Heat labile opsonins to pneumococcus. I. Participation of complement.

Heat labile opsonins (HLO) in normal rat serum to both encapsulated and unencapsulated pneumococci (a) have the same heat lability as complement (C); (b) are active at 37 degrees C but not at 0 degrees C; (c) are inactivated proportionately to hemolytic C by the addition of immune aggregates to the serum; (d) are adsorbed from serum nonspecifically by bacteria at 37 degrees C but not at 0 degrees C; (e) are Ca(++)- and/or Mg(++)-dependent in their action; and (f) are inactivated by zymosan and a purified cobra venom factor, and in the case of encapsulated pneumococci, at least, by NH(4)OH. Like other opsonins, HLO to pneumococci act primarily on the bacteria rather than on the phagocytes. Their combined properties indicate that they involve multiple components of the hemolytic C system. Since HLO are immunologically polyspecific, they presumably play a broad protective role in the early (preantibody) phase of acute bacterial infections.

Studies on the effect of experimental nonketotic diabetes mellitus on antibacterial defense. I. Demonstration of a defect in phagocytosis.

Chronically diabetic nonketotic rats were shown to be more susceptible to experimental Type 25 pneumococcal pneumonia than nondiabetic rats. The cumulative mortality in the diabetic group was significantly higher at infecting doses of 10(3), 10(4), 10(5), and 10(6) organisms, and the LD(50) was less than one twentieth of that for the nondiabetic group. More than ten times as many viable pneumococci were found in the pneumonic lesions of the diabetic animals at 24 and 36 hr as were present in the lesions of the nondiabetic controls, and serial histologic studies revealed that phagocytosis was strikingly depressed in the alveolar exudates of the diabetic animals. The diabetic state was also found to cause a similar depression of in vivo phagocytosis in preformed peritoneal exudates. The results of in vitro experiments indicated that the principal defect in the diabetic animals resided in their serum rather than in their polymorphonuclear leukocytes. The depressive factor in the serum was identified as the abnormally high concentration of glucose. Since equivalent molar concentrations of unmetabolized sugars added to normal serum caused a similar depression of phagocytosis, it was tentatively concluded that the action of the glucose on the leukocytes was primarily osmotic. The sensitivity of the granulocytes to the glucose effect, however, depended upon the conditions of the phagocytic test. Only when the pneumococci were encapsulated and the leukocytes derived from inflammatory exudates were crowded together, as in vivo, was the depressive action of the glucose clearly demonstrable.

Heat labile opsonins to pneumococcus. II. Involvement of C3 and C5.

When encapsulated type 25 pneumococci (Pn25) were opsonized with normal guinea pig serum, they consumed much more C3 than other complement (C) components. Fixation of C3 to the organisms was demonstrated by radio-labeling techniques, and its capsular localization was established by the use of monospecific anti-C3 antibody. Treatment of the serum with an appropriate dose of a purified cobra venom factor (VF) destroyed C3 and all of the opsonic activity, without appreciably affecting the other C components. Addition of purified C3 completely restored the opsonic activity of the VF-treated serum, indicating a requirement for C3. Since purified C3 alone had no opsonic activity, it was concluded that the C3 molecules had to be cleaved (to C3b) to function as opsonins. Experiments with C5-deficient mice revealed that C5 also plays a definite, but quantitatively less impressive, role in antipneumococcal defense.

Studies on the pathogenesis of fever. XIX. Localization of pyrogen in granulocytes.

