Functional analysis of a cytoplasmic domain-deleted mutant of the CD4 molecule

The CD4 molecule is a receptor found on a subset of T lymphocytes. It has been proposed that, upon binding MHC class II molecules expressed on APC, the CD4 molecule enhances the responsiveness of the T cell by increasing intercellular avidity and/or by transducing an intracellular signal. We have analyzed the effect of removing the cytoplasmic domain of the CD4 molecule on the ability of the CD4 molecule to enhance T cell responsiveness. The cytoplasmic domain-deleted mutant of the CD4 molecule (CD4 delta) was found to be as efficient as the CD4 molecule at enhancing responsiveness to cells bearing the appropriate Ag. If subcellular Ag in the form of purified Ag incorporated into liposomes was used, the CD4 molecule was found to be much more efficient than the CD4 delta molecule at enhancing responsiveness. However, the defect in the ability of the CD4 delta molecule to enhance responsiveness could be compensated for by increasing the level of expression of the CD4 delta molecule.

Genetic analysis of monoclonal antibody and HIV binding sites on the human lymphocyte antigen CD4

Saturation mutagenesis and a complement fixation selection have yielded CD4 point mutants with impaired antibody and human immunodeficiency virus binding. The patterns of amino acid substitution, in conjunction with previous antibody cross-blocking data, affirm the similar tertiary structures of the CD4 amino-terminal domain and immunoglobulin variable regions. Single residue substitutions affecting virus binding and syncytium formation are observed over an eight residue segment located in a portion of the molecule homologous to the second hypervariable region of an antibody combining site.

Expression of the T-cell surface molecule CD2 and an epitope-loss CD2 mutant to define the role of lymphocyte function-associated antigen 3 (LFA-3) in T-cell activation

To define the role of the CD2-lymphocyte function-associated antigen 3 (LFA-3) interaction in T-cell activation, we have expressed a cDNA encoding the human CD2 molecule in a murine antigen-specific T-cell hybridoma. Expression of the CD2 molecule greatly enhances T-cell responsiveness to antigen; this enhancement is inhibited by anti-CD2 and anti-LFA-3 monoclonal antibodies (mAbs). CD2+ hybridomas produce interleukin 2 in response to combinations of anti-CD2 mAbs 9.6 and 9-1 and, in the presence of mAb 9-1, to sheep erythrocytes or to the LFA-3 antigen. Furthermore, hybridomas expressing a mutant CD2 molecule that has lost mAb 9.6 binding do not exhibit the enhanced response to antigen or the ability to respond to LFA-3 plus mAb 9-1, but these hybridomas retain the ability to respond to combinations of anti-CD2 mAbs. The role of the CD2-LFA-3 interaction in T-cell activation and the potential for other physiologic ligands for CD2 are discussed.

Immunohistochemical identification of quinolinic acid phosphoribosyltransferase in glial cultures from rat brain

Glial cell cultures were shown to contain 3 identifiable classes of cells which could be specifically stained with antibodies directed against quinolinic acid phosphoribosyltransferase (QPRT), the catabolic enzyme of the endogenous excitotoxin quinolinic acid. Some, but not all, QPRT-positive cells also contained glial fibrillary acidic protein. These cultures may constitute an in vitro system in which cerebral quinolinic acid metabolism and function can be examined.

Expression and assembly of a human neurofilament protein in transgenic mice provide a novel neuronal marking system

To investigate the regulation of neurofilament gene expression, we have generated several lines of transgenic mice carrying multiple copies of a cloned human neurofilament (NF-L) gene. We show that a 21.5-kb DNA fragment including the human NF-L gene contains essential information for correct expression in nervous tissue of transgenic mice. The integrated genes are arranged in multiple tandem arrays, but the extent of transgene expression does not correlate with copy number nor does it influence the expression of the endogenous neurofilament genes. However, the levels of human NF-L protein recovered in neurofilament preparations from brains of transgenic mice correlate directly with the relative abundance of human NF-L mRNA detected in each line. There is an apparent delay in the accumulation of human NF-L protein during development, as determined by immunoblotting with a human-specific monoclonal antibody. Finally, immunohistochemical localization of the human NF-L protein results in the specific staining of neurons and their processes in transgenic mice.

