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Biomedical subjects

H Perkins

Publications and source records attributed to H Perkins.

At least 19 recordsLinked to original sources
PubMed2003

Sequence mapping of the Californian MSW strain of Myxoma virus.

Partial sequence mapping of the MSW Californian strain of Myxoma virus was performed by cloning EcoRI and SalI restriction fragments of viral DNA and sequencing the ends of these. In this way, regions of 74 MSW open reading frames were sequenced and mapped onto the complete genome sequences of the related leporipoxviruses South American Myxoma virus and Rabbit fibroma virus to form a partial map of the MSW strain. In general, gene locations and sequences were conserved between the three viruses. However the Californian Myxoma virus was more closely related to South American myxoma virus than to Rabbit fibroma virus based on sequence comparisons and the presence of three genes that have been lost from the Rabbit fibroma virus genome. Compared to the other two viruses, the main difference found in the MSW genome was that the terminal inverted repeats were extended with the duplication of 5 complete open reading frames (M151R, M152R, M153R, M154L, M156R) and partial duplication of one open reading frame (M150R). This rearrangement was associated with the loss of the majority of the M009L open reading frame. Three known virulence genes, including the serine proteinase inhibitor (SERPIN) genes M151R and M152R and leukemia associated protein (LAP) gene M153R, and the potential virulence gene M156R are now present in two copies.

Animals↗
PubMed1993

Characterization of factors affecting the stability of frozen heparinized plasma.

The use of heparin rather than citrate as primary anticoagulant has been shown to significantly improve the initial activity, stability and recovery of factor VIII:C from human plasma, cryoprecipitates or factor VIII concentrates if the plasma was initially frozen at -80 degrees C and subsequently stored at this temperature. If frozen and stored at progressively warmer temperatures however, increasing amounts of insoluble protein aggregates, termed storage precipitates (SPs), were recovered in the thawed plasma and cryoprecipitate fractions. Plasma recovery by centrifugation at 7,000 g for 7 min [Method I (MI)], 2 x 10 min (MII) or 15 min (MIII) had little effect on SP formation after 1 month at any storage temperature. After 4 months at -20 degrees C, more SP was recovered from MIII plasma whereas at -40 degrees C, more SP was recovered from MI plasma. Also, the preparation method had little or no effect on factor VIII:C activity at equivalent storage times or temperatures. A trend towards improved factor VIII recoveries was noted at lower freezing and storage temperatures however. SP formation was associated with reduced fibrinogen levels in the recovered plasma without loss of antithrombin-III or increased fibrinopeptide-A. Western blots showed polymerization of A alpha or gamma-chains of fibrinogen. SP formation was reduced or eliminated with factor XIII inhibitors, antibody to the active factor XIII a subunit or adjustment of heparinized plasma to 5-10 mM sodium citrate before initial freezing and storage. Although plasma factor VIII:C recoveries were only slightly affected at these citrate concentrations under most conditions, its recovery in cryoprecipitates was substantially improved owing to the reduction or absence of SPs.

Blood Preservation↗
PubMed1990

Development of a heat-treated factor VIII/von Willebrand factor concentrate prepared from heparinized plasma.

A high yield, intermediate purity factor VIII concentrate derived from heparinized plasma has been developed which can be heat-treated at 60 degrees C, 68 degrees C or 80 degrees C/72 h to permit inactivation of viral contaminants which may be present. After cold reprecipitation of the heparinized cryoprecipitate (CRC), the resolubilized CRC precipitate was adjusted to 25-30 mg/ml protein and pH 6.35 +/- 0.1 and incubated for 1 h at 8 degrees C. After centrifugation to remove the precipitated fibrinogen and fibronectin, a factor VIII-rich supernatant can be recovered which contains greater than 500 units of VIII:C per liter of starting plasma (Method I product) at a purity of 1.5 U/mg protein. Adjusted to 50 mM glycine and pH 6.8, the product can be lyophilized and heat-treated at 60 degrees C/72 h without a significant loss of VIII:C activity. However, at 68 degrees C or 80 degrees C/72 h, temperatures now reported to be more effective in viral inactivation, the recoveries were reduced to 68 and 33% respectively. Significantly improved recoveries after heat-treatment (HT) at 68 degrees C or 80 degrees C/72 h were achieved if the 8 degrees C supernatant product was prepared by a modified procedure (Method II). This further reduces the fibrinogen content of the product while maintaining VIII:C yields greater than 500 U/l at a purity of 1.9 U/mg. When adjusted to 50 mM glycine and 1-2% (w/v) sucrose (pH 6.8), lyophilized and heat treated at 60 degrees C, 68 degrees C or 80 degrees C/72 h, the VIII:C recoveries of Method II product were 88-100%, 79-84% and 80-83% of pre-HT levels respectively. The yield of VIII:C was greater than 400 U/l at a purity of 1.6-1.4 U/mg at 1-2% (w/v) sucrose even after the severe heat-treatment at 80 degrees C. In addition, the von Willebrand factor multimers are similar in size and triplet pattern to those observed in routine cryoprecipitate preparations.

