Submandibular salivary proteases: lack of a role in anti-HIV activity

Whole human saliva contains a number of proteolytic enzymes, mostly derived from white blood cells and bacteria in the oral cavity. However, less information is available regarding proteases produced by salivary glands and present in salivary secretions. In the present study, we have analyzed submandibular saliva, collected without contaminating cells, and identified multiple proteolytic activities. These have been characterized in terms of their susceptibility to a series of protease inhibitors. The submandibular saliva proteases were shown to be sensitive to both serine and acidic protease inhibitors. We also used protease inhibitors to determine if salivary proteolytic activity was involved in the inhibition of HIV infectivity seen when the virus is incubated with human saliva. This anti-HIV activity has been reported to occur in whole saliva and in ductal saliva obtained from both the parotid and submandibular glands, with highest levels of activity present in the latter fluid. Protease inhibitors, at concentrations sufficient to block salivary proteolytic activity in an in vitro infectivity assay, did not block the anti-HIV effects of saliva, suggesting that the salivary proteases are not responsible for the inhibition of HIV-1 infectivity.     

Resource allocation and resident outcomes in nursing homes: comparisons between the best and worst

This article examines ethical dilemmas related to cochlear implant surgery in children. These dilemmas arise from the existence of a linguistic and cultural minority called the Deaf World. Organizations of culturally Deaf adults in the United States and abroad, as well as the World Federation of the Deaf, have, on ethical grounds, strongly criticized the practice of cochlear implant surgery in children. Three ethical dilemmas are examined. (1) The surgery is of unproven value for the main significant benefit sought, language acquisition, whereas the psychological, social, and linguistic risks have not been assessed. Thus the surgery appears to be innovative, but innovative surgery on children is ethically problematic. (2) It is now widely recognized that the signed languages of the world are full-fledged natural languages, and the communities that speak those languages have distinct social organizations and cultures. Deaf culture values lead to a different assessment of pediatric cochlear implant surgery than do mainstream (hearing) values, and both sets of values have standing. (3) The fields of otology and audiology want to provide cochlear implants to Deaf children but also, their leaders say, want to protect Deaf culture; those appear to be conflicting goals in principle because, if there were perfect implants, the ranks of the Deaf World would diminish.     

Surgical outcomes using bioabsorbable plating systems in pediatric craniofacial surgery

The purpose of this study was to evaluate the surgical outcomes of the 1.5-mm LactoSorb plating system (Walter Lorenz Surgical, Inc., Jacksonville, FL, U.S.A.) used to stabilize the osteotomized calvarial bone in pediatric patients who have undergone craniofacial surgery. The records of 33 consecutive pediatric patients who underwent craniofacial surgery from January 1997 through December 1997 were reviewed. There were 18 male and 15 female patients, and the age ranged from 4 months to 12 years. Patients were followed-up at 1 week, 1 month, 3 months, 6 months, and 12 months after surgery. For those patients reviewed, the following information is included: age, sex, diagnosis, surgical procedures, number and size of LactoSorb plates and screws used in each patient, operative difficulty of the screws and the heat pack, and postoperative complications, including wound healing, palpability, and infection. The LactoSorb plating system was used to stabilize the osteotomized calvarial bones in 33 patients who were diagnosed with: 1) craniosynostosis, 2) hydrocephalus, 3) fibrous dysplasia, or 4) cranial deformation. Orbital rim advancement and anterior cranial vault reshaping were performed in 17 patients. Posterior cranial vault reshaping, orbital rim advancement, and anterior cranial vault reshaping were performed in eight patients. Posterior cranial vault reshaping only was performed in seven patients. Excision of fibrous dysplasia from temporal bone was performed in one patient. One patient had a postoperative wound infection, and LactoSorb plates were palpable postoperatively in four patients. The LactoSorb plating system provided adequate rigidity for stabilizing the osteotomized calvarial bone during surgery and maintained adequate rigidity after surgery during the bone healing period before absorption. This plating system showed satisfactory results in pediatric craniofacial surgery patients.     

Extraskeletal osteosarcoma of the hand. A case report

T cell mediated autoimmunity may be important in inflammatory skin disease, but target autoantigens have not previously been described. In studies aimed at defining T cell epitopes, aqueous extracts of normal facial and plantar stratum corneum have consistently been found to induce potent proliferation of peripheral blood mononuclear cells from normal donors and patients with inflammatory skin disease, giving stimulation indices up to 80. Potent stimulation was seen with both autologous and allogeneic stratum corneum extracts. Because of the presence of inhibitory material, demonstration of the stimulatory activity was critically dependent on extract concentration, and was facilitated by short-term pulsing of cultures with extract. The proliferation of cells purified from peripheral blood mononuclear cells by immunomagnetic beads and immunophenotyping of cell lines generated from peripheral blood mononuclear cells, confirmed the T cell nature of the response to stratum corneum extracts. The activity was inhibited by HLA-DR monoclonal antibody, indicating the presence of antigen or superantigen. Tetanus toxoid reactive clones and a purified protein derivative reactive line failed to respond to the stratum corneum extracts, indicating that the active material is not a nonspecific T cell stimulant such as a cytokine or mitogen. This and the failure of recombinant interleukin-1alpha to stimulate peripheral blood mononuclear cells in concentrations up to 1000 U per ml, indicate that the activity is not due to interleukin-1. We propose the hypothesis that antigenic or superantigenic material is normally sequestered from the immune system in the epidermis, but induces T cell activation when released following wounding and in disease, and that this represents an important and previously unrecognized pathogenic mechanism.     