Expression and function of CD8 in a murine T cell hybridoma

In general, the human CD8 molecule is expressed on T cells specific for HLA class I molecules. Studies designed to delineate the function and to define the ligand of the CD8 molecule have been complicated by the fact that the presumptive ligand for CD8 is on the HLA class I molecule, the same molecule encoding the ligand for the antigen-specific T cell receptor. The ability to express genes in cells other than their natural host has produced a new technology with which to approach CD8 functional studies. The insertion of a cDNA clone for CD8 in a defective retroviral vector has allowed the transfer of CD8 by infection with the resulting defective retrovirus. CD8 was then expressed in an HLA class II-specific T cell, thus separating the ligand requirements of the TCR and CD8. By this approach, the human CD8 molecule was expressed in a murine T cell hybridoma specific for human class II antigens. The resulting CD8+ hybridomas demonstrated a 10-fold increase in IL-2 production over the parent cell line when stimulated with JY, a human B lymphoblastoid cell line expressing both class I and II HLA antigens, demonstrating that expression of CD8 increases T cell activation. mAbs directed against the CD8 molecule inhibited the response of CD8+ hybridomas to JY, supporting the conclusion that the CD8 molecule was fractional. The role of CD8 as a receptor for class I MHC antigens was addressed by stimulation with a cell line expressing HLA-DR antigens, but lacking the expression of HLA class I antigens (Daudi). Stimulation of the CD8+ hybridomas by Daudi did not result in increased IL-2 production. The response to Daudi was unaltered by the addition of anti-CD8 mAb, in contrast to the ability of anti-CD8 mAb to block JY stimulation. Furthermore, mAbs directed against the class I antigens present on JY cells were able to block the enhanced response of the CD8+ hybridomas to JY. These data support the hypothesis that HLA class I molecules are the ligands involved in the CD8-dependent enhancement of T cell activation.

Monoclonal antibody and ligand binding sites of the T cell erythrocyte receptor (CD2)

The human T cell erythrocyte receptor (CD2 antigen) allows thymocytes and mature T cells to adhere to thymic epithelium and target cells through a cell surface protein, LFA-3 (refs 1-6). Monoclonal antibodies recognizing CD2 can either block adhesion or, in certain combinations, induce an antigen-independent T cell activation. We have identified the binding sites for 16 monoclonal antibodies against CD2 by a rapid and generally applicable mutational analysis. The binding sites fall in three discrete regions: antibodies that participate in activation and block erythrocyte adhesion bind to the first region; antibodies that block adhesion bind to the second region; and antibodies that participate in activation but do not block adhesion bind to the third region. A large number of mutations selected for loss of antibody reactivity in the first two regions also weaken the CD2-LFA-3 interaction. Good agreement was observed between mutational lesions blocking LFA-3 binding and lesions blocking binding by activating antibodies, which supports the view that such antibodies induce T cell activation by mimicking the effect of LFA-3 binding. CD2 sequences that participate in LFA-3 binding correspond to immunoglobulin variable region hypervariable sequences when the homologous domains are aligned.

Expression and function of CD4 in a murine T-cell hybridoma

The CD4 (T4) antigen was originally described as a phenotypic marker specific for helper T cells, and has recently been shown to be the receptor for the human immunodeficiency virus (HIV). Functional studies using monoclonal antibodies directed at CD4 and major histocompatibility complex (MHC) class II molecules led to the suggestion that CD4 binds to the MHC class II molecules expressed on stimulator cells, enhancing T-cell responsiveness by increasing the avidity of T cell-stimulator cell interaction and/or by transmitting a positive intracellular signal. But recent evidence that antibodies to CD4 inhibit T-cell responsiveness in the absence of any putative ligand for CD4 has been interpreted as suggesting that antibody-mediated inhibition may involve the transmission of a negative signal via the CD4 molecule instead. We have infected a murine T-cell hybridoma that produces interleukin 2 (IL-2) in response to human class II HLA-DR antigens with a retroviral vector containing CD4 cDNA. The resulting CD4-expressing hybridoma cell lines produce 6- to 20-fold more IL-2 in response to HLA-DR antigens than control cell lines. Furthermore, when antigen levels are suboptimal, the response of the cell lines is entirely CD4-dependent. The data presented here clearly demonstrate that CD4 can enhance T-cell responsiveness and may be crucial in the response to suboptimal levels of antigen.

