Effects of starvation and sucrose feeding on corpora allata of last instar larvae of Manduca sexta: in vitro activity, size, and cell number

Abstract Larvae of the tobacco hornworm moth Manduca sexta starved for the first 3 days of the last (fifth) stadium undergo a supernumerary moult. If they are provided with sucrose during the starvation period, they develop into normal pupae although pupation is delayed. The activities of the corpora allata (CA) from normal, starved, and sucrose fed larvae were followed through the fifth stadium with a radiochemical assay for Juvenile Hormone (JH) biosynthesis. An attempt was made to correlate CA-activity with CA cell number, size, and protein content.
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated.     

HEDONIC SPREADABILITY OPTIMA OF SELECTED EDIBLE FATS

A panel of untrained judges was asked to assess spreadability of selected solid edible fat samples (butter, margarine, low fat products) of different temperature with regard to hedonic preferences. Instrumental measurements were performed by cone penetration with constant load. The statistical analysis of the ranked sensory data showed significant spreadability optima in the apparent yield value range of approximately 30–60 kPa. Differences between the selected fats were not observed.     

The main immunogenic region (MIR) of the nicotinic acetylcholine receptor and the anti-MIR antibodies

Myasthenia gravis (MG) is caused by autoantibodies against the nicotinic acetylcholine receptor (AChR) of the neuromuscular junction. The anti-AChR antibodies are heterogeneous. However, a small region on the extracellular part of the AChR alpha subunit, called the main immunogenic region (MIR), seems to be the major target of the anti-AChR antibodies, but not of the specific T-cells, in experimental animals and possibly in MG patients. The major loop of the overlapping epitopes for all testable anti-MIR monoclonal antibodies (MAbs) was localized within residues 67-76 (WNPADYGGIK for Torpedo and WNPDDYGGVK for human AChR) of the alpha subunit. The N-terminal half of alpha 67-76 is the most critical, Asn68 and Asp71 being indispensable for binding. Yet anti-MIR antibodies are functionally and structurally quite heterogeneous. Anti-MIR MAbs do not affect channel gating, but they are very potent in mediating acceleration of AChR degradation (antigenic modulation) in cell cultures and in transferring experimental MG in animals. Fab fragments of anti-MIR MAbs bound to the AChR prevent the majority of the MG patients' antibodies from binding to and causing loss of the AChR. Whether this inhibition means that most MG antibodies bind on the same small region or is a result of broad steric/allosteric effects is under current investigation.     

A preliminary report on a bacteriological assay for compound 1080 (sodium monofluoroacetate)

A new, inexpensive, simple and rapid bioassay for sodium monofluoroacetate (compound 1080) was developed using bacteria. Two 1080-sensitive isolates ( Bacillus sp. DHW and Acinetobacter sp. DHW) from local aquatic environments were tested on different agar media using the disc diffusion technique. Both bacteria exhibited zones of growth inhibition surrounding the 1080 discs that were linearly proportional to the concentrations (log₁₀) of 1080. Preliminary studies indicate that this technique can be used for assaying 1080 in environmental and biological samples.     

Root growth inhibition of the holorganic layer of moder humus under spruce (Picae abies KARST.) and beech (Fagus Silvatica L.)

A test of root growth inhibition of spruce and beech roots, according to Lynch's procedure (1977), shows the inhibitory effects of soil solution extracted from the holorganic layers (Of₂-Oh) under beech and spruce. Molecular gel filtration of soil solutions shows that the molecular weights vary over a wide range, from less than 100 to over 40,000 daltons. Chemical analysis, using CGC, HPLC and sometimes MS shows only negligible concentrations of simple aliphatic (C₁-C₅) and aromatic acids in the free state. Using the fraction scheme of Forsyth (1977) and the carbazole procedure, it is shown that uronic acids represent only a small percentage of the carboxylic acids, and have no inhibitory effects on root growth. By analogy with results of other authors, the presence of polycarboxylic acids in the soil solution are considered to be the main cause of root growth inhibition.     

Haplotype analysis of the human apolipoprotein B mutation associated with familial defective apolipoprotein B100.

Haplotype analysis was conducted on the mutant allele of 14 unrelated subjects heterozygous for a mutation in the codon for amino acid 3500 of human apolipoprotein B100. This mutation is associated with defective binding of low-density lipoprotein to the low-density lipoprotein receptor and with moderate hypercholesterolemia. Ten markers were used for haplotyping: eight diallelic markers within the structural gene and two hypervariable loci flanking the gene. Seven of eight unequivocally deduced haplotypes were identical, and one revealed only a minor difference at one of the hypervariable loci. The genotypes of the six other affected subjects were consistent with this same assigned haplotype. These data are consistent with a common ancestral chromosome and provide no evidence for a recurrent mutation at this potentially hypermutable CG dinucleotide, despite the fact that this mutation is not rare.