Mutagenesis of the putative alpha-helical domain of the Vpr protein of human immunodeficiency virus type 1: effect on stability and virion incorporation.

vpr is one of the auxiliary genes of human immunodeficiency virus type 1 (HIV-1) and is conserved in the related HIV-2/simian immunodeficiency virus lentiviruses. The unique feature of Vpr is that it is the only nonstructural protein incorporated into the virus particle. Secondary structural analysis predicted an amphipathic alpha-helical domain in the amino terminus of Vpr (residues 17-34) which contains five acidic and four leucine residues. To evaluate the role of specific residues of the helical domain for virion incorporation, mutagenesis of this domain was carried out. Substitution of proline for any of the individual acidic residues (Asp-17 and Glu-21, -24, -25, and -29) eliminated the virion incorporation of Vpr and also altered the stability of Vpr in cells. Conservative replacement of glutamic residues of the helical domain with aspartic residues resulted in Vpr characteristic of wild type both in stability and virion incorporation, as did substitution of glutamine for the acidic residues. In contrast, replacement of leucine residues of the helical domain (residues 20, 22, 23, and 26) by alanine eliminated virion incorporation function of Vpr. These data indicate that acidic and hydrophobic residues and the helical structure in this region are critical for the stability of Vpr and its efficient incorporation into virus-like particles.

Decrements in auditory responses to a repeated conspecific song are long-lasting and require two periods of protein synthesis in the songbird forebrain.

Earlier work showed that playbacks of conspecific song induce expression of the immediate early gene ZENK in the caudo-medial neostriatum (NCM) of awake male zebra finches and that this response disappears with repeated presentations of the same stimulus. In the present study, we investigated whether repetitions of a song stimulus also elicited a decrement in the electrophysiological responses in the NCM neurons of these birds. Multiunit auditory responses in NCM were initially vigorous, but their amplitude decreased (habituated) rapidly to repeated stimulation, declining to about 40% of the initial response during the first 50 iterations. A similar time course of change was seen at the single unit level. This habituation occurred specifically for each song presented but did not occur when pure tones were used as a stimulus. Habituation to conspecific, but not heterospecific, song was retained for 20 h or longer. Injections of inhibitors of protein or RNA synthesis at the recording site did not affect the initial habituation to a novel stimulus, but these drugs blocked the long-term habituation when injected at 0.5-3 h and at 5.5-7 h after the first exposure to the stimulus. Thus, at least two waves of gene induction appear to be necessary for long-lasting habituation to a particular song.

Rapid endocytosis of a G protein-coupled receptor: substance P evoked internalization of its receptor in the rat striatum in vivo.

Studies on cultured cells have shown that agonists induce several types of G protein-coupled receptors to undergo internalization. We have investigated this phenomenon in rat striatum, using substance P (SP)-induced internalization of the SP receptor (SPR) as our model system. Within 1 min of a unilateral striatal injection of SP in the anesthetized rat, nearly 60% of the SPR-immunoreactive neurons within the injection zone display massive internalization of the SPR--i.e., 20-200 SPR+ endosomes per cell body. Within the dendrites the SPR undergoes a striking translocation from the plasma membrane to endosomes, and these dendrites also undergo a morphological reorganization, changing from a structure of rather uniform diameter to one characterized by large, swollen varicosities connected by thin fibers. In both cell bodies and dendrites the number of SPR+ endosomes returns to baseline within 60 min of SP injection. The number of neurons displaying substantial endosomal SPR internalization is dependent on the concentration of injected SP, and the SP-induced SPR internalization is inhibited by the nonpeptide neurokinin 1 receptor antagonist RP-67,580. These data demonstrate that in the central nervous system in vivo, SP induces a rapid and widespread SPR internalization in the cell bodies and dendrites and a structural reorganization of the dendrites. These results suggest that many of the observations that have been made on the internalization and recycling of G protein-coupled receptors in in vitro transfected cell systems are applicable to similar events that occur in the mammalian central nervous system in vivo.

Letter from William Croswell to Joseph and David A. Croswell, 1825 July 20

Draft of a letter concerning Continental bills in Croswell's care.

Letter from William Croswell to Dr. E. Porter, 1828 May 20

Draft of a letter regarding Croswell's claims for compensation from the Harvard Corporation.

Letter from William Croswell to Andrew Croswell, 1828 June 20

Draft of a letter to Croswell's nephew regarding the family's history.

Letter from William Croswell to Joseph May, 1828 August 20

Draft of a letter regarding Croswell's Mercator map.

Payment order for Nathanael Gardner on behalf of his son, 1735 October 20

Handwritten order to John Sale to pay scholarship funds to Nathanael Gardner on behalf of his son Nathaniel Gardner (Harvard AB 1739), signed by Thomas Foxcroft, Charles Chauncey, Samuel Marshall, Zechariah Thayer, and Thomas Waite.

Bond between John Leverett and Elisha Cooke to John White, Treasurer of Harvard College, 1716 November 20

Two folio-sized leaves containing a one-and-a-half page copy of the bond between John Leverett and Elisha Cooke to John White, Treasurer of Harvard, for £200. The bond was witnessed by William Austin and Mary Gilbert. An October 3, 1726 receipt of payment from Nathaniel Byfield on the bond, signed by Treasurer Edward Hutchinson, is located on the verso of the first leaf.

[Form of Admission of Francis Oliver (Harvard AB 1795)], 1791 August 19-20

Printed certificate of admission for undergraduate Francis J. Oliver certified by Steward Caleb Gannett on August 19, 1791 and signed by President Joseph Willard on August 20, 1791.

[Certificate of admission of Justin Winsor], 1849 July 20

Printed copy of an undated abstract of laws and regulations with the admittatur of undergraduate Justin Winsor signed by President Jared Sparks on July 20, 1849.

Copy of Brimmer's suspension, 1803 April 20

Handwritten copy on one leaf of a vote of the Faculty suspending George Watson Brimmer (Harvard AB 1803) for neglect of his studies.