Depletion of T cells from bone marrow for allogeneic transplantation: method for treatment of bone marrow in bulk

T lymphocytes were depleted from donor marrow for 23 patients undergoing allogeneic bone marrow transplantation using an anti-T-cell antibody, CT-2, and complement. The methodology is described in detail for in vitro depletion of large quantities of bone marrow. The extent of T-lymphocyte depletion using various T-cell markers, the percent of marrow lost in the processing and quantity of antibody, and complement needed are presented. These techniques for in vitro T-lymphocyte depletion were reproducible and did result in an average final yield of 47% of the harvested donor marrow.

Oxidative metabolism in cultured astroglial cells from rat brain

Growth, morphology, glutamine synthetase activity, cytochrome C oxidase activity and respiratory activity of rat brain cultures enriched in astrocytes were studied during four weeks in culture. Two different polarographic methods were used for measurement of respiratory activity: one newly developed perfusion method leaving the cellular monolayer morphologically intact and still attached to the culture dish, and one traditional stirring method involving the removal of cells from the culture vessel. Regardless of the method used, a stable respiratory activity was registrated throughout the four weeks of culturing. Also the cytochrome C oxidase activity remained unchanged. In perfusion all absolute values for respiration were found to be higher than those obtained with the stirring method. The use of the stirring technique resulted in a doubling of oxygen consumption upon succinate addition. No such effect was seen in perfusion. It can thus be concluded that the removal of cultured astrocytic cells from their substratum alters their respiratory activity and their response to added substrates.

Glucosephosphate isomerase (GPI-1) expression in mouse ova: cis regulation of monomer realization

A survey of the glucosephosphate isomerase (GPI-1) activity expressed in mature mouse ova has revealed multiple interstrain differences. Genetic variation at a site either linked to (less than 1.1 cM) or directly associated with Gpi-1 affects the realization of GPI-1 monomers during the later stages of oocyte maturation.

Use of a perfusion technique for measurements of respiratory activity in cultured cells

A method for measuring respiratory activity in anchorage-dependent cultured cells has been developed. This method is based on a technique that permits the perfusion of standard plastic culture dishes with attached cells. Basal respiratory activities were studied in two continuous cell lines of neural origin, neuroblastoma C1300 clone 41A3 and glioma 138MG. As compared to traditional measurements on detached cells, a fourfold increase in value was obtained. Investigations on membrane permeability suggested that the observed difference could be attributed to alterations in cell membrane integrity. Pretreatment with dibutyryl cyclic AMP, known to induce a morphological and biochemical differentiation in C1300 and 138MG cells, caused in both cell lines an enhanced respiration.

Photometric recording of cell viability using trypan blue in perfused cell cultures

A perfusion system was developed to increase the reliability of cell viability estimations by continuous measurement of the uptake of trypan blue dye. Monolayer cell cultures were perfused with buffer containing toxic substances and trypan blue, and the staining of cells was continuously recorded at 591 nm in a spectrophotometer. Using mercuric chloride and methylmercuric chloride as test substances with C6 rat glioma cells, time- and dose-dependent increases in light absorbance were obtained over a 12h recording period. Methylmercuric chloride at 10(-6) M caused a half-maximal increase in relative absorbance in 4.5 h, whereas the corresponding time for mercuric chloride was 10.5 h.

