Hydrophilic peptides derived from the transframe region of Gag-Pol inhibit the HIV-1 protease

The HIV-1 transframe region (TFR) is between the structural and functional domains of the Gag-Pol polyprotein, flanked by the nucleocapsid and the protease domains at its N and C termini, respectively. Transframe octapeptide (TFP) Phe-Leu-Arg-Glu-Asp-Leu-Ala-Phe, the N terminus of TFR, and its analogues are competitive inhibitors of the action of the mature HIV-1 protease. The smallest, most potent analogues are tripeptides: Glu-Asp-Leu and Glu-Asp-Phe with Ki values of approximately 50 and approximately 20 microM, respectively. Substitution of the acidic amino acids in the TFP by neutral amino acids and d or retro-d configurations of Glu-Asp-Leu results in an >40-fold increase in Ki. Protease inhibition by Glu-Asp-Leu is dependent on a protonated form of a group with a pKa of 3.8; unlike other inhibitors of HIV-1 protease which are highly hydrophobic, Glu-Asp-Leu is extremely soluble in water, and its binding affinity decreases with increasing NaCl concentration. However, Glu-Asp-Leu is a poor inhibitor (Ki approximately 7.5 mM) of the mammalian aspartic acid protease pepsin. X-ray crystallographic studies at pH 4.2 show that the interactions of Glu at P2 and Leu at P1 of Glu-Asp-Leu with residues of the active site of HIV-1 protease are similar to those of other product-enzyme complexes. It was not feasible to understand the interaction of intact TFP with HIV-1 protease under conditions of crystal growth due to its hydrolysis giving rise to two products. The sequence-specific, selective inhibition of the HIV-1 protease by the viral TFP suggests a role for TFP in regulating protease function during HIV-1 replication.     

Craniofacial electromyogram activation response: another indicator of anesthetic depth

The female gametophyte is an absolutely essential structure for angiosperm reproduction. It produces the egg cell and central cell (which give rise to the embryo and endosperm, respectively) and mediates several reproductive processes including pollen tube guidance, fertilization, the induction of seed development, and perhaps also maternal control of embryo development. Although much has been learned about these processes at the cytological level, specific molecules mediating and controlling megagametogenesis and female gametophyte function have not been identified. A genetic approach to the identification of such molecules has been initiated in Arabidopsis and maize. Although genetic analyses are still in their infancy, mutations affecting female gametophyte function and specific steps of megagametogenesis have already been identified. Large-scale genetic screens aimed at identifying mutants affecting every step of megagametogenesis and female gametophyte function are in progress; the characterization of genes identified in these screens should go a long way toward defining the molecules that are required for female gametophyte development and function.     

On the many faces of Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.     

Acidic FGF regulation of hyperproliferation of fibroblasts in human autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cystic tubule enlargement and expansion of the interstitium associated with fibrosis. Our previous studies have analyzed the increased proliferation of cystic epithelial cells and this study examines the basis of increased proliferation of interstitial fibroblasts associated with ADPKD disease progression. ADPKD fibroblasts show phenotypic alterations in vitro, have acquired the capacity to grow in soft agar, and show an increased mitogenic response to a variety of growth factors particularly acidic FGF (aFGF). ELISA, Western immunoblot analysis, and immunocytochemistry showed increased aFGF content in ADPKD tissues and fibroblasts in culture, and aFGF was secreted into the extracellular matrix and conditioned medium, respectively. No alterations in aFGF receptor number were found, but Scatchard analysis of 125I-aFGF binding suggested an increased affinity of binding to the low affinity receptor, and covalent cross-linking analysis suggested the presence of novel putative receptors (120 kDa) in ADPKD fibroblasts. Signaling abnormalities were found, since aFGF incubation resulted in the tyrosine phosphorylation of additional substrates, more rapidly and for a more sustained duration in ADPKD fibroblasts than in normal fibroblasts. These findings suggest an important role for acidic FGF in the hyperproliferation of interstitial fibroblasts associated with disease progression in human ADPKD.     

Prolonged hypoxia increases vascular endothelial growth factor mRNA and protein in adult mouse brain

Brain hypoxia induces an increase in brain vascularity, presumably mediated by vascular endothelial growth factor (VEGF), but it is unclear whether VEGF is required to maintain the increase. In these studies, brain VEGF mRNA and protein levels were measured in adult mice kept in hypobaric chambers at 0.5 atm for 0, 0.5, 1, 2, 4, 7, and 21 days. Hypoxia was accompanied by a transient increase of VEGF mRNA expression: twofold by 0.5 day and a maximum of fivefold by 2 days; these were followed by a decrease at 4 days and a return to basal levels by 7-21 days. VEGF protein expression induced by hypoxia was bimodal, initially paralleling VEGF mRNA. There was an initial small increase at 12 h that reached a maximum by day 2, and, after a transient decrease on day 4, the protein expression increased again on day 7 before it returned to normoxic levels after 21 days. Thus, despite continued hypoxia, both VEGF mRNA and protein levels returned to basal after 7 days. These data suggest a metabolic negative-feedback system for VEGF expression during prolonged hypoxia in the brain.     

Catecholamine responses to short-term high-intensity resistance exercise overtraining

Seventeen weight-trained males were divided into an overtraining group [OT; n = 11; age = 22.0 +/- 0.9 (SE) yr] that weight trained their legs daily for 2 wk with 100% 1 repetition maximum relative intensity on a squat machine and a control group (n = 6; age = 23.7 +/- 2.4 yr) that exercised 1 day/wk with low relative intensity (50% 1 repetition maximum). Test batteries including strength assessments and resting and exercise-induced concentrations of epinephrine and norepinephrine were conducted at the beginning, middle, and end (tests 1-3, respectively) of the study. Strength capabilities decreased by test 3 for the OT group (P < 0.05). Resting catecholamine concentrations did not change for either group during the study, whereas exercise-induced concentrations of both epinephrine (test 1 = 3,407.9 +/- 666.6 pmol/l, test 2 = 7,563.7 +/- 1,210.6 pmol/l, test 3 = 6,931.6 +/- 919.3 pmol/l) and norepinephrine (test 1 = 42.9 +/- 7.4 nmol/l, test 2 = 70.0 +/- 8.8 nmol/l, test 3 = 85.2 +/- 14.5 nmol/l) significantly increased by tests 2 and 3 for only the OT group. Correlation coefficients suggested decreased responsitivity of skeletal muscle to sympathetic nervous system activity. It appears that altered exercise-induced sympathetic nervous system activity accompanies high relative intensity resistance exercise overtraining and may be among the initial responses to the onset of the previously theoretical sympathetic overtraining syndrome.