Biomedical subjects

M Spencer

Publications and source records attributed to M Spencer.

At least 19 recordsLinked to original sources

PubMed1992

The history of malaria control in the southwest Pacific region, with particular reference to Papua New Guinea and the Solomon Islands.

A number of phases in the history of malaria control in the Southwest Pacific Region can be recognized. During the first phase (1898-1923) it was known that anopheline mosquitoes carried malaria, but as yet the identity of the local vectors had not been established. The incrimination of the vectors in 1923 gave a sound basis for control, which remained largely urban in location except for the distribution of the larvivorous fish Gambusia affinis. The exigencies of the Pacific War and the presence of large numbers of combat troops in malarious areas resulted in the establishment of Mobile Entomological Sections and Malaria Control Units, and the collection and collation of large amounts of entomological, epidemiological and parasitological information. Larval control measures, carried out with very large labour lines and with military precision, were effective. The availability of dichlorodiphenyltrichloroethane (DDT) in 1943 made attack on adult vector mosquitoes also possible; DDT was applied widely in Papua New Guinea and the Solomon Islands by spraying and misting with adulticidal devices in tents and buildings, and by release from aircraft. Atebrin and dimethylphthalate also became available in quantity, for the suppression and treatment of malaria and for personal protection against mosquitoes, respectively. The wartime successes gave hope for peacetime anti-malaria activities carried out within village communities, which to this stage had not been seriously attempted. By three years after the end of the war the World Health Organization, the South Pacific Commission, and local administrative structures had been set up. Extensive investigations into the nature and severity of malaria endemicity were undertaken and recorded. Initially malaria control remained localized and largely urban, and was carried out by conventional antilarval measures, but at the same time new anti-malaria compounds became available for prophylaxis and treatment. Uncertainty still remained as to the usefulness of indoor spraying with DDT against anophelines of the punctulatus group. By 1953 the results of detailed studies in test huts set up for the purpose were known to been couraging, and the decision was made in 1954 to begin in Netherlands New Guinea (West Irian) a pilot project of routine residual spraying with DDT in village houses.(ABSTRACT TRUNCATED AT 400 WORDS)

History, 19th Century↗

PubMed1991

Dose-dependent responses to nerve growth factor by adult rat cholinergic medial septum and neostriatum neurons.

This study describes the relationship between the concentration of intraventricularly infused nerve growth factor (NGF) and several responses by axotomized cholinergic medial septum neurons and normal cholinergic neostriatal neurons of the adult rat. NGF infused for 14 days starting either immediately after a unilateral fimbria-fornix transection or after a 2-week delay period elicited similar dose-response relationships for the maintenance or restoration of ChAT and NGF receptor positivity and cell body size and for intraseptal 'sprouting' of the axotomized medial septum neurons. Thus, in the medial septum it appears that the expression of 'marker' molecules, cell body size and the induction of 'sprouting' are regulated by virtually the same concentrations of NGF in the two treatment strategies. This suggests that NGF has a general regulatory role and injured but untreated neurons remain fully susceptible to NGF at least up to 2 weeks after the lesion. A 14-day infusion with NGF also induced an above-normal cell body size (hypertrophy) both in axotomized medial septum and in intact striatal cholinergic neurons. The hypertrophic response of normal striatal neurons required less NGF than did that of medial septum neurons. Since the striatal response began to be detectable at a similar concentration as that required for the full maintenance or restoration of ChAT and NGF receptor positivity it could be seen as an unwanted side-effect. The definition of a sub-optimal dose with which a significant, but not maximal response can be elicited will allow future evaluations of potentially additive or synergistic actions by other agents.

Animals↗

PubMed1991

Recoverin: a calcium sensitive activator of retinal rod guanylate cyclase.

Vertebrate retinal photoreceptors recover from photoexcitation-induced hydrolysis of guanosine 3', 5'-monophosphate (cyclic GMP) by resynthesizing cyclic GMP, which reopens cation channels that have been closed by light. Activation of guanylate cyclase by light-induced depletion of cytosolic calcium is a key event in this recovery process. This cyclase has now been shown to be regulated by a 23-kilodalton calcium binding protein. The protein is present in both rod and cone photoreceptors and was named recoverin because it promotes recovery of the dark state. The amino acid sequence of recoverin exhibits three potential calcium binding sites (EF hands). That recoverin binds calcium was confirmed with calcium-45 and by observing calcium-induced changes in its tryptophan fluorescence. Recoverin activated guanylate cyclase when free calcium was lowered from 450 to 40 nM, an effect that was blocked by an antibody to recoverin. Thus, guanylate cyclase in retinal rods is stimulated during recovery by the calcium-free form of recoverin. A comparison of recoverin with other calcium binding proteins reveals that it may represent, along with the protein visinin, a family of proteins that are regulated by submicromolar calcium concentrations.

Amino Acid Sequence↗

PubMed1991

Peripheral visual changes and spatial attention.

Three experiments are reported investigating the attentional effects of peripheral visual changes. In agreement with previous work, experiment 1 demonstrated facilitatory and inhibitory effects of a peripheral visual change on the latency of peripheral target detection. However, after a few minutes practice the facilitatory effect disappeared entirely. The inhibitory effect, though slightly reduced in later blocks, remained significant. Hence, the two effects are dissociable and not inter-dependent as argued by Maylor (1985). In experiments 2 and 3 the perceptual salience of the peripheral cue was manipulated. With a low energy, barely noticeable cue there was no reduction in either facilitation or inhibition as a function of practice. In contrast, the attentional effects of cues higher in energy tended to diminish with practice. Theoretical implications of these data are discussed.

Adult↗

PubMed1991

The 1.97 cent solution: low tech capsulorhexis and hydrodissection.

Capsulorhexis is becoming the favored technique for performing anterior capsulectomy. This report describes a simple method for performing capsulorhexis and nuclear hydrodissection without the use of viscoelastics or specialized instruments.

Cataract Extraction↗

PubMed1991

A randomised placebo-controlled trial of topical cysteamine therapy in patients with nephropathic cystinosis.

Five patients with nephropathic cystinosis were evaluated to assess the ability of topical cysteamine to clear corneal cystine crystals. All patients were randomised to receive topical cysteamine 0.2% six times a day in one eye with normal saline in the other eye as a control. All five patients showed some improvement in visual symptoms (photophobia, blepharospasm and visual acuity) together with an improvement in corneal crystal density. Three of these also had an improvement in Snellen visual acuity and contrast sensitivity.

Adolescent↗

PubMed1979