Effects of toxic chemicals on the respiratory activity of cultured mouse neuroblastoma cells

Twenty common toxic chemicals were tested for their ability to inhibit respiratory activity in cultured mouse neuroblastoma C1300 cells, clone 41A3. Pentachlorophenol and hexachlorophene exhibited the properties of uncouplers of oxidative phosphorylation, whereas for KCN, pyridine, 2,5-hexandione, NaAsO2, K2Cr2O7, HgCl2, methylmercury and triethyltin more simple time-courses of inhibition were obtained. Ethanol, methanol, dimethyl sulphoxide, benzidine, nickel acetate, MnCl2, phenol, CoCl2, Na2SeO3 and CdCl2 did not cause any significant changes in respiratory activity. Among the effective compounds, those with well-known neurotoxic properties were the most potent in inhibiting respiration in 41A3 cells.

Effects of dissolved carbon monoxide on the respiratory activity of perfused neuronal and muscle cell cultures

In order to address the question of whether small amounts of dissolved CO may inhibit cellular respiration, cultured mouse neuroblastoma cells and primary cultures of chick neurons, rat astrocytes and chick skeletal muscle and heart cells were exposed to CO containing buffer solutions in a closed perfusion system. Oxygen uptake was measured simultaneously with two polarographic oxygen electrodes as the difference in partial pressure of oxygen between the inlet and outlet of the perfusion chamber. After registration of the basal respiratory activity, perfusion solutions containing 5 ul 02/ml were bubbled with CO or N2 at a rate of 200 ml/min for 120 sec. By this procedure the partial pressure of 02 was decreased to reach a value of about 50% of the initial 02 content for both gases. Perfusion was then continued for 30 min at a rate of 0.5 ml/min. The respiratory activity of all the perfused cell cultures, except chick neurons, was found to be inhibited (13-29%) by perfusion solutions bubbled for 120 sec with CO as compared to N2 controls. Of the cells from the nervous system, astrocytes were more sensitive than neurons. Apparently, small amounts of dissolved CO can inhibit cellular respiration in the presence of a physiologically adequate amount of oxygen.

Disease expression in +-/+- ----mdg/mdg mouse chimeras: evidence for an extramuscular component in the pathogenesis of both dysgenic abnormal diaphragm innervation and skeletal muscle 16 S acetylcholinesterase deficiency

Homozygous mdg/mdg mice die at birth and express a syndrome of abnormalities, the most striking of which is a gross failure of skeletal muscle development. Recently, additional abnormalities in the development of nerve-muscle relationships have been recognized; in particular, on muscle fibers within the diaphragm, motor end plates are inappropriately dispersed and, in all muscles, there is a paucity of the 16 S form of acetylcholinesterase (AChE). These abnormalities could result entirely as secondary consequences of the primary muscle defect or from expression of the mdg defect in additional cell types, e.g., motor neurons. To determine if the muscle genotype alone is responsible for these defects in dysgenic mice, chimeras composed of both dysgenic and normal cells have been investigated. Different glucosephosphate isomerase variants existed in the mdg/mdg and normal cells comprising these chimeras and the mutant, normal, or mosaic genotypes of chimera diaphragm and skeletal muscle was estimated by measuring the relative proportions of each isozyme. In two chimeras, the diaphragm innervation pattern was revealed by AChE cytochemistry and in both, discrete regions of abnormally dispersed and normally restricted motor end-plate zones were observed. No correlation between these patterns of innervation and the assessed genotype of the muscle fibers existing in each area was observed. The relative 16 S AChE content in the limbs of four chimeras was found to range from 2.5 to 42.0%. Here also, no correlation between 16 S AChE content and the muscle genotype was observed. The results of these investigations are not consistent with a model of mdg/mdg pathogenesis in which only the skeletal muscle is primarily affected; an extramuscular deficiency responsible for at least part of the full mdg/mdg syndrome is therefore suggested.

Neurons induce contractions in myotubes containing only muscular dysgenic nuclei

Muscular dysgenic (mdg/mdg) myotubes cultured alone do not contract. Glucosephosphate isomerase (GPI-1) isozymes were analyzed to determine the final genotype of cultured dysgenic (mdg/mdg, gpi-1a/a) myotubes to which normal embryonic spinal cord and limb cells (CBA/J +/+, gpi-1b/b) had been added. Although both myoblast and spinal cord cell additions caused induction of spontaneous contractions, only myoblasts fused with the myotubes to create functional heterokaryons. Spinal cord cells did not fuse with dysgenic myotubes, but formed functional synapses.

