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Biomedical subjects

R D Pearson

Publications and source records attributed to R D Pearson.

At least 37 records · Page 2Linked to original sources
PubMed1998

cDNA and deduced amino acid sequences of a peritrophic membrane glycoprotein, 'peritrophin-48', from the larvae of Lucilia cuprina.

The gut of most insects is lined with a semi-permeable peritrophic membrane (or peritrophic matrix) composed of chitin, proteoglycans and proteins. Despite the probable importance of the peritrophic membrane in facilitating the digestive process and protecting insects from invasion by micro-organisms and parasites, there has been little characterization of the specific components and their interactions within this acellular structure. Here we report the characterization of an integral peritrophic membrane glycoprotein, peritrophin-48, from the larvae of the fly Lucilia cuprina, a primary agent of cutaneous myiasis in sheep. Peritrophin-48 was purified from peritrophic membrane obtained by larval culture and its location within the peritrophic membrane determined by immuno-fluorescence and immuno-gold localizations. The cDNA coding for peritrophin-48 was cloned and sequenced. The deduced amino acid sequence codes for a protein of 375 amino acids containing an amino-terminal signal sequence followed by five similar, but non-identical domains, each approximately 65-70 amino acids in length and characterised by a specific register of six cysteines. The deduced amino acid sequence shows significant similarity to two other peritrophic membrane proteins, peritrophin-95 and peritrophin-44, from the same species. A reverse transcriptase-PCR approach indicated that there are several highly related peritrophin-48 genes expressed in each individual. Reverse transcriptase-PCR also demonstrated the expression of peritrophin-48 in all three larval instars and adults but not pupae or eggs. Peritrophin-48 was expressed only by the cardia and by the larval midgut. A simple structural model of a basic unit of a type 2 peritrophic membrane is presented.

Amino Acid Sequence↗
PubMed1998

Vaccination of cattle against the Boophilus microplus using a mucin-like membrane glycoprotein.

An antigen, BMA7, which induced partial immunity against tick infestation has been isolated from Boophilus microplus using two different protein fractionation protocols, accompanied by vaccination and parasite challenge trails. The antigen is a 63 kDa glycoprotein isolated from semi-engorged adult female ticks. Though significant, the induced immunity is less striking than that previously reported for antigen Bm86 from the same parasite. However, co-vaccination with Bm86 and BMA7 can enhance immunity over that seen with a commercial vaccine based on Bm86 alone. Limited peptide sequence information shows significant variation in the BMA7 protein occurs. The antigen has approximately 36 kDa of glycosylation, in both N-linked and O-linked oligosaccharides. There is evidence that both polypeptide and oligosaccharide are antigenic, but the chemical nature of the protective antigenic sites is not clear. There is little or no immunological response to the antigen during natural infestation with parasites, suggesting the antigen is 'concealed' and protective immunity dependent on artificial vaccination. The antigen has some similarities with the vertebrate mucins. It is widely distributed in tick tissues and membrane bound but its function is currently unknown.

Amino Acid Sequence↗
PubMed1998

Neurocysticercosis in Ceará State, northeastern Brazil: a review of 119 cases.

Relatively little is known about the occurrence of neurocysticercosis in northeastern Brazil. There have been no published reports from the state of Ceará, but a review of the records at the Hospital São José in Fortaleza, Brazil identified 119 patients with neurocysticercosis diagnosed between January 1988 and April 1994. Patients came from 43 municipalities in Ceará. Their ages ranged from five to 74 years; the greatest number of cases were in persons 10-40 years of age; 63% were males. Seizures were the presenting complaint in 64% of the patients and headache in 22%. Two patients, each with several hundred intracranial lesions, presented with mental status changes; one was initially given the clinical diagnosis of viral meningoencephalitis. Computed tomography scans showed that 44% of the patients had five or more lesions. Cysts were found throughout the brain. The parietal lobe was the most frequent site of involvement; 85% of patients had one or more lesions there. The brain stem was involved in 8%. There was no consistent association between the severity of the clinical abnormalities and the radiologic findings. Computed tomography of the thighs was done in 10 persons; cysts were identified in nine.

Adolescent↗
PubMed1997

Sporotrichoid cutaneous leishmaniasis in a traveler.

A 19-year-old construction worker from Virginia who had traveled in Bolivia had sporotrichoid lesions on the left arm. Only after unsuccessful therapy for sporotrichosis was a diagnosis of cutaneous leishmaniasis considered. Biopsies revealed necrotizing granulomatous changes, and culture of the biopsy specimens grew Leishmania (Viannia) braziliensis. The sporotrichoid pattern seen in this patient is a rare but recognized presentation of cutaneous leishmaniasis, more commonly seen in American cutaneous leishmaniasis than in Old World cutaneous leishmaniasis. This case illustrates the necessity of careful and early consideration of tropical infections in the differential diagnosis of disease in a traveler.

Adult↗
PubMed1996

Characterization of a major peritrophic membrane protein, peritrophin-44, from the larvae of Lucilia cuprina. cDNA and deduced amino acid sequences.

