Conversion of beta sitosterol to cholesterol blocked in an insect by hypocholesterolemic agents

Two vertebrate hypocholesterolemic agents (triparanol and 22,25-diazacholesterol) block the conversion of beta-sitosterol to cholesterol in the larva of the tobacco hornworm, Manduca sexta (Johannson). A primary site of inhibitory action is the terminal step in this conversion-the reduction of desmosterol (24-dehydrocholesterol) to cholesterol. This is also the site at which these compounds inhibit de novo cholesterol biosynthesis in higher animals. Both agents severely inhibit growth and maturation of the tobacco hornworm.     

In vitro cultivation of Ostertagia ostertagi, the medium stomach worm of cattle. II. Effect of insect-growth-disrupting amines and amides on development

Thirteen secondary and tertiary amides and amines that disrupt growth and development in certain insects were tested at concentrations of 0.25–5.0 p.p.m. for their effects on development of Ostertagia ostertagi, from infective larvae to egg-laying adults, in a two-step roller culture system. These compounds did not affect exsheathment of infective larvae. However, some of these compounds inhibited development or killed 100% of the exsheathed larvae at concentrations of 1.0–2.5 p.p.m. Minimum inhibitive concentrations of several of the amines and amides affected the nematodes in one or more of the following ways: decreased motility or paralysis; reduced survival; delayed or blocked third or fourth ecdysis; lowered yields of advanced stages; decreased production of fertile and non-fertile eggs. The results also indicated that, as in insects, these chemicals exerted their lethal effects against O. ostertagi at the time of molt.     

Namoratunga: the first archeoastronomical evidence in sub-saharan Africa

Namoratunga, a megalithic site in northwestern Kenya, has an alignment of 19 basalt pillars that are nonrandomly oriented toward certain stars and constellations. The same stars and constellations are used by modern eastern Cushitic peoples to calculate an accurate calendar. The fact that Namoratunga dates to about 300 B.C. suggests that a prehistoric calendar based on detailed astronomical knowledge was in use in eastern Africa.     

Ecdysone analog: conversion to alpha ecdysone and 20-hydroxyecdysone by an insect

The tritium-labeled synthetic ecdysone analog Delta(7)-5beta-cholestene-2beta,-3beta,14alpha-triol-6-one terminated diapause when injected into diapausing tobacco hornworm pupae and was converted into tritium-labeled alpha-ecdysone and tritium-labeled 20-hydroxyecdysone. About half of the crystalline alpha-ecdysone and 20-hydroxyecdysone isolated from the tobacco hornworms 7(1/2) to 8(1/2) days after injection was derived from endogenous steroid precursors and half from the transformation of the synthetic ecdysone analog.     

Crystal structure of Cd,Zn metallothionein

The anomalous scattering data from five Cd in the native protein were used to determine the crystal structure of cadmium, zinc (Cd,Zn) metallothionein isoform II from rat liver. The structure of a 4-Cd cluster was solved by direct methods. A 2.3 A resolution electron density map was calculated by iterative single-wavelength anomalous scattering. The structure is folded into two domains. The amino terminal domain (beta) of residues 1 to 29 enfolds a three-metal cluster of one Cd and two Zn atoms coordinated by six terminal cysteine thiolate ligands and three bridging cysteine thiolates. The carboxyl terminal domain (alpha) of residues 30 to 61 enfolds a 4-Cd cluster coordinated by six terminal and five bridging cysteine thiolates. All seven metal sites have tetrahedral coordination geometry. The domains are roughly spherical, and the diameter is 15 to 20 A; there is limited contact between domains. The folding of alpha and beta is topologically similar but with opposite chirality. Redundant, short cysteine-containing sequences have similar roles in cluster formation in both alpha and beta.