Relationship of genotype and in vitro contractility in mdg/mdg in equilibrium +/+ "mosaic" myotubes

Muscular dysgenesis (mdg) in the mouse is an autosomal recessive lethal disorder that is manifested by a gross failure of skeletal muscle development. In vitro mdg/mdg myoblasts proliferate normally and fuse successfully into myotubes, but these myotubes fail to contract either spontaneously or in response to physiological stimuli despite the presence of effective contractile elements and an ability to propagate action potentials normally. We have determined that mdg/mdg and +/+ myoblasts are capable of fusing in vitro to form "mosaic" myotubes which typically express an apparently normal contractile phenotype. Electrophoretic analysis of the relative activities of myotube glucosephosphate isomerase (GPI-1) isozymes provided a means of estimating the proportions of myonuclei of each genotype within individual myotubes. Only a very small proportion of genotypically normal myonuclei were required for expression of an apparently normal contractile phenotype.

On the application of cultured neuroblastoma cells in chemical toxicity screening

The acute toxic action of a number of common chemicals was tested by their ability to cause detachment of cultured mouse neuroblastoma C1300 cells. A TD25 value was obtained by graphic estimation of the concentration needed to cause 25% of the total cell number to detach. These TD25 values were compared with LD50 values obtained from the literature, and they were found to correlate with a coefficient of 0.86. For six of the tested substances-diuron, butylated hydroxytoluene, benzidine, cyclophosphamide, Na2SeO3, and KCN-a very poor correlation was obtained. These diverging results could be ascribed to deficiencies in the neuroblastoma cell detachment test and emphasize the necessity for combined in vitro test procedures.

Growth and morphology of neuronal cell lines cultured in perfusion

To optimize culture conditions and gain a more reliable culturing system for studies of metabolic properties of neuronal cells, a simplified perfusion chamber was developed. It consists of two parts: a perfusion block and a standard plastic culture dish. To confirm the suitability of this chamber for continuous culturing of anchorage-dependent cells, the growth and morphology of the four neuronal cell lines, glioma C6 and glioma 138MG, neuroblastoma C1300, clones N1E115 and N18 were followed for 4 d using both traditional and perfusion techniques. A marked increase in growth and a decrease in the degree of morphological differentiation were obtained with the latter technique compared to the former.

P1 deficiency in shiverer myelin is expressed by Schwann cells in shiverer dystrophic normal mouse chimaera nerves

The myelin basic protein (P1) deficiency in shiverer myelin is expressed in shiverer reversible normal mouse chimaera nerves. Chimaera examined with immunocytochemical techniques have revealed populations of both densely labeled and unreacting myelinated Schwann cells. Single axons can innervate both Schwann cell types, demonstrating that the expression of P1 in Schwann cell myelin is unrelated to the shiverer or normal genotype of the neuron. The coexistence of both Schwann cell types in single nerves indicates that multiple progenitor Schwann cells are allocated to developing nerves and the mosaic patterns expressed further suggest that such cells tend to proliferate relatively small coherent clones of Schwann cells.

The use of electrosurgery in reconstructive and cosmetic maxillofacial surgery

The electrosurgical incision is not cutting incision but one that causes molecular dissolution along the path of the electrode. This phenomenon helps demonstrate how electrosurgery may be performed with a minimal amount of scar tissue. The atraumatic electrosurgical removal of undesirable tissue of traumatically or pathologically altered parts of the maxillofacial anatomy allows esthetic results equal to and in some cases superior to the steel scalpel. Tissue undergoing electrosurgery must be adequately hydrated for satisfactory results. The surgeon using electrosurgery must be properly trained and thoroughly familiar with electrosurgical techniques. He must also be familiar with the effects of local wound environment on healing.

Acute toxicity of organic solvents, heavy metals and DDT tested in cultures of mouse neuroblastoma cells

To test the toxicity of some substances, known to affect the nervous system i.e. organic solvents, heavy metals and DDT, their ability to cause cell detachment of cultured mouse neuroblastoma cells was investigated. A TD25 value was obtained by graphic estimation of the concentration needed to cause 25% of the total cell number to detach. These TD25 values were compared with LD50 values obtained from the literature and a correlation was found.

