Changes in Urease Activity in Apple Trees as Related to Urea Applications

Changes in urease (E.C.3.5.1.5.) were followed during the growth of 1-year-old MM 106 and 9-year-old Golden Delicious apple trees (Malus pumila Rehd.). Urease was found in leaves, roots, and bark with actively growing tissues containing more activity than senescing tissues. The urease activity in the leaves declined steadily during leaf senescence but abscised leaves still contained about half of their initial urease activity. In the bark the urease activity changed only slightly. Urease activities in the leaves and bark of apple trees were always greater in those trees which had received an application of urea. In senescing apple leaves, urea induced a rapid increase in urease activity. The changes in total activity and specific activity of urease were parallel and suggests that urease was synthesized de novo. After urease activity reached a maximum, a rapid decline occurred. Urease was inhibited by low concentrations of ammonia and this decline may be due to product inhibition.     

Remarks on the Composition of the Large Ciliate Class Kinetofragmophora de Puytorac et al., 1974, and Recognition of Several New Taxa Therein,with Emphasis on the Primitive Order Primociliatida N. Ord.*

With the realization that new data (especially ultrastructural) and new ideas are making necessary a major revision of the scheme of classification of the Ciliophora, several groups of ciliatologists are preparing treatises on the subject. The present paper is concerned with the composition of the large new class of ciliates, Kinetofragmophora de Puytorac et al., 1974, established very recently by the French group. Several new taxa, at ordinal and subordinal levels, are proposed for inclusion in that class, with special emphasis on the new order to contain the most primitive of extant species. Actions taken here are incorporated in a major review and revisory work of the author which is being published elsewhere. The class Kinetofragmophora, by far the largest of the 3 classes now recognized as comprising the whole phylum Ciliophora, is itself considered to contain 4 sizeable subclasses and to embrace a total of 13 orders and 14 suborders. Two orders and 6 suborders are named and described here as new, enumerated and briefly identified as follows: Order Primociliatida n. ord., for the most “primitive” of gymnostomes, with three new suborders— Homokaryotina n. subord., for the homokaryotic genus Stephanopogon; Karyorelictina n. subord., for a number of mostly interstitial ciliates which, though heterokaryotic, possess nondividing, diploid macronuclei (e.g. Trachelocerca, Trachelonema, and Tracheloraphis); and Prorodontina n. subord., for a group of relatively specialized formerly “rhabdophorine” gymnostomes such as Coleps, Placus, and Prorodon and order Haptorida n. ord., for rapacious carnivorous forms, formerly lumped with the preceding groups as “rhabdophorines,” many with oral toxicysts and well developed thigmotactic ciliature (e.g. Actinobolina, Didinium, Dileptus, Enchelys, Spathidium, and Trachelius). All foregoing taxa are members of the 1st kinetofragmophoran subclass, the Gymnostomata. In the taxonomic conclusions drawn, new significance is placed on ultrastructural data, on macronuclear differences of evolutionary importance, and on habitat and behavior. A brief review of the literature on psammophilous ciliates is presented. In the subclass Vestibulifera is now located the order Entodiniomorphida Reichenow, a group formerly considered to be a spirotrich taxon. A suborder, Blepharocorythina n. subord., is proposed to contain the old “trichostome” family Blepharocorythidae, species commensalistic in horses and ruminants and now—with their syncilia, etc.—considered ancestral to the ophryoscolecids and relatives. In the subclass Hypostomata, order Nassulida, the suborder Paranassulina n. subord. is established to contain nassulids which appear more highly evolved than Nassula itself (e.g. Paranassula and Enneameron) in perioral ciliature, mode of stomatogenesis, etc. In the enigmatic and still vexatious order Rhynchodida, the suborder Aneistrocomina n. subord. is erected to embrace rhynchodid genera with an anteriorly located sucking tentacle (and other unique characteristics)—for example, Ancistrocoma, Crebricoma, Holocoma, and Sphenophrya. With the banishment of the bulk of the old “thigmotrichs” to the oligohymenophoran order Scuticociliatida, the ancistrocomines are left with the family Hypocomidae (and relatives) in the order Rhynchodida. It is not yet clear, however, how closely related the 2 suborders of rhynchodids should be considered. Special nomenclatural problems are also involved.     

Antigens and Antigenic Variability of the African Trypanosomes*†

SYNOPSIS. The recent literature on the physical, chemical and biological characterization of antigens from the African trypanosomes is reviewed. The antigens are divided into three major groups: a) variant-specific antigens, b) common antigens, and c) host-like antigens. The variant-specific antigen(s) are relatively small molecular weight proteins located on the surface of the trypanosome, and are involved in protection and agglutination. It is suggested that there is more than a single variant-specific antigen on the cell surface. In contrast, the common antigens are internal or somatic antigens which are believed to have structural or enzymatic functions but are not involved in either protection or agglutination. In addition, evidence is also presented which suggests that there are host-like antigens within the surface coat and/or membranes of the trypanosomes. The importance of these three groups of antigens, and the mechanis(s) of antigenic variation are discussed in relationship to the immune response of the host to the African trypanosomes. Several possible approaches for future investigations are described.     