The peritrophic membrane is a semi-permeable chitinous matrix lining the gut of most insects and is thought to have important roles in the maintenance of insect gut structure, facilitation of digestion, and protection from invasion by microrganisms and parasites. Proteins are integral components of this matrix, although the structures and functions of these proteins have not been characterized in any detail. The peritrophic membrane from the larvae of the fly Lucilia cuprina, the primary agent of cutaneous myiasis in sheep, was shown to contain six major integral peritrophic membrane proteins. Two of these proteins, a 44-kDa glycoprotein (peritrophin-44) and a 48-kDa protein (peritrophin-48) together represent >70% of the total mass of the integral peritrophic membrane proteins. Peritrophin-44 was purified and its complete amino acid sequence was determined by cloning and sequencing the DNA complementary to its mRNA. The deduced amino acid sequence codes for a protein of 356 amino acids containing an amino-terminal signal sequence followed by five similar but nonidentical domains, each of approximately 70 amino acids and characterized by a specific register of 6 cysteines. One of these domains was also present in the noncatalytic regions of chitinases from Brugia malayi, Manduca sexta, and Chelonus. Peritrophin-44 has a uniform distribution throughout the larval peritrophic membrane. Reverse transcriptase-polymerase chain reaction detected the expression of peritrophin-44 in all three larval instars but only trace levels in adult L. cuprina. The protein binds specifically to tri-N-acetyl chitotriose and reacetylated chitosan in vitro. It is concluded that the multiple cysteine-rich domains in peritrophin-44 are responsible for binding to chitin, the major constituent of peritrophic membrane. Peritrophin-44 probably has roles in the maintenance of peritrophic membrane structure and in the determination of the porosity of the peritrophic membrane. This report represents the first characterization of an insect peritrophic membrane protein.

Amino Acid Sequence↗
PubMed1996

Effect of mitonafide analogs on topoisomerase II of Leishmania chagasi.

Mitonafide (4-nitro-benzoisoquinolinedione) and a number of structural analogs were synthesized and studied in order to determine the structural requirements for inhibition of leishmanial nuclear and kinetoplast topoisomerase II and human topoisomerase II. The structure-activity relationship studies with the mitonafide analogs demonstrated that there was selective targeting of leishmanial nuclear topoisomerase II and human topoisomerase II and differential targeting of kinetoplast over nuclear topoisomerase II in the parasite. Mitonafide analogs appeared to have multiple mechanisms of action leading to death of leishmanias, but several compounds that affected kinetoplast but not nuclear topoisomerase II were not cytotoxic as determined by short-term assays. These studies provide new insight into the differential sensitivities of leishmanial nuclear and kinetoplast topoisomerase II to topoisomerase II-targeting drugs.

Animals↗
PubMed1995

Carboxydipeptidase from Boophilus microplus: a "concealed" antigen with similarity to angiotensin-converting enzyme.

A protein, Bm91, which was first identified as a protective vaccine antigen from the tick Boophilus microplus, has regions of very strong amino acid sequence similarity to mammalian carboxydipeptidases or angiotensin converting enzymes (ACE; E.C. 3.4.15.1). This protein is now shown to share many biochemical and enzymatic properties with mammalian carboxydipeptidases. It is enzymatically active in a conventional assay for ACE using hippuryl-Gly-Gly as substrate. The hydrolysis of the C-terminal nonapeptide of the insulin B chain proceeds by sequential removal of carboxy-terminal dipeptides. The similarities extend to the dependence of activity on pH and added salt. Bm91 is inhibited by two well-characterized inhibitors of the mammalian enzymes, the drug Captopril and a nonapeptide, and the inhibition occurs in similar concentration ranges to those effective with the mammalian enzymes. However, the natural substrates of the tick enzyme are unknown. Angiotensin I itself is a poor substrate and the enzyme's natural substrates are likely to be one or more of the pharmacologically active peptides occurring in insects and arthropods.

Amino Acid Sequence↗
PubMed1995

Identification of Leishmania chagasi antigens recognized by human lymphocytes.

Preparative SDS-PAGE followed by electroelution was used to separate proteins of Leishmania chagasi promastigotes into 67 fractions. These fractions were tested for the ability to stimulate proliferation of peripheral blood mononuclear cells from healthy immune donors who were treated previously for visceral leishmaniasis and from nonimmune controls. The proliferative responses elicited by these proteins varied among individuals. The 69-kDa protein fraction contained a fragment with sequence similarity to the 70-kDa heat-shock protein. Fragments of the 46- and 41-kDa fractions had sequences not present in the National Biological Research Foundation data bank. These data suggest that a successful subunit vaccine may require multiple parasite antigens. The identification of antigens that elicit human T cell responses is an important step toward understanding the immunology of L. chagasi infection and ultimately in the development of a vaccine.

Amino Acid Sequence↗
PubMed1995

Short report: extended follow-up of the natural history of persons infected with Leishmania chagasi.

A five-year follow-up of the natural history of 924 children exposed to or infected with Leishmania chagasi was conducted in a rural area of northeast Brazil. Seventy-eight percent of the children sought were located. There was no evidence of smoldering disease or long subclinical latency in this population. The overall prevalence of clinical visceral leishmaniasis in this population was 6.1%, with a mortality rate of 10%.

Adolescent↗
PubMed1994

Ingestion of host antibodies by Bovicola ovis on sheep.

Sheep body lice, Bovicola ovis, collected from moderately heavy infestations on Merino wethers, were assayed by ELISA for their content of host-derived specific immunoglobulin (Ig). Relative concentrations of anti-horse myoglobin antibodies in the lice and in sera from their hosts were used to estimate the total quantities of functional Ig (that which remained capable of binding specifically to its antigen) present, giving a mean of 0.21 +/- 0.20 mg/g of lice. An attempt to demonstrate the presence of antibodies against B. ovis antigens in naturally-infested host sheep using ELISA produced inconclusive results. The implications of the quantities of Ig ingested by feeding B. ovis are discussed in relation to the feasibility of immunological control of this species on sheep.

Animals↗