David Humber - Academia.edu (original) (raw)

Papers by David Humber

Research paper thumbnail of Antibacterial activity of plants used in traditional medicines of Ghana with particular reference to MRSA

Journal of Ethnopharmacology, 2008

Ethnopharmacological relevance: : In an ethno botanical survey carried out in the Akwapim-North d... more Ethnopharmacological relevance: : In an ethno botanical survey carried out in the Akwapim-North district of the Republic of Ghana, 25 plant species, used in traditional medicine to treat skin disease and/or to treat antimicrobial (viral, bacterial or protozoan) infections were identified. Aim of Study: : To investigate the antimicrobial activity of traditional Ghanaian medicines with special interest in anti-methicillin-resistant Staphylococcus aureus (MRSA) activity. Materials and methods: : Chloroform, ethanol and aqueous extracts (including use of a Stomacher) of these plants were prepared and agar-well diffusion tests, MIC's and MBC's were used to investigate antimicrobial activity. Results: Extracts of 13 plant species inhibited the growth of one or more of the following bacteria: MRSA, methicillin-sensitive Staphylococcus aureus (MSSA), Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris. Extracts from 11 of these 13 plant species also inhibited the growth of three or more of 14 additional clinical isolates of MRSA. Aqueous extracts of Alchornea cordifolia were active against all 21 bacterial strains tested and showed the highest levels of antibacterial activity overall with MIC's against MRSA in the range of 1.6-3.1 mg ml −1 and MBC's in the range of 6.3-12.5 mg ml −1. Conclusions: : The presence of antibacterial activity in extracts of Elaeophorbia drupifera, Rauwolfia vomitoria and the leaves of Solanum verbascifolium, plants traditionally used to treat skin infections, are reported for the first time. Extracts from Alchornea cordifolia, also used to treat wounds, had the widest spectrum of antibacterial activity.

Research paper thumbnail of Non-specific cell mediated immunity in patients infected with Schistosoma mansoni in Kenya

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1982

Parameters of in vitro cell-mediated immunity (CMI) have been measured in the local Kenyan oooula... more Parameters of in vitro cell-mediated immunity (CMI) have been measured in the local Kenyan oooulation infected with Schistosoma mansoni. Lvmphbcyte responses to the non-specific T cell mitogens Concanavalin A (Con A) and Phytohaemagglutinin (PHA) were reduced in about 60% of schistosomiasis patieits. Lymphocytes from control uninfected, and S. mansoni-infected donors formed equal numbers of spontaneous rosettes with sheep red blood cells, indicating that there was no overall reduction in the percentage numbers of T cells in the schistosomiasis patients.

Research paper thumbnail of Birds on Lake Shala islands, 6 August 1988

Research paper thumbnail of The Effects of Pregnancy on the Immunological Competence of Congenitally Athymic (Nude) Mice

Research paper thumbnail of The effect of cicerfuran, related arylbenzofuransand stilbenes on Leishmania aethiopica, L. tropica, and L. major promastigotes

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2003

insecticide-treated nets (ITN) are a key strategy for malaria control in Ghana. However, little i... more insecticide-treated nets (ITN) are a key strategy for malaria control in Ghana. However, little is known about the species composition and insecticide susceptibility of vector populations. This paper presents an initial survey of the distribution of molecular forms of Anopheles gambiae and insecticide resistance (the kdr mutation) from 579 mosquitoes collected from 8 sites in 2 ecological zones in southern Ghana. The molecular Plasma vitamin A and E levels of HIV-infected and HIV-uninfected Zambian women during pregnancy and lactation

Research paper thumbnail of The Effect of Cicerfuran, an Arylbenzofuran fromCicer bijugum, and Related Benzofurans and Stilbenes onLeishmania aethiopica,L.tropicaandL.major

Research paper thumbnail of Genetic and Immunological Aspects of Litter Size in the Mouse

European Journal of Immunogenetics, 1976

The effects of antigenic differences between mother and fetus on implantation number and on post-... more The effects of antigenic differences between mother and fetus on implantation number and on post-implantation mortality were studied. No evidence was found to support the hypothesis that these two measurements were affected by such antigenic differences or by prior immunization of the mother to paternal antigens. I N T R O D U C T I O N Litter size at birth is a complex characteristic, and is dependent on four major factors each of which determines the upper numerical limits of the next: (1) The number of ova shed. (2) The number of ova fertilized. (3) The number of blastocysts that successfully implant. (4) The number of implanted blastocysts which develop to term.