Only intact exudate granulocytes from rabbits generated large amounts of endogenous pyrogen when incubated in 0.15 M NaCl. No matter how whole-cell lysates or combinations of subcellular fractions were incubated, their yields of pyrogen never approached those of whole cells; at most, only minimal amounts of pyrogen were formed, once the integrity of the cells had been destroyed. Some pyrogen could be extracted from disrupted cells, but never more than a fraction (<25%) of that released from incubated whole cells. The yield could be slightly improved by lowering the pH (to 3.5) and by increasing the volume of extraction fluid. Virtually all of the preformed pyrogen that could be extracted from sucroselysed cells was found in their cytoplasmic fraction. Contrary to the results of Herion et al. (3), none could be detected in the granular (or lysosomal) fraction. Likewise, all efforts to recover pyrogen from the membrane-nuclear fraction were unsuccessful. In keeping with the finding that preformed pyrogen is contained in the cytoplasmic fraction were the observations that practically all of the aldolase, a cytoplasmic enzyme, and very little of the acid phosphatase, a granular enzyme, were lost from the cells during the release of pyrogen. Lysozyme, an enzyme stored in both the granules and the cytoplasm, was partially released from the cells under the same circumstances. Neither the release of pyrogen nor its slight intracellular buildup that precedes release (4) were affected by concentrations of puromycin that block protein synthesis in the cells and prevent their activation. Hence, it is concluded that the release process, which also involves the formation of active pyrogen (4), does not require protein synthesis, whereas activation of the cells, which may involve the synthesis of an inactive precursor (2), does.

Studies on the pathogenesis of fever. XV. The production of endogenous pyrogen by peritoneal macrophages.

Macrophages from oil-induced peritoneal exudates in rabbits produce endogenous pyrogen when first activated by incubation in 4 hr exudate fluid and then stimulated by incubation in potassium-free isotonic sodium chloride solution. The failure of earlier investigators to obtain pyrogen from macrophages is explained, and the relevance of macrophage pyrogen to fevers of agranulocytosis and other diseases, in which mononuclear rather than granulocytic exudates predominate, is discussed.

Studies on the pathogenesis of fever. XIV. Further observations on the chemistry of leukocytic pyrogen.

Leukocytic pyrogen previously reported to contain an essential protein moiety, appears to be a lipid-protein complex having a molecular weight in the range of 10,000 to 20,000. Evidence that it contains essential lipid includes its inactivation by Cu(++), its lability in alkaline solutions (pH 8.5 and above), and its loss of pyrogenicity when extracted with acid-isooctane. Its solubility in 66% methanol, and the enhancing action of ethanol in freeing it from sonicated cells, suggest the presence of exposed lipid groups at its surface. Once the complex is separated from other proteins, its biological activity is readily destroyed. Although the lipid component is presumed to contain unesterified fatty acid(s), its precise composition is unknown. The finding of lipid in the active complex is in keeping with the hypothesis that the pyrogen is derived from leukocytic membranes.

Studies on the pathogenesis of fever. XVI. Purification and further chemical characterization of granulocytic pyrogen.

Small quantities of highly purified granulocytic pyrogen have been separated from contaminating proteins by disc electrophoresis in polyacrylamide gel. The biologically active material thus isolated was shown to be electrophoretically homogeneous at pH 9 and pH 3.8. Earlier work on the chemical properties of the pyrogen molecule has been extended to include: (a) estimation of its molecular weight by gel filtration; (b) demonstration of free sulfhydryl groups essential for its biological activity; and (c) evidence that it is not inactivated by exhaustive extraction with ethanolether or n-heptane.

Studies on the pathogenesis of fever. 18. Activation of leukocytes for pyrogen production.

Blood leukocytes, in contrast to exudate leukocytes, release little or no pyrogen when incubated in 0.15 M NaCl unless previously activated by exposure to endotoxin or to a protein activator that is present in acute exudate fluid. The activation process, which also occurs during phagocytosis, involves the synthesis of cellular protein, presumably related to the pyrogen molecule. Evidence is presented that generation of pyrogen in sterile inflammatory lesions depends on both the activator and the anaerobic conditions in the exudate fluid.

Studies on the pathogenesis of fever. XVII. The cationic control of pyrogen release from exudate granulocytes in vitro.

Evidence has been presented that the release of active endogenous pyrogen from rabbit exudate granulocytes incubated in isotonic NaCl is a relatively prompt energy-dependent process that is preceded by a rise in intracellular pyrogen, and involves a rise in total intracellular cations and an increased permeability of the cell membranes, but does not require the synthesis of new proteins.

Synthesis of endogenous pyrogen by rabbit leukocytes.

