Age-related changes in the response of hepatic succinic dehydrogenase activity to thyroxine and thiourea in lizards

Intraperitoneal injection of thyroxine (T4; 1 microgram/g body weight on alternate days, seven doses) to male garden lizards of three different age groups caused a stimulation of hepatic succinic dehydrogenase activity, the degree of response being higher in the old (63%) than in middle-aged (39%) and young (31%). Percent inhibition of enzyme activity following thiourea treatment (0.05 mg/g body weight on alternate days, three doses) was higher in middle-aged lizards (24%) than in young (10%) and old (12%) ones.     

Lipid composition of sputum from patients with asthma and patients with cystic fibrosis

Lipids from the sputum of patients with asthma and with cystic flbrosis were isolated and characterized. In both cases, lipids constituted approximately 30% of the dry material. Phosphatidylcholine was the most abundant lipid. Significant amounts of phosphatidylethanolamine and phosphatidylglycerol were present. Hexosyl ceramides, sphingomyelin, phosphatidylinositol, lysophosphatidylcholine, and lysophosphatidylethanolamine were present as minor lipid components. Appreciable quantities of neutral lipids were present, of which triglycerides and cholesterol were the main constituents. Phosphatidylcholine, sphingomyelin, and phosphatidylglycerol were highly saturated. Large amounts of phosphatidylcholine containing mostly palmitic acid, particularly in the asthmatic sputum, suggests that this highly saturated phospholipid is synthesized in the upper airways for reasons other than its beneficial surface-active properties in the alveoli.     

Seasonal variation in photogonadal response of the tropical weaver bird

A marked seasonal variation in photogonadal response of the tropical weaver bird has been demonstrated by shifting the birds from normal day length to continuous light every month of the year. While the gonadostimulatory effect of the long photoperiod was immediate during progressive, peak, and regressive phases of the reproductive cycle, the response was delayed by 1 to 3 months during the quiescent and regressive phases, respectively. Although a progressive decline in photosensitivity ensues after the gonads have attained a peak, weaver finches, unlike other photoperiodic passerine forms, do not develop a typical photorefractoriness which is described as spontaneous gonadal collapse and absence of redevelopment under continued long photoperiod. This is evident from the following: (1) gonadal activity is sustained indefinitely in extended long days; (2) during the period of gonadal regression birds are still photosensitive; (3) the sexually quiescent gonads of the postreproductive period can eventually be stimulated by long days; (4) the delayed photoresponse at this time cannot be “broken” by a pretreatment with long dark periods.     

Multiple emulsions: an overview

Multiple emulsions are complex polydispersed systems where both oil in water and water in oil emulsion exists simultaneously which are stabilized by lipophillic and hydrophilic surfactants respectively. The ratio of these surfactants is important in achieving stable multiple emulsions. Among water-in-oil-in-water (w/o/w) and oil-in-water-in-oil (o/w/o) type multiple emulsions, the former has wider areas of application and hence are studied in great detail. Formulation, preparation techniques and in vitro characterization methods for multiple emulsions are reviewed. Various factors affecting the stability of multiple emulsions and the stabilization approaches with specific reference to w/o/w type multiple emulsions are discussed in detail. Favorable drug release mechanisms and/or rate along with in vivo fate of multiple emulsions make them a versatile carrier. It finds wide range of applications in controlled or sustained drug delivery, targeted delivery, taste masking, bioavailability enhancement, enzyme immobilization, etc. Multiple emulsions have also been employed as intermediate step in the microencapsulation process and are the systems of increasing interest for the oral delivery of hydrophilic drugs, which are unstable in gastrointestinal tract like proteins and peptides. With the advancement in techniques for preparation, stabilization and rheological characterization of multiple emulsions, it will be able to provide a novel carrier system for drugs, cosmetics and pharmaceutical agents. In this review, emphasis is laid down on formulation, stabilization techniques and potential applications of multiple emulsion system.