Research paper thumbnail of The Effect of Pregnancy on Lymph Node Weight in the Mouse

International Journal of Immunogenetics, 1977

SUMMARYLumbar and renal lymph nodes, inguinal lymph nodes and spleen weights were recorded during... more SUMMARYLumbar and renal lymph nodes, inguinal lymph nodes and spleen weights were recorded during pregnancy in mice after mating with males of the same (syngeneic) or a different (allogeneic) strain. The weights of these nodes increased during pregnancy. Spleen weights increased up to the fifteenth day of pregnancy and then decreased in weight. There was no consistent correlation of any of these measurements with the extent of the antigenic dissimilarity between mother and conceptus.

Research paper thumbnail of Leishmanicidal Activity of Yucatecan Medicinal Plants on Leishmania Species Responsible for Cutaneous Leishmaniasis

Journal of Parasitology, 2009

Research paper thumbnail of Interaction between Leishmania parasites and mammalian macrophages

Research paper thumbnail of An immunosuppressive factor in the serum of patients with schistosomiasis

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1980

Research paper thumbnail of Demonstration of mycobacterial antigens in nerve biopsies from leprosy patients using peroxidase-antiperoxidase immunoenzyme technique

Clinical immunology and …, 1983

Peripheral nerve biopsies from patients with leprosy were stained with anti-Mycobacterium bovis (... more Peripheral nerve biopsies from patients with leprosy were stained with anti-Mycobacterium bovis (BCG) in a peroxidase-antiperoxidase (PAP) system to demonstrate intraneural mycobacterial antigens. Most M. leprae antigens have been shown to crossreact with BCG ...

Research paper thumbnail of The Influence of Parity and Maternal Preimmunization on Fetal Survival in Mice

Reproduction, 1974

A common immunological consequence of pregnancy is that the mother may become sensitized to fetal... more A common immunological consequence of pregnancy is that the mother may become sensitized to fetal or paternal antigens (Goodlin & Herzenberg, 1964; Kaliss & Dagg, 1964; Soren, 1967). Recently, Maroni & Parrott (1973) have demonstrated that cell-mediated immunity against paternal antigens increases with parity. We have attempted to compare the results of normal parity with artificial immunization designed to simulate maternal sensitization to paternal antigens.

Research paper thumbnail of Fetal Wastage as a Consequence of Mycoplasma Pulmonis Infection in Mice

Reproduction, 1975

The effect of Mycoplasma pulmonis, strain JB, on the outcome of pregnancy in TO mice was studied.... more The effect of Mycoplasma pulmonis, strain JB, on the outcome of pregnancy in TO mice was studied. The mice were infected intravenously before or after mating and the fetuses were examined at autopsy just before parturition. An increase in the number of abnormal pregnancies was noted in mice infected about 2 weeks before mating, and there was a significant increase in the number of fetuses which died midway through pregnancy. Mycoplasmas were not isolated from any of the fetuses although the organisms reached the joints of the pregnant mice and caused arthritis. It is possible, therefore, that maternal upset was a factor in these abnormal pregnancies. In mice infected at various times after mating, abnormal pregnancies were most frequently seen in those infected 9 days after mating. There was an increase in the number of both mid-and late-stage fetal deaths in these mice and also an increase in the number of late-stage fetal deaths in mice infected 5 days after mating. Mycoplasmas were isolated not only from most ofthe dead fetuses but also from living ones which suggests that in most instances death was probably due to maternal infection and disturbance rather than fetal infection per se. The possibility of modifying this mouse model by establishing a chronic genital tract infection is discussed as a means of investigating the r\l=o^\leof mycoplasmas in human abortion.

Research paper thumbnail of The Effects of Active Immunization on the Decidual Cell Reaction and Ectopic Blastocyst Development in Mice

Reproduction, 1975

One of the most striking features of early pregnancy in the mouse is the development of the decid... more One of the most striking features of early pregnancy in the mouse is the development of the decidual cell reaction (DCR). This cellular proliferation

Research paper thumbnail of Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites?

Parasitology, 2008

SUMMARYLeishmania parasites invade host macrophages, causing infections that are either limited t... more SUMMARYLeishmania parasites invade host macrophages, causing infections that are either limited to skin or spread to internal organs. In this study, 3 species causing cutaneous leishmaniasis, L. major, L. aethiopica and L. tropica, were tested for their ability to interfere with apoptosis in host macrophages in 2 different lines of human monocyte-derived macrophages (cell lines THP-1 and U937) and the results confirmed in peripheral blood mononuclear cells (PBMC). All 3 species induced early apoptosis 48 h after infection (expression of phosphatidyl serine on the outer membrane). There were significant increases in the percentage of apoptotic cells both for U937 and PBMC following infection with each of the 3 species. Early apoptotic events were confirmed by mitochondrial membrane permeabilization detection and caspase activation 48 and 72 h after infection. Moreover, the percentage of infected THP-1 and U937 macrophages increased significantly (up to 100%) following treatment with ...