Mutagenesis by chemical agents in V79 chinese hamster cells: a review and analysis of the literature. A report of the Gene-Tox Program

The report reviews and evaluates the current literature (about 125 primary publications) on chemically induced specific locus mutations in the V79 Chinese hamster lung cell line. The V79 cell is convenient to use for mutagenesis studies since it has a rapid growth rate, high plating efficiency, and a stable karyotype. Mutation can be easily measured at either the hypoxanthine-guanine phosphoribosyl transferase or the Na+/K+ ATPase locus, both of which have been well characterized. Other less-studied markers are also described. We discuss the protocols for quantitative mutation studies including measurements of cytotoxicity, mutant expression times, mutant selection agents, cell densities during selection, and the stability and verification of mutant phenotypes. Mutations in the V79 cells by chemicals that require activation can be tested after their metabolism by cell homogenates or by intact cells, and the results with each type of activation are compared. For purposes of analysis, we classified a compound as mutagenic if it induced a mutation frequency that is at least 3 times higher than the spontaneous mutant frequency reported for that specific experiment. By this criterion two-thirds of the chemicals analyzed were mutagenic--; 11% with and 55% without metabolic activation. Of the 191 chemicals examined; 119 were polycyclic aromatic hydrocarbons; 25 were nitro or nitroso compounds, 9 were alkyl halides; 7 were purine or pyrimidine derivatives and the remaining 31 were from other chemical classes. We also defined mutagenic potency as the concentration of a compound that increases the mutant frequency by 10 times the spontaneous frequency. Mutagenic potencies of the compounds examined varied over a range of 5 X 10(6). We have also found large interlaboratory variations in the mutagenic potencies. Such variation in potency could be reduced by normalizing the results to a standard mutagen such as N-methyl-N'-nitro-N-nitrosoguanidine. The role of the V79 assay in mutagenicity and carcinogenicity testing is discussed and recommendations are suggested for future investigation.

Bronchogenic carcinoma and postoperative empyema: is survival really enhanced?

From 1959 to 1974, 542 patients underwent curative resection for bronchogenic carcinoma. Postoperative empyema occurred in 17 of these patients. The overall 5-year survival of these 17 patients was only 18%, compared with 27% in the 525 patients without empyema. We were unable to demonstrate by our study or by a review of the literature that postoperative empyema favorably influences survival in patients who have had pulmonary resection for bronchogenic carcinoma.

Prenatal diagnosis of neural tube defects: predictive value of AF-AFP in a low-risk population

Amniotic fluid alpha-fetoprotein (AF-AFP) determinations were performed on 1,215 women who were at low risk for fetal neural tube defects and who were undergoing mid-trimester amniocentesis for cytogenetic indications, primarily age-related aneuploidy. Maternal sera obtained before amniocentesis and amniotic fluids were assayed in duplicate for alpha-fetoprotein by radioimmunoassay. Of the 1,215 low-risk women, eight (0.7%) had significant elevations of AF-AFP (greater than or equal to +5 SD). In none of the cases was the elevation associated with a fetal neural tube defect. Two cases with elevated AF-AFP were associated with chromosome aberrations; one with impending fetal demise; one with fetal blood contamination; and one case was due to a laboratory error. In one case, no source for the elevated AFP was found, and a normal infant was delivered at term. In the final two cases, the cause of the elevated AF-AFP was a fetal abdominal wall defect (one gastroschisis and one omphalocele). The predictive value of an elevated AFP varies with the population screened, and is reduced by routine ultrasonography before amniocentesis, which at least identifies anencephaly. In a low-risk population, an elevated AF-AFP is most often not associated with a fetal neural tube defect. Because of the low predictive value and the nonspecificity of AF-AFP, genetic counselors should reconsider the recommendation of routine AF-AFP in low-risk maternal populations.

