Primary structure of myosin from the striated adductor muscle of the Atlantic scallop, Pecten maximus, and expression of the Regulatory Domain

We have determined the complete cDNA and deduced amino acid sequences of the heavy chain, regulatory light chain and essential light chain which constitute the molecular structure of myosin from the striated adductor muscle of the scallop, Pecten maximus. The deduced amino acid sequences of P. maximus regulatory light chain, essential light chain and heavy chain comprise 156, 156 and 1940 amino acids, respectively. These myosin peptide sequences, obtained from the most common of the eastern Atlantic scallops, are compared with those from three other molluscan myosins: the striated adductor muscles of Argopecten irradians and Placopecten magellanicus, and myosin from the siphon retractor muscle of the squid, Loligo pealei. The Pecten heavy chain sequence resembles those of the other two scallop sequences to a much greater extent as compared with the squid sequence, amino acid identities being 97.5% (A. irradians), 95.6% (P. magellanicus) and 73.6% (L. pealei), respectively. Myosin heavy chain residues that are known to be important for regulation are conserved in Pecten maximus. Using these Pecten sequences, we have overexpressed the regulatory light chain, and a combination of essential light chain and myosin heavy chain fragment, separately, in E. coli BL21 (DE3) prior to recombination, thereby producing Pecten regulatory domains without recourse to proteolytic digestion. The expressed regulatory domain was shown to undergo a calcium-dependent increase (7%) in intrinsic tryptophan fluorescence with a mid-point at a pCa of 6.6.     

Tacrolimus and mycophenolate mofetil after nonmyeloablative matched-sibling donor allogeneic stem-cell transplantations conditioned with fludarabine and low-dose total body irradiation.

We evaluated tacrolimus/mycophenolate mofetil (MMF) for graft-versus-host disease (GVHD) prophylaxis after a nonmyeloablative stem cell transplantation (NST) from a matched sibling donor (MSD). Thirty-two patients (median age, 57 years) with advanced hematologic malignancies, who were poor candidates for a conventional myeloablative transplantation, received fludarabine (30 mg/m(2), day -4 to day -2), total-body irradiation (TBI) (200 cGy, day 0), infusion of donor peripheral blood progenitor cells (day 0), oral tacrolimus 0.06 mg/kg twice daily (from day 3), and oral MMF at 15 mg/kg twice daily (days 0-+27). Tacrolimus was tapered from day +100 to day +180 in those patients with indolent malignancies (n = 25), and from day +35 to day +56 in those with aggressive tumors (n = 7). Regimen toxicities and myelosuppression were mild, allowing 75% of patients to have entirely outpatient transplantations. One patient (3%) experienced a nonfatal graft rejection. Rates of grades II-IV and III-IV acute GVHD were 15.6% and 3%, respectively. Acute GVHD was diagnosed at median day +78 (range, days +31-+84). Extensive chronic GVHD was observed in 10 of 24 evaluable patients (41.6%) at a median onset of day +198 (range, days +128-+277), either spontaneously (n = 5) or elicited after tumor progression (n = 5). Five patients experienced transplantation-related mortality (TRM) (15.6%) from either acute GVHD-related multiorgan failure (MOF) (n = 3) or infectious complications (n = 2). At median follow-up of 19 months (range, 2-41 months), the overall survival, progression-free survival, and disease-free survival rates are 62.5%, 50%, and 40%, respectively. In conclusion, the use of tacrolimus/MMF after MSD NST is associated with encouraging rates of GVHD control.     

Modulation of stretch-evoked reflexes in single motor units in human masseter muscle by experimental pain

The interaction between muscle pain and motor function of the jaw has been examined in recent years, but the nature of the modulation of the short-latency stretch reflex by pain is not fully understood. In this study, the reflex responses to stretch were measured in single low-threshold motor units that were kept discharging at a constant frequency, before, during and after the induction of experimental pain in one masseter muscle by controlled infusion of hypertonic saline. The probability of evoking a reflex response in individual motor units in the painful muscle at near-monosynaptic latency was reduced by a mean of about 20%. However, the overall reflex response in the surface electromyogram of both the ipsi- and contralateral masseter muscles was greater during pain. This was apparently a secondary response to the pain-induced increase in pre-stimulus activity in the motoneurone pools of both muscles, because increased motoneurone excitability may facilitate stretch reflexes. It is concluded that the most likely explanation for the reduced reflex response of low-threshold masseter motor units during experimental pain is a tonic reduction in the fusimotor drive to the masseter spindles.     

Variant Philadelphia chromosome translocations in two patients with chronic myelogenous leukemia

Two patients with chronic myelogenous leukemia and new variant Philadelphia chromosome translocations are reported. In one case, a 41-year-old male, a 10;22 translocation was found in all bone marrow cells examined. Furthermore, the Y chromosome was missing in 90% of the analyzed metaphase cells. In the second patient, a 22-year-old male, all the marrow cells contained a complex rearrangement involving chromosomes No. 2, 9, and 22.     

Antigen-independent acquisition of MHC class II molecules by human T lymphocytes

We report here that human T lymphocytes have the capacity of acquiring large amounts of MHC class II molecules from various types of antigen-presenting cells (APC) in an antigen-independent manner. The transfer of MHC class II molecules from APC to T cell required direct cell-to-cell contact and appeared to involve the interaction of numerous adhesion molecules between these cells. Depletion of cholesterol from the plasma membrane reduced the amount of MHC class II transferred onto the T cells. Most significantly, the newly acquired MHC class II molecules were capable of efficiently presenting antigen to T helper cells. These results suggest that T cells are able to interact with other T cells to regulate immune responses by presenting MHC peptide complexes that have been snatched away from nearby APC.     

Structure and function of natural-killer-cell receptors

The function of natural-killer (NK) cells is modulated by the balance between a number of activating and inhibitory receptors. Killer immunoglobulinlike receptors (KIRs) are mostly inhibitory receptors. They play a critical role in recognizing self-class-I major histocompatibility complex (MHC) molecules and thus protect healthy host cells from NK-targeted lysis. In contrast, both NKG2D and CD16 are activating NK receptors that trigger the NK-cell lysis of various tumor and virally infected cells through either direct ligand engagement or antibody-dependent cellular cytotoxicity (ADCC). Through structural studies of members of these distinct receptor families, in particular, the structure and recognition between KIR2DL2 and HLA-Cw3, that between NKG2D and ULBP3, and that between CD16 and IgG Fc, considerable understandings have been achieved about their function and their ligand recognition.