Rabbit ieukocytes from peritoneal exudates and from blood were stimulated to form leukocyte pyrogen in the presence of radiolabeled amino acids. The stimuli used were endotoxin, phagocytosis, and tuberculin. The crude leukocyte pyrogen samples were purified; pyrogen from exudate cells was rendered homogeneous; pyrogen from blood cells was still contaminated with other proteins. All the purified pyrogens were radioactive; and for all it was shown that radioactivity and pyrogenic activity coincided on electrophoresis at pH 3.5 and pH 9 in acrylamide and on isoelectric focusing in acrylamide. Furthermore, pyrogens obtained from exudate cells stimulated in different ways, or from blood cells and exudate cells stimulated with endotoxin, appeared to be identical. These results suggest that leukocyte pyrogen was synthesized de novo from amino acid precursors and that leukocytes made the same pyrogen whatever the stimulus used to activate them.

Studies on the pathogenesis of fever. XX. Suppression and regeneration of pyrogen-producing capacity of exudate granulocytes.

Suppression of the pyrogen-producing capacity of exudate granulocytes results from incubation of the cells in plasma, serum, or Ringer's solution. When transferred in this state and incubated in isotonic NaCl, the cells release much less pyrogen than untreated exudate cells. The suppressive effect is reversible and appears to involve the cellular uptake of calcium ions. In contrast, regeneration of pyrogen-producing capacity in depleted exudate cells occurs only when the cells are incubated in serum. The process resembles activation and requires the cellular synthesis of protein.

Dosage compensation: X-repress yourself.

Dosage compensation in Caenorhabditis elegans involves the sex-specific recruitment to the X chromosome of a protein complex, the nature of which suggests that there are mechanistic links between chromosome segregation and global transcriptional regulation.

Aging. Stopping the clock.

Two genes that control dauer formation in the soil nematode Caenorhabditis elegans have direct effects on senescence.

Patterning in the C. elegans embryo.

Recent studies reveal preliminary insights into the mechanisms of embryonic patterning in Caenorhabditis elegans. It appears that both embryonic axes and early blastomere fates are determined by a combination of segregating determinants and cell interactions, under the control of maternally expressed genes. Later in embryogenesis, some regional identities are specified by a group of homeotic selector genes homologous to the HOM-C clusters in other animals. Intervening stages of specification, which could link these two classes of genes in a regulatory hierarchy, are beginning to be investigated.

Attachment of tail fibers in bacteriophage T4 assembly. Identification of the baseplate protein to which tail fibers attach.

A phage-neutralizing rabbit antiserum collected after immunization with tail-fiberless bacteriophage T4 particles was adsorbed with complete T4 phage. The resulting adsorbed serum inhibited tail fiber attachment in vitro. To identify the antigens against which this inhibitory activity was directed, blocking experiments were carried out with the adsorbed serum. Isolated complete baseplates and mutant-infected-cell extracts lacking known baseplate gene products but containing gene 9 product showed similar high levels of blocking activity. By contrast, both tail-fiberless particles lacking gene 9 product and infected-cell extracts made with gene 9 mutants showed 30-fold to 100-fold lower blocking activity. These results strongly support the conclusion that gene 9 product is the baseplate protein to which tail fibers attach.

Genetic analysis of X-chromosome dosage compensation in Caenorhabditis elegans.

We have shown that the phenotypes resulting from hypomorphic mutations (causing reduction but not complete loss of function) in two X-linked genes can be used as a genetic assay for X-chromosome dosage compensation in Caenorhabditis elegans between males (XO) and hermaphrodites (XX). In addition we show that recessive mutations in two autosomal genes, dpy-21 V and dpy-26 IV, suppress the phenotypes resulting from the X-linked hypomorphic mutations, but not the phenotypes resulting from comparable autosomal hypomorphic mutations. This result strongly suggests that the dpy-21 and dpy-26 mutations cause increased X expression, implying that the normal function of these genes may be to lower the expression of X-linked genes. Recessive mutations in two other dpy genes, dpy-22 X and dpy-23 X, increase the severity of phenotypes resulting from some X-linked hypomorphic mutations, although dpy-23 may affect the phenotypes resulting from the autosomal hypomorphs as well. The mutations in all four of the dpy genes show their effects in both XO and XX animals, although to different degrees. Mutations in 18 other dpy genes do not show these effects.

An autosomal gene that affects X chromosome expression and sex determination in Caenorhabditis elegans.

