Mutations in the right operator of bacteriophage lambda: evidence for operator-promoter interpenetration

A set of virulent mutants of bacteriophage lambda have been selected from λv2 v3. The sites of mutation form two microclusters, both close to v3. Some of the mutants, selected for their ability to grow on a λ-lysogen, can also grow on a λdv carrier strain. They are called “supervirulent” and a mutation conferring super-virulence is called vs. The sites of mutation to vs lie between the presumed promoter mutants (x3, x7) and x13, implying that the operator and promoter interpenetrate each other. The relative affinities of λ repressor for binding, in vitro, to λv⁺, λv3, λvs326, and λv3 vs327 DNA were 1, $\text{1}\text{4}$, $\text{1}\text{20}$, and $\text{1}\text{4000}$, respectively. We suggest that two separate mutations in the right operator are needed to confer virulence because promoter sites lie within the operator.     

Ovarian responses of seasonally anestrous ewes administered progesterone,PMS, HCG and(or) GnRH

One hundred and sixty ewes were assigned to sixteen groups in a 2 × 2 × 4 factoral design and were treated during the anestrous season. The main effects were progesterone pretreatment (non-implanted and implanted for 14 days), PMS pretreatment (no pretreatment and pretreatment with 500 IU at the time of progesterone implant removal) and treatments (none, GnRH in saline, GnRH in gelatin capsules and HCG). GnRH in saline (250 μg) and HCG (500 IU) were administered intramuscularly and GnRH in gelatin capsules (250 μg) was administered subcutaneously 24 hours after the time of progesterone implant removal.Ewes were classified into one of four progesterone response categories: cyclic, transient, prolonged and no response. An injection of GnRH in saline induced a prolonged progesterone response in only one ewe (13%) which was similar to the response in the untreated ewes (0%). More ewes administered GnRH in gelatin capsules (56%) and more ewes administered HCG (89%) had a prolonged progesterone response than GnRH (in saline) treated or untreated ewes. A higher percentage of ewes that were pretreated with PMS and treated with GnRH in saline (78%) had a prolonged progesterone response than ewes treated with either PMS (22%) alone or with GnRH (in saline; 13%) alone.     

Induction of male sex behavior in pony mares with testosterone propionate

Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrous mare. The testosterone propionate-treated mares mounted and bit estrous mares more frequently than the stallion but exhibited less sniffing, flehmen and vocalization behavior in the presence of an estrous mare than the stallion. Testosterone propionate-treated mares and the stallion mounted an estrous mare 23.3 +/- 9.7 seconds and 172.5 +/- 22.5 seconds, respectively, after being introduced into the pen. Mares in estrus were mounted by the testosterone propionate-treated mares and the stallion an average of 4.0 +/- 1.3 and 1.0 +/- 0 times, respectively, during a ten-minute test. None of the non-estrous mares was ever mounted by the testosterone propionate-treated mares. In summary, testosterone propionate induced male sex behavior in intact mares and the testosterone propionate-treated mares effectively detected estrous mares.     

Steady state kinetic mechanism of the Escherichia coli coenzyme A transferase.

Developing chloroplasts isolated from greening cotyledons and isolated etioplasts were capable of synthesizing and accumulating Mg-protoporphyrin IX monoester and longer wavelength metalloporphyrins when incubated in the dark in the presence of protoporphyrin and cofactors. These results constituted the first unambiguous demonstration of the insertion of magnesium into exogenous protoporphyrin in a cell-free system from higher plants. The metalloporphyrin synthetic activity did not occur in the absence of the plastids or when the plastids were heated in a 100 °C water bath for 2 min. It is thus suggested that, in higher plants, the in vitro insertion of magnesium into protoporphyrin is an enzymatic reaction.     

Differentiation of chloroplast lamellae: Light harvesting efficiency and grana development

Incomplete development of chloroplast lamellae occurred when etiolated pea plants were greened under cycles of 2 min light, 118 min dark. Although the plastids had full photochemical activities, they were nearly agranal. They were also characterized by a high quantum requirement for whole chain electron transport in low light; this is thought to be the result of unequal light absorption by incompletely developed light-harvesting assemblies of photosystem I and II and a lack of regulation of excitation energy distribution between the two photosystems. Continuous illumination induced the final stages of membrane differentiation. These stages were primarily characterized by the appearance of grana stacking and an increase in photosynthetic unit size. A biphasic decrease in quantum requirement for whole chain electron transport correlated directly with the appearance of grana during the final steps of membrane assembly. Structural organization of the membrane may be related to the light-harvesting efficiency of the membrane.     

A role for sialic acid containing substrates in the exocytosis-like in vitro interaction between adrenal medullary plasma membranes and chromaffin granules

The “in vitro” interaction between bovine adrenal medullary plasma membranes and chromaffin granules has recently been proposed as a putative cell-free model for exocytosis because calcium ions specifically control the plasma membrane-induced release of 10^?7 and 10^?5 M. Addition of ruthenium red or pretreatment with neuraminidase gradually blocks this interaction indicating that sialic acid containing substrates may be of major importance. These observations and similar results obtained by other authors working on different systems suggest a role for sialic acid containing moieties in exocytosis.     

The primary structure of the human pancreatic secretory trypsin inhibitor: Amino acid sequence of the reduced S-aminoethylated protein

The amino acid sequence of human pancreatic secretory trypsin inhibitor [Pubols, M. H., Bartelt, D. C., and Greene, L. J. (1974) J. Biol. Chem., 249, 2235–2242] was determined by a combination of selective trypsin and chymotrypsin hydrolysis reactions on the S-2-aminoethylcysteinyl inhibitor and conventional methods (subtractive Edman degradation and exopeptidase hydrolysis) for sequence determination of small peptides. The peptides were ordered on the basis of the identification of the amino- and carboxyterminal residues of the products at each stage of the degradation procedure. The sequence determination was carried out on a mixture of chromatographic forms present in both tissue and pancreatic juice which are identical in amino acid composition, aminoterminal residues, molecular weight, and specific activity, but differ only in asparagine content and susceptibility to enzymatic hydrolysis. The amino acid sequence of the human inhibitor corresponding to chromatographic form A₃ has been shown to be NH₂

.     

The rise in chlorophyll a fluorescence yield and decay in delayed light emission in Tris-washed chloroplasts in the 6–100 μs time range after an excitation flash

Parallel measurements of the rise in chlorophyll a fluorescence yield and delayed light emission decay, after a 10 ns saturating excitation flash, have been made in tris(hydroxymethyl)aminomethane-washed chloroplasts. Various electron donor systems (Mn²⁺; ascorbate; reduced phenylenediamine and benzidine) were used in conjuction with different preillumination regimes to alter [P⁺-680], the oxidized form of the Photosystem II reaction center chlorophyll a. Conditions giving rise to high [P⁺-680] resulted in only a small rise in fluorescence yield, an inhibition of a 6 μs delayed light component, and an enhancement of a 60 μs component of delayed light emission. These results confirm the hypothesis that P⁺-680 acts as a quencher of fluorescence and that delayed light emission in the microsecond time range is due to the back reaction of P⁺-680 and Q^?. (Q is the first “stable” electron acceptor of Photosystem II.) Two preillumination flashes are required before the full effect of Tris washing is observed in the delayed light emission decay and fluorescence yield rise; this suggests that a capacity to hold two charges exists between the Tris block and P⁺-680. Tris washing has no direct effect on the movement of electrons from Z (the first electron donor to P⁺-680) to P⁺-680. Finally, Mn²⁺ donates electrons to P⁺-680 via Z.