Treatment of caustic injuries of the esophagus: a ten year experience

The methods of managing 32 patients sustaining caustic injuries to the esophagus are assessed. Treatment of these patients must be individualized according to the type of caustic ingested, the degree of burn and other clinical signs. While an aggressive approach is favored for second and third-degree burns in the form of early esophago-gastrectomy with subsequent colon interposition, operation is not necessary. In all patients, particularly those with first-degree burns. The use of antibiotics is recommended as soon as the diagnosis of esophageal injury is established. The efficacy of steroids in preventing stricture formation, especially with third-degree burns, is questioned.

Degradative behavior of a new bronchodilator, carbuterol, in aqueous solution

The degradation kinetics of carbuterol in aqueous solution were investigated at 85 degrees and constant ionic strength over the pH 0.25--13.3 range under anaerobic conditions. The results demonstrated a complex kinetic pattern involving specific acid and specific base catalyses at the pH extremes. Degradation resulted primarily from intramolecular catalysis and indicated that both the protonated and unprotonated phenolic groups participated in the reaction. High-pressure liquid chromatography was used to isolate carbuterol and its degradation product. Mass spectrometric examination showed that the degradation product was a cyclized derivative formed by intramolecular attack of the phenoxy group on the ureido carbonyl with ammonia expulsion. The apparent activation energy for carbuterol at pH 4.0 and 10.0 was 22.3 and 11.7 kcal/mole, respectively. The agreement between the calculated theoretical pH--rate profile and the experimental points supports the hypothesis presented concerning the reactions involved in carbuterol degradation.

Cell surface antigens containing beta2-microglobulin as the common subunit

beta2-Microglobulin, which was first discovered in various biological fluids, has been shown to be the common subunit of the human HLA-A,B,C antigens. In the mouse beta2-microglobulin is associated with H-2K, D and L antigens and with TL and Qa-2 antigens, beta2-microglobulin and the heavy HLA antigen chains are similar in structure to the immunoglobulins and it is suggested that the two types of molecules have had an interrelated evolution. Data are also presented which suggest that the structural similarity between transplantation antigens and immunoglobulins may be paralleled by a functional similarity as well.

Nitroglycerin infusion during infrarenal aortic cross-clamping in dogs: an experimental study

The effects of an intravenous infusion of nitroglycerin on cardiac index and peripheral vascular resistance during infrarenal aortic cross-clamping were determined in normal animals and in animals subjected to low cardiac output state. Both groups of untreated animals demonstrated progressive fall in cardiac index with a rise in total peripheral resistance during infrarenal aortic cross-clamping. The infusion of nitroglycerin during the period of aortic cross-clamping prevented the increase in total peripheral resistance and therefore prevented the progressive fall in cardiac index that occurred in untreated animals. In the animals with depressed myocardial function, the infusion of nitroglycerin produced a 44% increase in cardiac index during aortic cross-clamping. The results of this study showed that the infusion of nitroglycerin during abdominal aortic cross-clamping can prevent adverse cardiovascular sequelae from occurring and should be used in patients undergoing abdominal aortic resection, especially those with impairment of left ventricular function.

The effect of glucagon in animals on chronic propranolol therapy

Eleven adult mongrel dogs were divided into two groups. Group 1 animals served as controls and Group 2 received propranolol (6 mg/kg/day) orally in divided doses for 15 to 21 days. Prior to cardiopulmonary bypass, cardiac output, first derivative of left ventricular pressure (dp/dt), peak systolic pressure, heart rate, and central venous pressure were recorded. The animals were then placed on cardiopulmonary bypass and subjected to 30 minutes of global ischemia at the myocardial temperature of 32 degrees C. Following cessation of cardiopulmonary bypass the baseline studies were repeated. In Group 2 animals following the repeat studies, glucagon was administered at a rate of 0.13 microgram/kg/min. The cardiac index and dp/dt were decreased by 43.3% (p less than 0.001) and 40.5% (p less than 0.001) in comparison to Group 1 animals. In Group 2 dogs, after bypass and glucagon infusion, cardiac index increased by 38% (p less than 0.02), dp/dt rose by 78% (p less than 0.05), and peak systolic pressure increased by 24.8% (p less than 0.05). These studies show the benefit of glucagon in the treatment of low cardiac output in the presence of beta-adrenergic blockade.

