Volume 42, Issue 4
October 1955, pages 129-194
pp 129-144 October 1955
Eleven fields situated in the cotton growing tracts of Coimbatore and Tirunelveli districts in Southern India were investigated for the occurrence of Fusaria with reference to the variability in the pathogenic manifestation of the different species inhabiting these soil types.
F. chlamydosporum, F. culmorum, F. oxysporum andF. solani were the most commonly occurring species out of the fourteen species isolated from the soil.F. camptoceras, F. dimerum, F. sporotrichioides andF. tricinctum were recorded for the first time in Southern Indian soils, of theseF. sporotrichioides andF. tricinctum are new records for India.
F. avenaceum, F. camptoceras, F. chlamydosporum, F. dimerum, F. poae, F. scirpi, F. semitectum, F. sporotrichioides andF. tricinctum were non-pathogenic on cotton and pigeonpea, whilstF. culmorum, F. oxysporum andF. solani comprised pathogenic and non-pathogenic strains; a number of transitional forms were observed between the virulent and avirulent isolates pathogenic on cotton and pigeonpea, indicating that Fusaria occur in soils in a multiplicity of pathogenic forms. In certain strains of the highly specialized ‘wilt’ Fusaria,F. udum andF. vasinfectum, host selectivity was observed, whereas many other isolates were non-specific to the host. The significance of these results in the taxonomy of Fusaria is discussed.
Many of the isolates were capable of causing disease reaction in the host when present in soil either individually or in combination; mixing two isolates resulted either in synergism and augmentation in pathogenicity or in antagonism and decrease in infection.
pp 145-153 October 1955
The toxin ofF. vasinfectum, fusaric acid, has no host specificity despite the fact that there is specificity of hosts infected by this pathogen.
Resistant cotton plants (Gossypium hirsutum), in spite of being infected byF. vasinfectum do not manifest visual symptoms. A study of their metabolism clearly indicates that resistance is due to the higher reserve of carbohydrates and ascorbic acid over the susceptible plants. It is likely that these energy-yielding substances are favourably utilised in the resistant plants for the formation of a labile toxic substance which inhibits the pathogen inside the vascular system.
pp 154-161 October 1955
A comparative study of different lines of strain bda (Bar) with and without milk borne tumor agent was undertaken with special reference to (1) Maturation of ovaries; (2) Histology of adrenal glands; and (3) Mammary morphology. Qualitative difference in the maturation of ovaries, X-zone degeneration in adrenals and mammary morphology indicate the influence of milk borne agent on the hormonal metabolism. Although genetic constitution primarily determines the hormonal pattern, milk borne agent appears to exert secondary influence on the hormonal system in intact mice.
pp 162-171 October 1955
(a) (1) Three strains of mice C3H, C57 (B1) and Strong A have been ovariectomised within 36 hours of birth and adrenal and secondary sex organ response to gonadectomy has been studied at a late age of twelve to fourteen months.
An additional group of strain A breeders have been castrated after one pregnancy and similar studies have been carried out on “A” breeder castrates at old age.
(2) Cancer-susceptible strain C3H presented specific post castrational changes—such as advanced adrenal cortical hyperplasia associated with heavy vaginal keratinisation and extensive development of mammary ducts. Such response was conspicuously absent in the strain C57 (B1) and A virgin castrates as well as breeder castrates.
(b) (3) Using the experimental animals in (a) as controls, more litters of C3H and C57 (B1) were castrated and exchanged for foster-nursing. The effect of foster-nursing on the response of adrenals and secondary sex organs to gonadectomy was studied at old age.
(4) The adrenal response to gonadectomy has been proved to be primarily strain specific. However, there is an indication of the influence of ‘the milk borne agent’ on the adrenals and calcium metabolism in the resistant strain C57 (B1) foster-nursed on C3H milk.
pp 172-182 October 1955
1. The reaction of blood vessels to sodium and potassium ions have been studied: (a) by perfusing the hind limbs of the dog with isotonic solutions of sodium and potassium chlorides; (b) by direct microscopic observation of the blood vessels in the mesentery of the guinea pig and dog; (c) by studying the reaction of rings from dog’s aorta.
2. The effect of the above ions on the contractile mechanism of the smooth muscle of the arterioles was studied by the dying muscle technique and by prior heating to 50°C.
3. Sodium has a contractile and potassium, a relaxing effect on the contractile mechanism of the smooth muscle of the arterioles. This explains the role of sodium in essential hypertension.
pp 183-190 October 1955
1. The action of cholesterol on the excitatory and the contractile mechanisms of unstriated muscle has been described.
2. Cholesterol causes contraction of dog’s and frog’s stomach muscle by action on the excitatory system. It changes the nature of tone, so that the muscle is unable to relax.
3. Cholesterol increases the tone of the blood vessels of dog’s hind limbs.
4. Cholesterol causes contraction of the contractile mechanism of unstriated muscle; this contraction is dependent upon the ionic balance.
5. It is concluded that cholesterol may be active in later stages of hypertension, in increasing tonus of arterioles, and producing irreversibility.
pp 191-194 October 1955
1. The action of calcium on the contractile mechanism of the unstriated muscle of the arterioles has been studied by prolonged immersion of dog’s hind limbs in solutions of calcium chloride and recording the rate of flow before and after immersion for 24 hours.
2. Isotonic solutions of calcium chloride produce a strong irreversible contraction of the arterioles. This is due to the action of calcium on the contractile mechanism.
3. The possible role of calcium in hypertension has been discussed.