Chemical Precipitation↗
PubMed1990

Monitoring blood donors for HIV-2 infection by testing anti-HIV-1 reactive sera.

Anti-HIV-1 EIA tests currently used for screening blood donors in the United States are estimated to detect 55 to 91% of HIV-2 infections; Western blots for HIV-1 antibodies may be positive, negative or indeterminate with HIV-2-positive sera. We reasoned that we could exploit the cross-reactivity of the anti-HIV-1 EIA as a means to monitor the blood supply for the appearance of HIV-2 infected or co-infected persons, and thus decide if and when routine HIV-2 screening should be adopted. We tested 913 anti-HIV-1-reactive donor sera using an anti-HIV-2 screening EIA, with confirmation by an anti-HIV-2 env-peptide EIA and an anti-HIV-2 Western blot. These 913 sera were derived from anti-HIV-1 screening of approximately 242,000 donations over a three year period. No HIV-2 infections were identified. This approach may warrant adoption in blood centers serving populations with persons from countries where HIV-2 is prevalent.

Antigens, Viral↗
PubMed1989

The National Marrow Donor Program: how it works, accomplishments to date.

As the use of bone marrow transplantation increases, the lack of a suitable matched sibling donor for approximately 60% of patients is a growing problem. Recently, marrow transplantation has been done successfully using HLA-matched unrelated donors. In an effort to provide more donors, the National Marrow Donor Program (NMDP) was established. It involves 50 blood banks and 20 marrow transplant centers throughout the United States. More than 20,000 HLA-typed apheresis donors from these blood banks have agreed to be listed in the NMDP registry. A preliminary search for donors has been carried out for 1,116 patients. Donors suitably matched for HLA-A and B antigens were located for 99% of the patients.

Bone Marrow Transplantation↗
PubMed1989

Patterns of T lymphocyte changes with human immunodeficiency virus infection: from seroconversion to the development of AIDS.

CD4 and CD8 T lymphocytes of three groups of men infected by the human immunodeficiency virus (HIV) were examined twice yearly for 36 months to elucidate the temporal trends in T lymphocytes during infection. The three groups were 37 HIV seroconverters, 304 prevalent HIV seropositives remaining free of the acquired immunodeficiency syndrome (AIDS), and 69 men who developed AIDS during observation. Six months before seroconversion, CD4 levels were similar among HIV seroconverters and 356 seronegative controls. Within 18 months of seroconversion, mean CD4 levels fell to the level of the prevalent seropositives at study entry. From there, the rate of decline slowed. CD8 lymphocyte counts rose dramatically at seroconversion. Among AIDS-free prevalent seropositives, CD4 levels fell steadily over 36 months of observation. By contrast, CD8 cell levels rose slowly. Among men who developed AIDS, mean CD4 levels fell more rapidly again during the 18 months prior to diagnosis. CD8 cell levels remained elevated until 6-12 months before diagnosis, when they began to fall.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Clinical, immunologic, and serologic findings in men at risk for acquired immunodeficiency syndrome. The San Francisco Men's Health Study.

Forty-nine percent of homosexual/bisexual men were positive for antibody to the human immunodeficiency virus (HIV) in a population-based probability sample of 1034 single men recruited from San Francisco. All heterosexual men were negative. Among seropositive men, marked lymphadenopathy was present in 29%, and 16% had at least two other symptoms or signs suggestive of HIV infection. However, lymphadenopathy alone failed to indicate severity of immune impairment. The occurrence of two or more clinical signs and symptoms, except for marked lymphadenopathy, correlated with HIV infection, diminished skin test reactivity, and reduction in Leu 3a T cells. Twenty-nine percent of seropositive men had fewer than 400 absolute Leu 3a T helper cells per microliter (less than 0.4 X 10(9)/L). Seronegative homosexual/bisexual men did not differ from heterosexual men in any clinical or laboratory variables except for increased numbers of suppressor Leu 2a T suppressor cells per microliter.

Acquired Immunodeficiency Syndrome↗