Research paper thumbnail of Leishmania aethiopica: Infections in laboratory animals

Experimental Parasitology, 1989

Leishmania aethiopica parasites were inoculated into 11 different strains and species of small la... more Leishmania aethiopica parasites were inoculated into 11 different strains and species of small laboratory animals. Clinical lesions were only produced following inoculation of hamster noses and thus this parasite is highly selective in both species and site for the laboratory animals tested. Parasites could, however, be recovered from draining lymph nodes 3 weeks after infection of BALB/c mice. Lesions in hamsters were progressive and nonulcerating (up to 1 year) and histologically resembled diffuse cutaneous leishmaniasis (DTH) in man. Pronounced delayed hypersensitivity responses to L. aethiopica antigens only developed in mice despite the absence of clinical lesions. Weak DTH responses were produced in hamsters with clinical lesions only after 25 weeks of infection.

Research paper thumbnail of Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites

Research paper thumbnail of Cutaneous leishmaniasis in south-western Ethiopia: Ocholo revisited* 1

Transactions of the …, 1992

The borough of Ocholo, on the western side of the Ethiopian Rift Valley, is an endemic focus for ... more The borough of Ocholo, on the western side of the Ethiopian Rift Valley, is an endemic focus for Leishmania aethiopica infection and has been surveyed thrice between 1987 and 1990. In 1989,3022 inhabitants (>95% of the population) were interviewed and examined. The overall prevalence of localized cutaneous leishmaniasis (LCL) was 36-+0%, with a peak value of 8.5% in the O-10 years old age group. In half of the patients the active disease was estimated to last for 9.6*6 months; in lo%, it exceeded 3 years. Scars of LCL were present in 34.3% of the residents. Leishmanin skin tests were positive in 54% of 120 school-children without signs of the disease. Therefore, in Ocholo a minimum of 71.6% of the population has been exposed to L. aethiopica infection. Two cases of the diffuse form of cutaneous leishmaniasis were observed. In this highland biotope, Phlebotomus pedifer was found to be the major, and possibly the only, vector for L. aethiopica.

Research paper thumbnail of Antibacterial activity of plants used in traditional medicines of Ghana with particular reference to MRSA

Journal of Ethnopharmacology, 2008

Ethnopharmacological relevance: : In an ethno botanical survey carried out in the Akwapim-North d... more Ethnopharmacological relevance: : In an ethno botanical survey carried out in the Akwapim-North district of the Republic of Ghana, 25 plant species, used in traditional medicine to treat skin disease and/or to treat antimicrobial (viral, bacterial or protozoan) infections were identified. Aim of Study: : To investigate the antimicrobial activity of traditional Ghanaian medicines with special interest in anti-methicillin-resistant Staphylococcus aureus (MRSA) activity. Materials and methods: : Chloroform, ethanol and aqueous extracts (including use of a Stomacher) of these plants were prepared and agar-well diffusion tests, MIC's and MBC's were used to investigate antimicrobial activity. Results: Extracts of 13 plant species inhibited the growth of one or more of the following bacteria: MRSA, methicillin-sensitive Staphylococcus aureus (MSSA), Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris. Extracts from 11 of these 13 plant species also inhibited the growth of three or more of 14 additional clinical isolates of MRSA. Aqueous extracts of Alchornea cordifolia were active against all 21 bacterial strains tested and showed the highest levels of antibacterial activity overall with MIC's against MRSA in the range of 1.6-3.1 mg ml −1 and MBC's in the range of 6.3-12.5 mg ml −1. Conclusions: : The presence of antibacterial activity in extracts of Elaeophorbia drupifera, Rauwolfia vomitoria and the leaves of Solanum verbascifolium, plants traditionally used to treat skin infections, are reported for the first time. Extracts from Alchornea cordifolia, also used to treat wounds, had the widest spectrum of antibacterial activity.

Research paper thumbnail of Non-specific cell mediated immunity in patients infected with Schistosoma mansoni in Kenya

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1982

Parameters of in vitro cell-mediated immunity (CMI) have been measured in the local Kenyan oooula... more Parameters of in vitro cell-mediated immunity (CMI) have been measured in the local Kenyan oooulation infected with Schistosoma mansoni. Lvmphbcyte responses to the non-specific T cell mitogens Concanavalin A (Con A) and Phytohaemagglutinin (PHA) were reduced in about 60% of schistosomiasis patieits. Lymphocytes from control uninfected, and S. mansoni-infected donors formed equal numbers of spontaneous rosettes with sheep red blood cells, indicating that there was no overall reduction in the percentage numbers of T cells in the schistosomiasis patients.