Exploration and Social Play in Squirrel Monkeys (Saimiri)

Squirrel monkeys (Saimiri) have been studied in a variety oflaboratory and natural environments. The frequency and formof exploration and social play vary considerably among differentenvironments. For example, in some environments, young monkeyshave been observed to play for 3 hr per day; but in one naturalenvironment, not a single bout of social play was seen duringa 10-week intensive study. Numerous intermediate levels of playactivity have been observed. Whereas many theories of play make it appear that play is essentialfor the development of sexual behavior, integrated roles introop structure, control of aggressive responses, social cohesion,etc., the data on squirrel monkeys indicate that social organizationand many normal social behaviors can develop without socialplay. However, the opportunity to play socially provides learningexperiences that increase the variety of each animal's behavioralrepertoire and the subtly of social cues to which it can respond.An adaptive modicum of competence can appear without socialplay, but the opportunity to play socially develops the competenceof animals beyond that modicum.     

Immunoreactive Parathyroid Hormone in Circulation of Man

WE have reported that parathyroid hormone (PTH) is secreted from the parathyroid in vivo as a polypeptide of eighty-four amino-acids, identical to the hormone stored in the glands (molecular weight of 9,500), but that the hormonal polypeptide is cleaved after it enters the general circulation¹. A large hormonal fragment from this cleavage, with a molecular weight of approximately 7,500, has been identified in the circulation. The fragment differs immunologically from the hormone secreted and extracted from the glands¹. To analyse the biological significance of the metabolism of the hormone and the chemical nature and hormonal activity of the large circulating fragment, we have developed radioimmunoassays that specifically measure the amino-terminal (N-assay) and carboxyl-terminal (C-assay) regions of the hormonal molecule. We now report that much higher concentrations of immunoreactive hormone are found in the general circulation by the C-assay than by the N-assay. The studies with the N-assay indicate that the large fragment has lost a portion of the amino-terminal sequence required for biological activity⁹. Since the fragment is present in much higher concentration than native uncleaved hormone, we must conclude that much of the immunoreactive PTH detected in the circulation is biologically inactive.     

Direct Action of Insulin on Plasma Membrane ATPase Activity in Human Lymphocytes

LITTLE is known about the effects of insulin on lymphocytes. Helmreich and Eisen¹ concluded that it has insignificant effects, but others^2–5 have made a case for a role in inflammatory and immunological responses. We^6,7 have demonstrated that noradrenaline enhances the uptake of both glucose and potassium by lymphocytes, as does insulin in several tissues. We have associated this action of noradrenaline with a direct effect on membrane adenosine triphosphatase (ATPase) activity⁷. The observation⁸ that insulin bound to ‘Sepharose’ polymers enhances glucose transport while in contact only with the plasma membrane indicated that insulin might have a direct action similar to that of noradrenaline on membrane ATPase. The observations reported here show that insulin stimulates ATPase activity and glucose uptake in the lymphocyte and suggest a relationship between membrane ATPase activity and glucose transport.     

Attempt to Identify the Agent for Creutzfeldt-Jakob Disease by CF Antibody Relationship to Known Viruses

CREUTZFELDT-JAKOB disease (C-J disease), a subacute spongiform virus encephalopathy responsible for a fatal presenile dementia of man, has been experimentally transmitted to the chimpanzee and passed serially from chimpanzee to chimpanzee^1,2. The disease may be caused by the activation of a common virus which had remained latent after primary infection or by the development in vivo of a neurotropic variant of a common virus previously acquired. We have attempted to identify the agent of C-J disease by searching for serum antibodies to known viruses in thirteen patients and ten experimentally infected chimpanzees. Although we have failed to identify the causative agent, there is strong evidence against a serological relationship with any of the viruses tested.     

Antibody of Restricted Heterogeneity secreted by Spleen Fragments

SMALL fragments of lymphoid tissue in culture will incorporate radioactive amino-acids into secreted immunoglobulin. Electrophoresis followed by autoradiography has been used to indicate the degree of heterogeneity of the immunoglobulin^1–5. Fragments of lymph node from a rabbit immunized with low doses of Salmonella organisms^2–4 and of spleens from reconstituted irradiated mice immunized with sheep erythrocytes⁵ have been studied.     

Normal and Mutant Glycine Transfer RNAs

THE glycine-specific tRNAs of E. coli can be grouped into three subspecies which are separated by chromatography on benzoylated DEAE cellulose (BDC): tRNA^Gly₁ (GGG), tRNA^Gly₂ (GGA/G) and tRNA^Gly₃ (GGU/C)^1,2. The tRNA^Gly₁ and tRNA^Gly₂ are specified by the genes, glyU and glyT, respectively, which have been located at 55 and 77 minutes on the E. coli chromosome. Suppressors of tryptophan A gene (trpA) missense mutations and partial diploid strains have been used extensively to characterize the glycine tRNA structural genes (Table 1)^1–3. A common property of these suppressor mutations is that the altered tRNA^Gly is no longer aminoacylated at the normal rate by the glycyl tRNA synthetase (GRS). When ordinary loading conditions are used virtually none of the suppressor tRNA species are amino-acylated. These studies have shown that single gene copies are normally present at the glyT and glyU loci.