The recognition of sentences in noise by normal-hearing listeners using simulations of cochlear-implant signal processors with 6-20 channels

Sentences were processed through simulations of cochlear-implant signal processors with 6, 8, 12, 16, and 20 channels and were presented to normal-hearing listeners at +2 db S/N and at -2 db S/N. The signal-processing operations included bandpass filtering, rectification, and smoothing of the signal in each band, estimation of the rms energy of the signal in each band (computed every 4 ms), and generation of sinusoids with frequencies equal to the center frequencies of the bands and amplitudes equal to the rms levels in each band. The sinusoids were summed and presented to listeners for identification. At issue was the number of channels necessary to reach maximum performance on tests of sentence understanding. At +2 dB S/N, the performance maximum was reached with 12 channels of stimulation. At -2 dB S/N, the performance maximum was reached with 20 channels of stimulation. These results, in combination with the outcome that in quiet, asymptotic performance is reached with five channels of stimulation, demonstrate that more channels are needed in noise than in quiet to reach a high level of sentence understanding and that, as the S/N becomes poorer, more channels are needed to achieve a given level of performance.     

NIDDM genes in mice: deleterious synergism by both parental genomes contributes to diabetogenic thresholds

We used mouse genetics to model how polygenic thresholds for the transition from impaired glucose tolerance (IGT) to NIDDM are reached. NON/Lt and NZO/Hl are inbred mouse strains selected for IGT and polygenic obesity, respectively. Their F1 male progeny consistently developed NIDDM. Genetic analysis of F2 males from both cross directions identified an NON-derived diabetogenic locus, Nidd 1, on chromosome (Chr) 4 near the leptin receptor. This locus was associated with reduced plasma insulin, increased non-fasted blood glucose, and lower body weight. Another NON-derived diabetogenic locus on Chr 18 (Nidd2) that controls blood glucose was identified. An NZO-derived diabetogenic region on Chr 11 (Nidd3), possibly comprising two separate loci, reduced ability to sustain elevated plasma insulin and significantly reduced weight gain over time. Thus, the diabetogenic synergism between genetic loci from strains separately exhibiting subthreshold defects perturbing glucose homeostasis underscores the likely complexity of the inheritance of obesity-associated forms of NIDDM in humans.     

Insights into the mechanism of catalysis by the P-C bond-cleaving enzyme phosphonoacetaldehyde hydrolase derived from gene sequence analysis and mutagenesis

Phosphonoacetaldehyde hydrolase (phosphonatase) catalyzes the hydrolysis of phosphonoacetaldehyde to acetaldehyde and inorganic phosphate. In this study, the genes encoding phosphonatase in Bacillus cereus and in Salmonella typhimurium were cloned for high-level expression in Escherichia coli. The kinetic properties of the purified, recombinant phosphonatases were determined. The Schiff base mechanism known to operate in the B. cereus enzyme was verified for the S. typhimurium enzyme by phosphonoacetaldehyde-sodium borohydride-induced inactivation and by site-directed mutagenesis of the catalytic lysine 53. The protein sequence inferred from the B. cereus phosphonatase gene was determined, and this sequence was used along with that from the S. typhimurium phosphonatase gene sequence to search the primary sequence databases for possible structural homologues. We found that phosphonatase belongs to a novel family of hydrolases which appear to use a highly conserved active site aspartate residue in covalent catalysis. On the basis of this finding and the known stereochemical course of phosphonatase-catalyzed hydrolysis at phosphorus (retention), we propose a mechanism which involves Schiff base formation with lysine 53 followed by phosphoryl transfer to aspartate (at position 11 in the S. typhimurium enzyme and position 12 in the B. cereusphosphonatase) and last hydrolysis at the imine C(1) and acyl phosphate phosphorus.     

The many faces of pulmonary aspiration

The population pharmacokinetics of nevirapine (NVP), zidovudine (ZDV), and didanosine (ddI) were evaluated in a total of 175 patients infected with human immunodeficiency virus randomized to receive either a double combination of ZDV plus ddI or a triple combination of NVP plus ZDV plus ddI as a substudy of the AIDS Clinical Trials Group Protocol 241. Levels (approximating 3.5 determinations/patient) of the three drugs in plasma were measured during 44 of a total 48 weeks of study treatment, and a set of potential covariates was available for nonlinear mixed-effect modeling analysis. A one-compartment model with zero-order input and first-order elimination was fitted to the NVP data. Individual oral clearance (CL) and volume of distribution (V) averaged 0.0533 liters/h/kg of body weight and 1.17 liters/kg, respectively. Gender was the only covariate which significantly correlated with the CL of NVP. ZDV and ddI data were described by a two-compartment model with zero-order input and first-order elimination. Individual mean oral CL, VSS (volume of distribution at steady state), and V of ZDV were 1.84 liters/h/kg and 6.68 and 2.67 liters/kg, respectively, with body weight and age as correlates of CL and body weight as a correlate of VSS. The average individual oral CL, VSS, and V of ddI were 1.64 liters/h/kg and 3.56 and 2.74 liters/kg, respectively, with body weight as a significant correlate of both CL and VSS. The relative bioavailability (F) of ZDV and ddI in the triple combination compared to that in the double combination was also evaluated. No significant effects of the combination regimens on the F of ddI were detected (FTRIPLE = 1.05 and FDOUBLE = 1 by definition), but the F of ZDV was markedly reduced by the triple combination, being only 67.7% of that of the double combination. Large (>50%) intraindividual variability was associated with both ZDV and ddI pharmacokinetics. Individual cumulative area under the plasma drug level-time curve of the three drugs was calculated for the entire study period as a measure of drug exposure based on the individual data and the final-model estimates of structural and statistical parameters.