Research paper thumbnail of Birds on Lake Shala islands, 6 August 1988

Research paper thumbnail of The Effects of Pregnancy on the Immunological Competence of Congenitally Athymic (Nude) Mice

Research paper thumbnail of The effect of cicerfuran, related arylbenzofuransand stilbenes on Leishmania aethiopica, L. tropica, and L. major promastigotes

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2003

insecticide-treated nets (ITN) are a key strategy for malaria control in Ghana. However, little i... more insecticide-treated nets (ITN) are a key strategy for malaria control in Ghana. However, little is known about the species composition and insecticide susceptibility of vector populations. This paper presents an initial survey of the distribution of molecular forms of Anopheles gambiae and insecticide resistance (the kdr mutation) from 579 mosquitoes collected from 8 sites in 2 ecological zones in southern Ghana. The molecular Plasma vitamin A and E levels of HIV-infected and HIV-uninfected Zambian women during pregnancy and lactation

Research paper thumbnail of The Effect of Cicerfuran, an Arylbenzofuran fromCicer bijugum, and Related Benzofurans and Stilbenes onLeishmania aethiopica,L.tropicaandL.major

Research paper thumbnail of Genetic and Immunological Aspects of Litter Size in the Mouse

European Journal of Immunogenetics, 1976

The effects of antigenic differences between mother and fetus on implantation number and on post-... more The effects of antigenic differences between mother and fetus on implantation number and on post-implantation mortality were studied. No evidence was found to support the hypothesis that these two measurements were affected by such antigenic differences or by prior immunization of the mother to paternal antigens. I N T R O D U C T I O N Litter size at birth is a complex characteristic, and is dependent on four major factors each of which determines the upper numerical limits of the next: (1) The number of ova shed. (2) The number of ova fertilized. (3) The number of blastocysts that successfully implant. (4) The number of implanted blastocysts which develop to term.

Research paper thumbnail of The Effect of Pregnancy on Lymph Node Weight in the Mouse

International Journal of Immunogenetics, 1977

SUMMARYLumbar and renal lymph nodes, inguinal lymph nodes and spleen weights were recorded during... more SUMMARYLumbar and renal lymph nodes, inguinal lymph nodes and spleen weights were recorded during pregnancy in mice after mating with males of the same (syngeneic) or a different (allogeneic) strain. The weights of these nodes increased during pregnancy. Spleen weights increased up to the fifteenth day of pregnancy and then decreased in weight. There was no consistent correlation of any of these measurements with the extent of the antigenic dissimilarity between mother and conceptus.

Research paper thumbnail of Leishmanicidal Activity of Yucatecan Medicinal Plants on Leishmania Species Responsible for Cutaneous Leishmaniasis

Journal of Parasitology, 2009

Research paper thumbnail of Interaction between Leishmania parasites and mammalian macrophages

Research paper thumbnail of An immunosuppressive factor in the serum of patients with schistosomiasis

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1980

Research paper thumbnail of Demonstration of mycobacterial antigens in nerve biopsies from leprosy patients using peroxidase-antiperoxidase immunoenzyme technique

Clinical immunology and …, 1983

Peripheral nerve biopsies from patients with leprosy were stained with anti-Mycobacterium bovis (... more Peripheral nerve biopsies from patients with leprosy were stained with anti-Mycobacterium bovis (BCG) in a peroxidase-antiperoxidase (PAP) system to demonstrate intraneural mycobacterial antigens. Most M. leprae antigens have been shown to crossreact with BCG ...

Research paper thumbnail of The Influence of Parity and Maternal Preimmunization on Fetal Survival in Mice

Reproduction, 1974

A common immunological consequence of pregnancy is that the mother may become sensitized to fetal... more A common immunological consequence of pregnancy is that the mother may become sensitized to fetal or paternal antigens (Goodlin & Herzenberg, 1964; Kaliss & Dagg, 1964; Soren, 1967). Recently, Maroni & Parrott (1973) have demonstrated that cell-mediated immunity against paternal antigens increases with parity. We have attempted to compare the results of normal parity with artificial immunization designed to simulate maternal sensitization to paternal antigens.

