Onchocerca fasciata: histochemical demonstration of succinate and NADH dehydrogenase

The activities of selected enzymes of the respiratory chain system in Onchocerca fasciata (Filarioidea: Onchocercidae) have been investigated histochemically. Thus, the localization and distributions of NADH dehydrogenase (EC 1.6.99.3), succinate dehydrogenase (SDH) (EC 1.3.99.1) and cytochrome oxidase (EC 1.9.3.1) were investigated in various tissues of the adult female worm by employing MTT, Nitro BT (dehydrogenases) and DAB (cytochrome oxidase). Different tissues varied considerably in their enzymatic activities. The hypodermis and reproductive tissues showed strong and identical localization of NADH and SDH dehydrogenase activities reflecting high metabolic rates. Little or no dehydrogenase activities were observed in the intestine and cuticle. In contrast to the two dehyrogenases, no activity was observed for cytochrome oxidase in any of the tissues in adult or embryonic stages of the worm. The significance of these results with respect to the energy metabolism of the worm is discussed. It is suggested that O. fasciata lacks a classical, mammalian-type respiratory pathway and that oxidative phosphorylation is of no importance as an energy generating pathway in this essentially anaerobic parasite.

Onchocerca fasciata: enzyme histochemistry and tissue distribution of various dehydrogenases in the adult female worm

Histochemistry studies of key dehydrogenases in the glycolytic pathway and related enzymes and the tricarboxylic acid (TCA)-cycle enzymes were carried out on adult female Onchocerca fasciata. The distribution pattern and enzymatic activities of 6-phosphogluconate dehydrogenase (6-GPDH), lactate dehydrogenase (LDH), mitochondrial glycerol-3-phosphate dehydrogenase (GPDH), nicotinamide adenine dinucleotide (phosphate) [NAD+(P)]-linked isocitrate dehydrogenase (ICDH), and NAD+(P)-linked malate dehydrogenase (MDH) in various tissues of the worm were determined. Moderate to intense enzyme activities were localized in three main areas, namely, the hypodermis, body-wall muscle, and reproductive tissues. Activity of the formazan reaction product was very low, if at all present, in the intestinal epithelium and was completely absent in the cuticle. On the basis of the present results and earlier observations, it is suggested that glycolysis leading to the end product lactate is the main energy-generating pathway in O. fasciata. The presence of significant activity of 6-GPDH indicates that the pentose-phosphate pathway might be operative in O. fasciata. In light of the activity of some of the TCA-cycle enzymes, ICDH and MDH, demonstrable in O. fasciata, it is possible that an additional pathway (pyruvate-succinate) of glucose metabolism via a reverse sequence of the TCA cycle may also be operative in the worm. The possible functional significance of the enzymes detected is discussed with respect to their location.

Deleterious effects of khat addiction on semen parameters and sperm ultrastructure

The semen parameters and sperm ultrastructural morphology have been described in semen samples from two groups of Yemeni subjects. The first 'exposed' group comprised 65 khat addicts, while the second control group included 50 non-khat addict subjects. The mean age was 39.94 +/- 13.85 and 35.72 +/- 11.35 years in the exposed and control groups respectively, without a significant difference. The mean duration of khat addiction among the addicts was 25.34 +/- 12.96 years (range 6.00-48.00). Statistically significant differences were detected between the semen parameters of the two groups. Such parameters, including semen volume, sperm count, sperm motility, motility index and percentage of normal spermatozoa, were lower among addicts. Significant negative correlation was also found between the duration of khat consumption and all semen parameters (r ranged from -0.30 to -0.74). At the transmission electron microscopy level, a counting system was incorporated to compare the numbers of normal spermatozoa with deformed and dead spermatozoa in ultrathin plastic sections. The total mean percentage of deformed spermatozoa was approximately 65%. Different patterns of sperm deformation were demonstrated, and included both the head and flagella in complete spermatozoa, aflagellate heads, headless flagella and multiple heads and flagella. Deformed heads showed aberrated nuclei with immature nuclear chromatin and polymorphic intranuclear inclusions; these were associated with acrosomal defects. The deformed flagella demonstrated numeric aberrations of the axonemal 9 + 2 configuration and structural defects of their associated elements. Persistent cytoplasmic droplets were observed frequently. This study has shown for the first time the deleterious effects of khat addiction on semen parameters in general and sperm morphology in particular of all addicts, especially those who have consumed khat for longer periods of time.

