Synthetic Envelope Research Articles

Physical and hydraulic properties of synthetic envelopes for subsurface drainage in Pakistan

Three imported and four local synthetic envelope materials were tested in the laboratory with upward flow permeameters to determine their physical properties and hydraulic performance. The base soil was taken from the site of the Fourth Drainage Project, Faisalabad, Pakistan. The performance parameters included ratios of gradient and hydraulic conductivity of the interface of envelope material and base soil and the discharge through the permeameter, which were evaluated against established particle-retention and filter criteria.

Characterization of T cell epitopes on the envelope glycoprotein of simian retrovirus 1 and 2 (SRV-1 and SRV-2) in several mouse strains

Various mouse strains were immunized with either SRV-1 or SRV-2 virus adsorbed on alum. Seven to 14 days later spleen cells were removed, and spleen cells were cultured with varying amounts of SRV-1 virus and SRV-2 virus, or varying amounts of selected SRV-1 and SRV-2 synthetic envelope peptides to determine their ability to initiate T cell proliferative responses. Our studies demonstrated that all mouse strains tested gave strong proliferative responses with SRV-2 virus. In contrast, SRV-1 virus induced T cell proliferative responses only in H-2 k mouse strains. This apparent major histocompatibility complex (MHC)-restriction of SRV-1 virus-induced T cell proliferation correlates with the increased pathogenicity of SRV-1 virus in rhesus monkeys. The SRV envelope peptide 233–249 which is shared by both SRV-1 and SRV-2 virus initiates strong proliferative responses in both SRV-1 and SRV-2 virus immunized mice. The SRV-2 envelope peptide 96–102 initiates significant proliferative responses in SRV-2 immunized mice, and constitutes both a T and B cell epitope. The SRV-2 envelope peptide 127–152 has a 70% homology with the C-terminal region of SRV-1 peptide 142–167. The ability of SRV-2 peptide 127–152 to initiate T cell proliferation in SRV-1 virus immunized mice and the failure of the SRV-1 peptide 142–162 to initiate proliferation suggests that the region encompassing residues 160–167 must represent a T cell epitope in mice immunized with SRV-1 virus.

Bioartificial organs.

Bioartificial organs combine the physical aspects of implantable prostheses with the biological advantages of organ transplantation. Enclosing live cells in a permselective, synthetic envelope avoids rejection by an immunoincompatible host while the geometric limitation of the closed polymer capsule prevents overgrowth of the transplanted material. As a tenet bioartificial organs widen the range of therapeutics based on the biological activity of cell transplants and open an alternative path to gene therapy.

Characterization of T‐ and B‐cell epitopes of a simian retrovirus (SRV‐2) envelope protein

Synthetic envelope peptides of a simian retrovirus (SRV-2) were used to define both T- and B-cell epitopes of the envelope protein. The SRV-2 peptide 100-106 specifically blocks rhesus anti-SRV-2 neutralizing antibody activity, and a peptide 100-106 keyhole limpet hemocyanin conjugate induces a strong antipeptide antibody response. SRV-2 peptide 100-106 and 233-249 induces good T-cell proliferation of murine spleen cells immunized with the SRV-2 virus. Thus, SRV-2 envelope peptide 100-106 represents both a T- and B-cell epitope, and peptide 233-249 a T-cell epitope.

Different B-cell responses to human T-cell lymphotropic virus type I (HTLV-I) envelope synthetic peptides in HTLV-I-infected individuals

HTLV-I (human T-cell lymphotropic virus type I) is the retrovirus related to two distinct diseases, adult T-cell leukemia/lymphoma (ATLL) and HTLV-I-associated myelopathy (HAM). We analyzed the difference in antibody activities against the viral protein and the difference in specificities of anti-HTLV-I envelope antibodies among HTLV-I-infected individuals from the same HTLV-I-endemic area using a HTLV-I-gag-env hybrid protein and HTLV-I-env-encoded synthetic peptides as antigens, respectively. The difference in the responses of IgG anti-HTLV-I envelope antibody production among HTLV-I-infected individuals was qualitative as well as quantitative. Sera from patients with HAM showed significantly higher activities of antibodies against HTLV-I-gag-env hybrid protein than sera from other HTLV-I-infected individuals including ATLL patients. The specificities of IgG anti-HTLV-I-envelope antibodies, tested on seven synthetic envelope peptides, were directed mainly against four sites, V1E7 (residues 97-111), V1E8 (191-209), and V1E9 (268-286) on gp46 and V1E1 (342-363) on gp21. Three of these sites were shown to be immunodominant T-cell sites in mice in our previous study. Whereas patients in all categories made antibodies specific for V1E1 and V1E8, only HAM patients made antibodies to the V1E7 and V1E9 epitopes, suggesting a qualitative difference in response. Whether this difference is of pathogenetic significance is not clear.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of the parameters of the Rice distribution

This paper deals with the problem of estimating the parameters of the Rice distribution. The distribution has applications in sonar and radar signal processing and a proper estimation procedure with associated confidence intervals is important. Using the sample second moment as an estimate of the second moment of the distribution, two techniques, viz., methods of moments and maximum likelihood are applied to synthetic envelope data of known signal-to-noise ratios, in order to estimate the parameter from different sample sizes. It is concluded that the sample second moment is an unbiased estimate of the theoretical second moment and for the signal-to-noise ratio parameter both methods work without any significant bias and satisfy the criterion of maximum efficiency. However, the method of moments is simpler, easier to apply and therefore recommended as the method of choice.

Thin synthetic envelope materials for subsurface drainage tubes

Thin synthetic envelope materials for use on subsurface drainage tubes installed in silty soils were tested in the laboratory and in the field. Four different envelopes out of nineteen tested in the laboratory were selected for experiments in situ. All four envelopes were successful in preventing soil from entering drain pipes while maintaining drainage rates greater than the design drainage rate of 10 mm/day.

Nature of synthetic envelope materials in subsurface drainage

Drain pipe envelopes can contribute to improve the function of a drainage system if certain requirements are fulfilled. Envelope experience shows decay of organic coconut fibre envelopes. The need for envelopes does not only depend on the clay content of the soil. The kind of envelope to use is still based on subjective criteria. Therefore, a model research study has been set up to evaluate the need for envelopes and their efficiency. From this research some preliminary directives about the nature of synthetic envelopes for subsurface drainage in agriculture are given.

Synthetic Drain Envelope—Soil Interactions

Synthetic drain envelope materials currently available commercially have been found to be equally effective as drain envelopes. The materials function primarily as mechanical support for the soil-drain opening interface. Soils have a limited characteristic resistance to internal hydraulic gradients. Flows causing gradients in excess of the hydraulic failure gradient of the particular soil will result in failure of the soil structural skeleton and the drain envelope.