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.     

Centrioles and Microtubules in <Emphasis Type="Italic">Chlorella</Emphasis>

IN keeping with its widespread use in biochemical studies, the ultrastructure of the unicellular green alga Chlorella has been investigated many times^1–3, yet at least two components—microtubules and centrioles—have escaped detection, doubtless because of the use of inadequate fixation techniques. We report here on the presence and behaviour of these subcellular components during the cell cycle in C. pyrenoidosa 211-8p grown autotrophically in cultures synchronized⁴ by alternating light (time 0–15 h) and dark (15–24 h) periods and sampled for examination by electron microscopy following fixation in phosphate-buffered 2.5% glutaraldehyde (pH 6.7, 25° C, 2 h) and post-fixation in 2% osmium tetroxide (pH 7, 0° C, 2 h).     

Initiation of Cellulose Biosynthesis

IN spite of much investigation the problem of the molecular mechanism of cellulose synthesis remains unsolved¹. Hexose phosphates², sugar nucleotides^3–6 and a glycolipid^7–9 have been suggested as the precursor of cellulose. Implicit in all these investigations is the supposition that a single substrate suffices for the synthesis. We describe here some preliminary observations which seem to throw new light on the possible mechanism.     

Biological Interactions and the Realized Niche of Euplotes vannus from the Salt Marsh Aufwuchs

SYNOPSIS. Euplotes vannus , a hypotrich ciliate. grows well over broad ranges of temperature and salinity. It requires higher densities of food (> 1 × 10⁴ cells/ml) for rapid reproduction than do the other herbivores, the foraminiferan Al-logromia laticollaris (> 1 × 10² cells/ml), and the nematode Chromadorina germanica (∼ 1 × 10³ cells/ml), to which it was compared. If food levels were initially very high (∼ 1 × 10⁸ cells/ml) the ciliates reproduced rapidly and consumed the algae faster than it could reproduce. Some balance between the algae and the ciliates was achieved at initial algal concentrations of ∼ 1 × 10⁵ cells/ml. In microcosm experiments at 25 C with equal numbers of C. germanica and A. laticollaris. E. vannus proved to be a very poor competitor; reaching only 20% of control levels when grow with C. germanica and only 13% when cultured with A. laticollaris . It was a better competitor in 2-species microcosms, at lower temperatures, and when its ratio to the other species was initially higher.
The experimental evidence suggests that E. vannus is best adapted to being a migrating initial colonizer of fresh algal blooms.