"What's wrong with my baby?"

The birth of a child with any developmental disability is an occasion of marked trauma to parents. Early, honest and frank counseling is imperative, and the family physician can play a unique role in this counseling process. When the physician is not knowledgeable in a paretcular case, he or she should seek expert help and fully utilize available community services.

Hematin treatment of acute porphyria. Early remission of an almost fatal relapse

Intravenous infusions of hematin in a young woman with acute porphyria in profound relapse was followed within 48 hours by remission of symptoms and rapid recovery. From a state of severe central and peripheral nervous-system involvement, the patient recovered so completely that she was able to leave the hospital in less than a month, with only a residual weakness of her arms. Serial studies of serum and urinary levles of porphyrin precursors and serum level of hematin provided highly important information about the effect of hematin on acute porphyria.

Response of mice to repeated photoperiod shifts: susceptibility to stress and barbiturates

Three inbred strains of mice selected for their spontaneous aggressive behavior and differential susceptibility to stress were exposed to a controlled environment where on an average of once every 4 days for 76 days and subsequently on an average of once every 2 days for an additional 55 days a 12L:12D photoperiod was reversed by 180 degrees. This procedure did not affect the growth of the mice and appeared to reduce fighting. However, plasma corticosterone concentrations in all three strains of mice were high, and their response to a 24-hr cold stress was no longer evident. The most pronounced effect of the altered photoperiod was on the barbiturate-induced sleeping time which showed a 40% reduction in all strains in spite of differential suceptibility to the drug among strains. It is concluded that repeated random phase shifting by varying the photoperiod is a stressful experience to which animals do not adapt and that the ability to respond to an additional stimulus or drugs may be greatly altered.

Automated Simultaneous Determination of p-Aminohippurate and Creatinine in Plasma or Urine

Methods have been developed for using the Beckman "Discrete Sample Analyzer" (DSA-560), for automated simultaneous determinations of p-aminohippurate (PAH) and creatinine in the same 50- or 10-µl samples of plasma or urine, respectively, at the rate of 80 samples per hour. In determinations of PAH, a single reagent, p-dimethylaminocinnamaldehyde in 0.1 mol/liter HCl, was added to a protein-free filtrate from plasma or urine. The intensity of the color, measured at 550 nm, obeyed Beer’s law for PAH concentrations from 0.005 to 5.0 g/liter. Data obtained for the same plasma and urine samples by the manual method, were, in general, within ±5% of the results obtained by the automated method. Creatinine was simultaneously determined by adapting the method of Taussky to the DSA-560 instrument; the intensity of the color, measured at 510 nm, obeyed Beer's law for creatinine concentrations ranging from 0.005 to 5.0 g/liter. Data obtained for the same plasma and urine samples by the manual method, were, in general, within ± 5% of the results obtained by the automated method.

Intrarenal conversion of angiotensin I to angiotensin II in the dog

Effects of close intra-arterial injections of angiotensins I and II on changes in renal blood flow and renal vascular resistance were studied in dogs anesthetized with pentobarbital sodium. In the first series of experiments, angiotensin I (0.375 µg) or angiotensin II (0.13 µg) decreased renal blood flow and pressures in a small renal cortical vein and the renal vein. Although renal vascular resistance was markedly increased by angiotensins I or II, these increases did not appear to involve renal venous segments. Responses to angiotensin I occurred when the injected agonist was not allowed to reach the systemic circulation, and were virtually abolished during infusion of SQ 20475, a synthetic pentapeptide (Pyr-Lys-Try-Ala-Pro) that inhibits enzymatic conversion of angiotensin I to angiotensin II. In the second series of experiments, renal vascular responses to intra-arterial injections of angiotensin I (0.375-3.75 µg) and angiotensin II (0.13-1.00 µg) were studied. Responses to angiotensin I, but not those to angiotensin II, were significantly attenuated by SQ 20475. The results suggest that similar renal vascular segments respond to angiotensins I and II. Responses to angiotensin I are probably due to its intrarenal conversion to angiotensin II. Such conversion appears to occur to the extent of about 4%.