Effects of weaning age on mortality of colony-born Macaca nemestrina

In an effort to determine empirically the proper age for separation of pigtailed macaque (Macaca nemestrina ) infants from their dams in a large domestic breeding colony, we conducted a retrospective survey of 1,592 infants. Survivorship was highest for infants not separated from their dams at all and for those separated within the first four months of life. Survivorship was poor for animals separated during or after the fifth month. Thus, not weaning or weaning early are the most acceptable management strategies in terms of mortality risk. This result is paradoxical with regard to nutritional considerations, but appears to be related to a sensitive period in social development. The relative advantages and disadvantages of various weaning ages are discussed.     

Stimulation by calmodulin of Ca2+ uptake and (Ca2+-Mg2+) ATPase activity in membrane fractions from ox neurohypophyses

Calmodulin stimulated ⁴⁵Ca²⁺ uptake into a plasma membrane enriched fraction from ox neurohypophysial nerve endings and into a microsome fraction. The ⁴⁵Ca²⁺ uptake and the (Ca²⁺-Mg²⁺) ATPase activity in the plasma membrane fraction exhibited similar pCa and calmodulin sensitivities, suggesting that the enzyme activity is the biochemical expression of a high affinity Ca²⁺ pump. Calmodulin thus seems to play a role in regulation of the intracellular free Ca²⁺ concentration in the neurohypophysis.     

Central cardiovascular and thermal effects of prostacyclin in rats

Prostacyclin (PGI₂) induced a dose-dependent decrease in blood pressure with slight increases in heart rate and body temperature, when administered at the doses of 0.1–100 μg into the lateral cerebral ventricle (i.c.v.) of the urethane-anaesthetised rat. When the same doses were administered intravenously, both the blood pressure and heart rate decreased. Central pretreatment with sodium meclofenamate (1 mg/rat i.c.v.) antagonised the central hypotensive effect of PGI₂ but i.c.v. pretreatment of the rats with indomethacin (1 mg/rat) failed to affect the PGO₂-induced hypotension. Central pretreatment with two histamine H₂-receptor antagonists, cimetidine (500 μg/rat i.c.v.) or metiamide (488 μg/rat i.c.v.), antagonised the blood pressure lowering effect of 0.1 μg dose of PGI₂ but failed to affect the hypotension induced by higher PGI₂ doses. Therefore the main central hypotensive effect of PGI₂ seems not to be associated with the stimulation of histamine H₂ -receptors in the brain.The hypotensive effect of i.c.v. administered PGI₂ appears to be due to an action upon the central nervous system rather than to a leakage into the peripheral circulation. This assumption is supported by the fact that sodium meclofenamate i.c.v. antagonished the effect of PGI₂. In addition, the chronotropic response to i.c.v. PGI₂ was opposite to that induced by intravenous administration. The results also suggest that there may be differences in the mode of action between sodium meclofenamate and indomethacin.     

Preparation of radioactive iodinated cholylhistamine for use in the radioimmunoassay of cholic acid

A major handicap in the development of simple and accurate radioimmunoassay procedures for bile acids has been the lack of a radioactive standard of high specific activity. To provide such a compound, we first synthesized cholylhistamine using the carbodiimide reaction. The hypothesized structure was confirmed by elemental analysis, thin-layer chromatography, infrared and mass spectral analysis. The cholylhistamine was then iodinated with 125I, using the choloramine-T method. The 125I-cholylhistamine was bound by antisera raised against a cholic acid-bovine serum albumin conjugate. This procedure should prove useful in preparing radioactive conjugates for all of the bile acids.     

Computer simulation of engulfment and other movements of embryonic tissues

Using a model proposed earlier by Goel et al. and a set of plausible motility rules, a computer simulation of engulfment of two or more intact embryonic tissues is successfully carried out. The same motility rules are used to simulate the rounding up of a tissue, centralization of one tissue within another tissue (a phenomenon not yet observed), and phase inversion, a process which may have relevance to differentiation. The finnal structures bear a good resemblance to those observed experimentally. The software, in conjunction with an appropriate hardware configuration, allows a visual display of the dynamics of cellular movement. These simulations indicate that the range of inter-cellular interactions controlling these tissue rearrangements extends only one or two cell diameters.     

Primary in vitro antibody response of rabbit lymphoid cells and T-B cell collaboration in the absence of detectable mitogens