Recessive mutant alleles at the autosomal dpy-21 locus of C. elegans cause a dumpy phenotype in XX animals but not in XO animals. This dumpy phenotype is characteristic of X chromosome aneuploids with higher than normal X to autosome ratios and is proposed to result from overexpression of X-linked genes. We have isolated a new dpy-21 allele that also causes partial hermaphroditization of XO males, without causing the dumpy phenotype. All dpy-21 alleles show hermaphroditization effects in XO males that carry a duplication of part of the X chromosome and also partially suppress a transformer (tra-1) mutation that converts XX animals into males. Experiments with a set of X chromosome duplications show that the defects of dpy-21 mutants can result from interaction with several different regions of the X chromosome. We propose that dpy-21 regulates X chromosome expression and may be involved in interpreting X chromosome dose for the developmental decisions of both sex determination and dosage compensation.

Genetic definition of two functional elements in a bacteriophage T4 host-range "cassette".

Gene 37 of T4 encodes the major subunit of the distal half of the tail fiber. The distal tip of the fiber, comprised of the carboxy-terminal ends of two molecules of gene 37 product (gp37), carries the principal determinant of the phage host range. The gp37 carboxyl termini recognize the bacterial surface during infection, and, in addition, include a site required for interaction with the product of gp38 during distal half-fiber assembly. In the absence of interaction with gp38, gp37 polypeptides do not dimerize. Eleven temperature-sensitive mutants with defects located near the promoter-distal end of gene 37 were tested at nonpermissive temperatures for production of an antigen that is diagnostic of distal half-fiber assembly. Six of the mutations prevent distal half-fiber assembly. The other five allow assembly of distal half fibers, which combine with proximal half fibers and attach to phage particles, but the resulting phage do not adsorb to bacteria. These two classes of mutations define two adjacent but separate genetic regions, corresponding to two different functional domains in gp37. These two regions and the neighboring gene 38 comprise a functional unit that can be considered as a host-range "cassette," with features that are strikingly similar to corresponding functional units in other unrelated as well as related phages.

Effects of chromosomal deficiencies on early cleavage patterning and terminal phenotype in Caenorhabditis elegans embryos.

We have analyzed pregastrulation cleavage patterns in Caenorhabditis elegans embryos homozygous for various chromosomal deficiencies. By two different estimates these deficiencies represent between 37 and 49% of the genome, including the entire X chromosome and substantial portions of each of the five autosomes. Among these genomic regions, we find none whose absence causes defects in pregastrulation cleavage patterns. We can conclude that there are at most very few genes whose transcription after fertilization is required for normal early patterning of cell divisions. We also scored terminal phenotypes of the homozygous deficiency embryos for stage of arrest and for expression of three tissue-specific differentiation markers. Based on these phenotypes, we have identified regions of the genome that are required for completion of cell proliferation, expression of gut differentiation and entry into morphogenesis. Somewhat surprisingly, embryos in which cell proliferation is arrested at less than 20% of the normal cell number can nevertheless initiate morphogenesis and undergo elongation to the twofold stage. Our results are consistent with the view that many early events in C. elegans embryogenesis are controlled exclusively by maternally produced gene products. However, they are also consistent with the likely possibility that, at least in some deficiency embryos, although cleavage patterns may be normal, blastomere identities are not. In this respect the early cleavages may differ from later lineages, in which cell division patterns appear to be characteristic of cell identity.

A novel dominant transformer allele of the sex-determining gene her-1 of Caenorhabditis elegans.

We have characterized a novel dominant allele of the sex-determining gene her-1 of Caenorhabditis elegans. This allele, called n695, results in the incomplete transformation of XX animals into phenotypic males. Previously characterized recessive her-1 alleles transform XO animals into phenotypic hermaphrodites. We have identified five new recessive her-1 mutations as intragenic suppressors of n695. Three of these suppressors are weak, temperature-sensitive alleles. We show that the recessive her-1 mutations are loss-of-function alleles, and that the her-1(n695) mutation results in a gain-of-function at the her-1 locus. The existence of dominant and recessive alleles that cause opposite phenotypic transformations demonstrates that the her-1 gene acts to control sexual identity in C. elegans.