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Biomedical subjects

J B Walker

Publications and source records attributed to J B Walker.

At least 55 records · Page 3Linked to original sources
PubMed1984

Records of the bont tick, Amblyomma hebraeum, from the angulate tortoise, Chersina angulata, and the leopard tortoise, Geochelone pardalis.

A. hebraeum nymphae were found on 4 angulate tortoises and 13 leopard tortoises in the Addo Elephant National Park, Eastern Cape Province. Adults of this species were collected for the 1st time from a leopard tortoise in the Mkuze Game Reserve, Natal. The significance of this finding, in relation to the normal host preferences of this tick, is briefly discussed.

Animals↗
PubMed1983

Synthesis and accumulation of an extremely stable high-energy phosphate compound by muscle, heart, and brain of animals fed the creatine analog, 1-carboxyethyl-2-iminoimidazolidine (homocyclocreatine).

A new creatine analog, 1-carboxyethyl-2-iminoimidazolidine (homocyclocreatine), has been synthesized and compared with other synthetic analogs of creatine as a substrate for creatine kinase under both in vitro and in vivo conditions. Reactivity with rabbit muscle creatine kinase at 2 mM and pH 7.0 occurred in the order: creatine greater than cyclocreatine (1-carboxymethyl-2-iminoimidazolidine) greater than N-ethylguanidinoacetate greater than N-propylguanidinoacetate greater than guanidinoacetate greater than N-methyl-3-guanidinopropionate greater than 3-guanidinopropionate greater than homocyclocreatine. Homocyclocreatine was 10,000-fold less active than creatine. In the reverse direction at 0.2 mM and pH 7.0: creatine-P greater than N-ethylguanidinoacetate-P greater than cyclocreatine-P much greater than homocyclocreatine-P. Homocyclocreatine-P was 200,000-fold less active than creatine-P. The phosphoryl group transfer potential of homocyclocreatine-P was estimated to be 2 kcal/mol lower than that of creatine-P. Chicks fed 5% homocyclocreatine for 16 days synthesized and accumulated homocyclocreatine-P in breast muscle (32 mumol/g wet wt), leg muscle (24 mumol/g), heart (7 mumol/g), intestine (8.5 mumol/g), and brain (2.4 mumol/g). During ischemia homocyclocreatine-P was utilized by muscle much more slowly for the regeneration of ATP than was creatine-P or cyclocreatine-P. Our results suggest that in tissues of homocyclocreatine-fed animals subjected to a sudden large increase in work load or to ischemia, the residual creatine-P system would rapidly equilibrate with the adenylate system at the new lower cytosolic phosphorylation potential, whereas in the same cytosol the (homocyclocreatine-P)/(homocyclocreatine) ratio would exhibit a hysteresis or memory effect and reflect for a considerable period of time the earlier higher (ATP)/(free ADP) ratio rather than the actual lower (ATP)/(free ADP) ratio.

Animals↗
PubMed1983

The ixodid tick burdens of various large ruminant species in South African nature reserves.

The ixodid tick burdens of eland (Taurotragus oryx), greater kudu (Tragelaphus strepsiceros), nyala (Tragelaphus angasi), bushbuck (Tragelaphus scriptus) and giraffe (Giraffa camelopardalis) in the Kruger National Park, Transvaal; of African buffalo (Syncerus caffer) and nyala in the Hluhluwe Game Reserve, Natal; and of gemsbok (Oryx gazella) in the Mountain Zebra National Park, an eland in the Thomas Baines Nature Reserve and an eland and greater kudu in the Andries Vosloo Kudu Reserve, eastern Cape Province, were determined. The tick burdens of animals shot at the same time and locality are compared, and the attachment sites of some tick species on some of the hosts are given.

Animals↗
PubMed1983

Clarification of the status of Rhipicephalus kochi Dönitz, 1905 (Ixodoidea, Ixodidae).

Figures of the types of Rhipicephalus kochi, and of its synonym Rhipicephalus neavei Warburton, 1912, are presented. These are accompanied by complete descriptions of all stages of R. kochi, illustrated with scanning electron microscope photographs. The basic differences between this species, Rhipicephalus pravus Dönitz, 1910 and Rhipicephalus punctatus Warburton, 1912 are outlined. R. kochi occurs south of the Equator in parts of eastern, central and southern Africa. Its adults feed most commonly on cattle, various antelopes and wild pigs, and on hares. Little is known about the hosts of the immature stages; nymphae have been recorded in a field collection once only, from Petrodromus tetradactylus, the 4-toed elephant shrew.

Africa, Southern↗
PubMed1982

Modulation of spasticity: prolonged suppression of a spinal reflex by electrical stimulation.

Electrical subcutaneous nerve stimulation of radial, median, and saphenous nerves has been shown to produce prolonged analgesia. In a double blind study, such stimulation also suppressed clonus for 3 hours after stimulation ceased in subjects with spasticity. Since the effect is contralateral, each subject was his own control. Because stimulation of the nerve in the wrist suppressed ankle clonus, the mechanism mediating the effect must be centrifugal inhibition. These results suggest that subcutaneous nerve stimulation may also be a tool in the management of spasticity.

Electric Stimulation↗
PubMed1982

The ecology of Rhipicephalus zambeziensis and Rhipicephalus appendiculatus (Acarina, Ixodidae) with particular reference to Zimbabwe.

R. zambeziensis, like R. appendiculatus, is primarily a parasite of domestic and wild herbivores, and sometimes carnivores. Both species occur in parts of east, central and southern Africa, but they are not as a rule sympatric. In general, R. zambeziensis occurs in hotter, drier areas than does R. appendiculatus, especially along some of the great river valleys. In Zimbabwe, R. zambeziensis is largely restricted to the northern, northwestern and southern parts of the country, whereas R. appendiculatus is widely distributed in the eastern and southern areas.

Animals↗
PubMed1981

Non-opioid pathways suppress pain in humans.

Subcutaneous electrical stimulation (SCNS) of median, radial, and saphenous nerves produces prolonged analgesia. The effect of subcutaneous nerve stimulation (SCNS) is not mediated by opiate receptors. (1) There is no cross-tolerance with opiates, and SCNS suppresses pain in patients under chronic meperidine medication. (2) Patients unresponsive to morphine benefit from SCNS. (3) There is no development of tolerance to SCNS. (4) SCNS analgesia is not naloxone-reversible. (5) SCNS can be administered with oral analgesics, either opiate or non-opiate, increasing patient comfort. These observations suggest that non-endorphinergic pathways produce powerful analgesia.

Analgesia↗
PubMed1981

Rhipicephalus zambeziensis sp. Nov., a new tick from eastern and southern africa, together with a redescription of Rhipicephalus appendiculatus Neumann, 1901 (Acarina, Ixodidae).

All stages of Rhipicephalus zambeziensis sp. nov. are described from laboratory-reared specimens of a strain originating from cattle near West Nicholson, Gwanda District, Zimbabwe. The redescription of all stages of Rhipicephalus appendiculatus is based primarily on laboratory-reared specimens of a strain originating from a mountain reedbuck (Redunca fulvorufula), Loskop Dam Nature Reserve, Transvaal, Republic of South Africa. The differences between these 2 species are discussed briefly. Details of the life cycle of R. zambeziensis under laboratory conditions are given, and attempts to cros-breed this species with R. appendiculatus are described and discussed.

Animals↗