To investigate whether the antibody response and T-B-cell collaboration in vitro can be obtained in the absence of mitogens, a method of obtaining an in vitro primary anti-sheep red blood cell antibody response by rabbit spleen and lymph node cells was developed. We used Marbrook culture vessels and a specially prepared medium containing 10% autologous serum and maintained at pH 7.4–7.6. The system was shown to be devoid of any polyclonal mitogens as assessed by [³H]thymidine incorporation and by direct examination for blast cells in stained smears. The primary response increased continuously over the 5-day cultivation period and only IgM but not IgG plaque-forming cells (PFC) were detected. In over 20 experiments, the response ranged from 357 ± 17 to 4425 ± 110 PFC/10⁷ cultured cells with a median stimulation index of 52. The spleen cells required less antigen than the lymph node cells and 2-mercaptoethanol inhibited the response of the spleen cells but not that of the lymph node cells. Lymphocytes were separated into highly pure T- and B-cell populations by negative selection using antibody-coated human erythrocytes to rosette either T or B cells and Ficoll-Hypaque centrifugation to remove rosetted cells. Upon cultivation, B cells alone gave a low IgM response, whereas B cells reconstituted with T cells gave a response similar to that obtained with unseparated lymphoid cells. We concluded that: (a) optimal conditions for obtaining primary in vitro antibody responses using rabbit spleen and lymph node cells were established, (b) T-B-cell collaboration was demonstrated in the rabbit primary antibody response to sheep erythrocytes, and (c) the primary antibody response in vitro and T-B-cell collaboration may occur in the absence of detectable polyclonal mitogens.     

N-acetyl conjugates of basic amino acids newly identified in rat urine

Ninhydrin-negative conjugates of basic amino acids were isolated from rat urine and were characterized. The following conjugates of basic amino acids are the compounds newly identified in animal urine specimens, N^α-acetyl-N^π-methylhistidine, N^α-(N-acetyl-β-alanyl)histidine (N-acetylcarnosine), N^α-acetyl-N^G,N^′G-dimethylarginine, N^α-acetyl-N^G,N^G-dimethylarginine, and N^α-acetyl-N^?,N^?,N^?-trimethyllysine.     

Defect in 3'-phosphoadenosine 5'-phosphosulfate synthesis in brachymorphic mice. II. Tissue distribution of the defect

The tissue distribution of the defective PAPS synthetic pathway in homozygous brachymorphic mice ($\text{bm}\text{bm}$) has been investigated using four different criteria: (i) incorporation of ³⁵SO₄^2? into adenosine 5′-phosphosulfate (APS), 3′-phosphoadenosine 5′-phosphosulfate (PAPS), and endogenous macromolecular acceptors, (ii) APS kinase (adenylylsulfate kinase; ATP:adenylylsulfate 3′-phosphotransferase, EC 2.7.1.25) activity, (iii) ATP sulfurylase (sulfate adenylyltransferase; ATP:sulfate adenylyltransferase, EC 2.7.7.4) activity, (iv) thermostability of ATP sulfurylase. With respect to the first three criteria, the results indicate that liver is affected as profoundly as cartilage (K. Sugahara and N. B. Schwartz, Arch. Biochem. Biophys. (1982) 214, 589–601). In contrast, skin and brain show no differences between normal and mutant. Kidney is significantly, but only moderately, affected. The results from thermostability studies demonstrate that ATP sulfurylase activity is more labile in $\text{bm}\text{bm}$ cartilage, liver, and kidney, but not in skin or brain, supporting the above-observed distribution of the defect. Therefore, the present results indicate a multiple, but not universal, tissue distribution of the defective PAPS synthetic pathway in $\text{bm}\text{bm}$ mice. Furthermore, these findings support the suggestion that ATP sulfurylase as well as APS kinase is defective in brachymorphic mice.     

Adrenocortical cyclic GMP-dependent protein kinase: purification, characterization, and modification of its activity by calmodulin, and its relationship with steroidogenesis

Cyclic GMP-dependent protein kinase has been purified to apparent homogeneity from bovine adrenal cortex and its presence in the rat adrenal cortex has been demonstrated. Sucrose density sedimentation studies indicated that the M_r of the enzyme was 145,000. This protein was composed to two identical subunits each with M_r of 75,000. The enzyme molecule was asymmetric with a frictional coefficient of 1.54, Stokes radius of 53.5 Å and a sedimentation coefficient of 6.5. The enzyme self-phosphorylated and the stoichiometry of cyclic GMP binding was two molecules per holoenzyme. Calmodulin or troponin C markedly stimulated the apparent maximal velocity of cyclic GMP-dependent protein kinase without affecting its basal activity. This effect of protein modulators was independent of calcium. Sucrose density gradient studies indicated that the stimulatory effect of calmodulin was due to its interaction with histones. An interaction of calmodulin with the enzyme was not observed. The steroidogenic potential of cyclic GMP and its analogs correlated closely with their ability to stimulate cyclic GMP-dependent protein kinase; the order of potency for both activities was 8-bromocylic GMP > cyclic GMP > N²-monobutyryl cyclic GMP > N², O²-dibutyryl cyclic GMP. In each case, calmodulin enhanced the cyclic GMP-dependent protein kinase activity for histone phosphorylation. These results indicate that although cyclic GMP is the primary regulator of cyclic GMP-dependent protein kinase, other modulator proteins such as calmodulin could act as additional regulators of the phosphorylation of substrate proteins. In addition, the demonstration of cyclic GMP-dependent protein kinase in rat adrenal glands, and the results with cyclic GMP and its analogs relating to their activation of protein kinase and steroidogenesis are consistant with the concept that cyclic GMP is one of the mediators of adrenal steroidogenesis.