Research paper thumbnail of Fetal Wastage as a Consequence of Mycoplasma Pulmonis Infection in Mice

Reproduction, 1975

The effect of Mycoplasma pulmonis, strain JB, on the outcome of pregnancy in TO mice was studied.... more The effect of Mycoplasma pulmonis, strain JB, on the outcome of pregnancy in TO mice was studied. The mice were infected intravenously before or after mating and the fetuses were examined at autopsy just before parturition. An increase in the number of abnormal pregnancies was noted in mice infected about 2 weeks before mating, and there was a significant increase in the number of fetuses which died midway through pregnancy. Mycoplasmas were not isolated from any of the fetuses although the organisms reached the joints of the pregnant mice and caused arthritis. It is possible, therefore, that maternal upset was a factor in these abnormal pregnancies. In mice infected at various times after mating, abnormal pregnancies were most frequently seen in those infected 9 days after mating. There was an increase in the number of both mid-and late-stage fetal deaths in these mice and also an increase in the number of late-stage fetal deaths in mice infected 5 days after mating. Mycoplasmas were isolated not only from most ofthe dead fetuses but also from living ones which suggests that in most instances death was probably due to maternal infection and disturbance rather than fetal infection per se. The possibility of modifying this mouse model by establishing a chronic genital tract infection is discussed as a means of investigating the r\l=o^\leof mycoplasmas in human abortion.

Research paper thumbnail of The Effects of Active Immunization on the Decidual Cell Reaction and Ectopic Blastocyst Development in Mice

Reproduction, 1975

One of the most striking features of early pregnancy in the mouse is the development of the decid... more One of the most striking features of early pregnancy in the mouse is the development of the decidual cell reaction (DCR). This cellular proliferation

Research paper thumbnail of Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites?

Parasitology, 2008

SUMMARYLeishmania parasites invade host macrophages, causing infections that are either limited t... more SUMMARYLeishmania parasites invade host macrophages, causing infections that are either limited to skin or spread to internal organs. In this study, 3 species causing cutaneous leishmaniasis, L. major, L. aethiopica and L. tropica, were tested for their ability to interfere with apoptosis in host macrophages in 2 different lines of human monocyte-derived macrophages (cell lines THP-1 and U937) and the results confirmed in peripheral blood mononuclear cells (PBMC). All 3 species induced early apoptosis 48 h after infection (expression of phosphatidyl serine on the outer membrane). There were significant increases in the percentage of apoptotic cells both for U937 and PBMC following infection with each of the 3 species. Early apoptotic events were confirmed by mitochondrial membrane permeabilization detection and caspase activation 48 and 72 h after infection. Moreover, the percentage of infected THP-1 and U937 macrophages increased significantly (up to 100%) following treatment with ...

Research paper thumbnail of Leishmania aethiopica: Infections in laboratory animals

Experimental Parasitology, 1989

Leishmania aethiopica parasites were inoculated into 11 different strains and species of small la... more Leishmania aethiopica parasites were inoculated into 11 different strains and species of small laboratory animals. Clinical lesions were only produced following inoculation of hamster noses and thus this parasite is highly selective in both species and site for the laboratory animals tested. Parasites could, however, be recovered from draining lymph nodes 3 weeks after infection of BALB/c mice. Lesions in hamsters were progressive and nonulcerating (up to 1 year) and histologically resembled diffuse cutaneous leishmaniasis (DTH) in man. Pronounced delayed hypersensitivity responses to L. aethiopica antigens only developed in mice despite the absence of clinical lesions. Weak DTH responses were produced in hamsters with clinical lesions only after 25 weeks of infection.

Research paper thumbnail of Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites

Research paper thumbnail of Cutaneous leishmaniasis in south-western Ethiopia: Ocholo revisited* 1

Transactions of the …, 1992

The borough of Ocholo, on the western side of the Ethiopian Rift Valley, is an endemic focus for ... more The borough of Ocholo, on the western side of the Ethiopian Rift Valley, is an endemic focus for Leishmania aethiopica infection and has been surveyed thrice between 1987 and 1990. In 1989,3022 inhabitants (>95% of the population) were interviewed and examined. The overall prevalence of localized cutaneous leishmaniasis (LCL) was 36-+0%, with a peak value of 8.5% in the O-10 years old age group. In half of the patients the active disease was estimated to last for 9.6*6 months; in lo%, it exceeded 3 years. Scars of LCL were present in 34.3% of the residents. Leishmanin skin tests were positive in 54% of 120 school-children without signs of the disease. Therefore, in Ocholo a minimum of 71.6% of the population has been exposed to L. aethiopica infection. Two cases of the diffuse form of cutaneous leishmaniasis were observed. In this highland biotope, Phlebotomus pedifer was found to be the major, and possibly the only, vector for L. aethiopica.