Histochemical localization of key glycolytic and related enzymes in adult Onchocerca fasciata

The activities of some key enzymes of the glycolytic and pentose phosphate pathways were investigated histochemically in adult female Onchocerca fasciata (Nematoda: Filarioidea). The distribution patterns of phosphofructokinase (PFK), aldolase (ALD), glyceraldehyde 3-phosphate dehydrogenase (G3PDH) and glucose 6-phosphate dehydrogenase (G6PDH) in different tissues of the worm were determined by employing NitroBlue Tetrazolium (NBT). The glycolytic enzymes PFK, ALD, and G3PDH were distributed throughout the hypodermal tissue, somatic muscles and reproductive organs. These enzyme activities were predominantly expressed in the hypodermal and reproductive tissues, both of which appeared to be metabolically more active than adjacent tissues. The high activities of the enzymes studied in the hypodermal tissue when compared with the minimal or low activity in the intestinal epithelium support the assumption that the worm's intestine, in contrast to the body wall, plays no significant role in the nutrient acquisition process. The results emphasize that both the glycolytic and hexose monophosphate pathways of carbohydrate metabolism are active components in energy production and biosynthetic processes in the various tissues of the worm. The functional significance of these glucose-metabolizing enzymes has been discussed with regard to their location in the tissues concerned.

Histochemical distribution of hydrolytic enzymes in adult Onchocerca fasciata (Filarioidea: Onchocercidae)

Histochemical techniques were employed to study the tissue distribution of hydrolytic enzymes in adult female Onchocerca fasciata (Filarioidea: Onchocercidae). Different tissues differed considerably in the localization and distribution of the six enzymes studied. Acid phosphatase (AcPase) activity was detected in the cuticle, hypodermis and reproductive organs. Alkaline phosphatase (AlkPase) activity was largely absent. Adenosine triphosphatase (ATPase) was found in the somatic musculature and muscles of the uterine ducts, whereas 5'-nucleotidase (5'-Nu) was restricted to young oocytes and dividing embryos in the female worm. Strong glucose-6-phosphatase (G-6-Pase) activity was demonstrated in the uterine epithelial cells and microfilariae, as was weak activity in the hypodermis. Naphthylamidase (NAM) activity was detected in the hypodermis, with lower activity occurring in the somatic musculature. The possible functions of these enzymes are discussed with respect to their location. The hydrolytic enzymes AcPase and NAM in the body wall are probably involved in absorptive-digestive functions, NAM in the somatic musculature may be concerned with tissue protein turnover, and ATPase, 5'-Nu and G-6-Pase may have a role in active transport and energy metabolism.

Histochemical distribution of esterases in adult Onchocerca fasciata (Filarioidea: Onchocercidae)

The localization and distribution patterns of non-specific esterases (NSE) and acetylcholinesterase (AChE) activities in adult female Onchocerca fasciata (Filarioidea: Onchocercidae) have been determined using enzyme histochemical techniques. NSE activity was highest in the hypodermis and mild to moderate in the somatic musculature and uterine epithelium. The intensity of the reaction was decreased but not eliminated by sodium fluoride. AChE activity was found in the hypodermis and cuticle of the female worm, highest in fully formed microfilariae in the uterus, whereas early oocytes and embryonic forms were negative. Butyrylcholinesterase activity showed similar but less intense staining reactions at the same sites. Eserine-treated sections showed no AChE activity in all areas where it is usually present. The present techniques failed to demonstrate AChE activity in the nervous tissue including the hypodermal nerve trunks and neuromuscular junctions of the worm. The possible functional significance of the demonstrable enzymes was discussed with respect to their location. NSE activity may be involved in lipid metabolism, whereas AChE activity may have a role in host-parasite relationship.