocytochalasin B (DHB), an agent that disrupts actin polymerization, was determined. Despite the significant decrease in cellular viscosity, F-actin content per cell volume did not change significantly after induced differentiation. Treatment with 3 and 30 microM DHB lowered cellular F-actin content in a dose-dependent manner in both uninduced and induced cells. Cellular viscosity of both uninduced and induced cells decreased sharply with 3 microM DHB treatment (85% and 76% respectively). 30 microM DHB treatment caused a further significant reduction in the viscosity of uninduced cells, but for induced cells the additional decrease in viscosity was not significant. These data indicate that reductions in both cell volume and intrinsic viscosity contribute to the increased deformability of HL-60 cells with DMSO-induced differentiation. However, changes in the concentration of F-actin cannot account for the decrease in cellular viscosity that occurs.

Actins↗