Maturation of locust corpora allata during the reproductive cycle: Effect of reserpine on allatotropic activity,juvenile hormone-III biosynthesis,and oocyte development

Reserpine, at doses of 20–175 μg per g body weight, severely retards oogenesis in newly emerged adult female migratory locusts (Locusta migratoria migratorioides) but does not increase mortality during the first 9 days and only slightly delays somatic growth. Total protein, and hemolymph vitellogenin content particularly, are significantly reduced in reserpine-treated locusts. The synthesis of juvenile hormone III (JH-III) following adult emergence, essential for induction of vitellogenesis and subsequent oogenesis, is dependent on the maturation and activation of the corpora allata (CA). CA of 7- to 8-day-old female locusts, treated with reserpine at day 1 after adult emergence, are only marginally active in vitro and are only slightly stimulated by an allatotropic factor. The basal activity and response of CA from the reserpine-treated locusts resembles that of newly emerged locusts, suggesting that reserpine specifically retards the initial maturation of the locust CA. Recovery of basal CA activity is evident on days 12–13 in reserpine-treated locusts, but responsiveness to the allatotropic factor is not recovered. Starvation of newly emerged females for 3 days and subsequent feeding did not effect ooctye development or CA activity. Cerebral content of the allatotropic factor, assayed on days 7–8, is not reduced by the reserpine treatment.     

Partial purification and characterization of locust allatotropin I

Methanol extracts of locust brains, corpora cardiaca (CC), and suboesophageal ganglia (SOG) were separated by gradient and/or isocratic reverse-phase high-performance liquid chromatography (HPLC) and allatotropic activity monitored in the eluted fractions. A major peak of activity, separated by isocratic separation with 12% 2-propanol, designated allatotropin I, exhibited identical retention times in the three tissue extracts. Doseresponse curves of allatotropin I indicate similar content in brain and CC-equivalents, whereas optic lobes, similarly separated by isocratic HPLC, contain only one-tenth of this amount of allatotropin. Allatotropin I is resistant to boiling and is susceptible to tryptic and chymotryptic digestion. Methanol extracts of thoracic muscle, Malpighian tubules, fat body or ovaries, similarly prepared and boiled, did not exhibit allatotropic activity at high doses of tissue equivalents.     

Mutants of H-ras that interfere with RAS effector function in Saccharomyces cerevisiae.

We report a class of interfering mutants of the human H-ras gene capable of inhibiting phenotypes arising from the expression of the activated RAS2 gene, RAS2val19, in the yeast Saccharomyces cerevisiae. All these mutants encode unprocessed H-ras proteins that remain in the cytoplasm. One of the mutants, H-rasarg186, was examined in detail. H-rasarg186 protein is a competitive inhibitor of RAS2val19 protein. It does not interfere with processing and membrane localization of RAS2val19, nor does it appear to compete with RAS protein for its proposed regulator, the CDC25 protein. By several criteria the RAS2val19 adenylate cyclase interaction is unaffected by H-rasarg186. We infer from our results that H-rasarg186 protein interferes with an alternative function of RAS2val19.     

Comparison of the predicted structure for the activated form of the P21 protein with the X-ray crystal structure

The predicted conformation and position of the central transforming region (residues 55–67) of the p21 protein are compared with the conformation and position of this segment in a recently determined X-ray crystal structure of residues 1–166 of this protein in the activated state bound to a nonhydrolyzable GTP derivative. We previously predicted that this segment of the protein would adopt a roughly extended conformation from Ile 55-Thr 58, a reverse turn at Ala 59-Gln 61, followed by an -helix from Glu 62-Met 67. We further predicted that this region of the activated protein occupies a position that is virtually identical to corresponding regions in the homologous purine nucleotide-binding proteins, bacterial elongation factor (EF-tu), and adenylate kinase (ADK). We find that there is a close correspondence between the conformation and position of our predicted structure and those found in the X-ray crystal structure. A mechanism for activation of the protein is proposed and is corroborated by X-ray crystallographic data.     

Gene transfer between Escherichia coli and Enterobacter aerogenes

Summary Transfer of chromosomal genes between Escherichia coli K12 and Enterobacter aerogenes was carried out by P1-mediated transduction as well as by transformation of genes cloned in vitro on plasmid vectors. The efficient expression of E. coli genes in E. aerogenes probably reflects the existance of a poor restriction system in the latter, and suggests that this strain might be useful as a recipient of genetic information from E. coli.     

The streaming of the submandibular gland II: parenchyma and stroma advance at the same velocity

Abstract Thirty young male rats aged 7 weeks, weighing 200 g, were injected with 18.5 kBq g⁻¹ (0.5 μCi g⁻¹) body weight tritiated thymidine [³H]TdR (specific activity 185 GBq). The rats were then killed in groups of five, at the following times: 1 hour, and 14, 30, 60, 90, and 120 days. Autoradiograms of sections through the submandibular gland were prepared, and the location of labelled cells in tubular and acinar cross sections was recorded. The nuclear content of each cross section was defined as its 'class'. In this numbering system, narrow tubuli, e.g. intercalated ducts are of low class, and wider tubuli, e.g. striated ducts, of high class. One hour after labelling most labelled tubular cells were found in low class cross sections, i.e. intercalated ducts and narrow granular ducts. Striated ducts were not labelled. From then onward labelled cells entered wider tubuli, e.g. striated ducts. The advancing labelled epithelium was accompanied by labelled stroma. Both cell types traversed 0.089 classes per day. In acini, labelled cells advanced in the oposite direction, starting from acinar cross sections of high class and ending in class-1 cross sections.     

The adaptation of a two-compartment cell renewal system to external demands

Summary The inner enamel epithelium (IEE) covers the labial tooth aspect as a one cell layer which, when cut sagittally, appears as a longitudinal cell column extending from the tooth origin toward the periphery. Following sudden tooth shortening, the IEE responds by an increased cell production which later declines below normal values. The perturbation affects all cell kinetic parameters; the progenitor compartment, which initially increases, diminishes in size toward end of the experiment. The cell cycle transition times, which initially decline, rise toward the end of the experiment. The mean normal daily cell production rate of 70 cell % (i.e. 70 cells are produced by 100 progenitors) increases to 111 cell % and then declines to a low of 51 cell %. The IEE response typifies the behavior of other cell renewal systems such as intestinal epithelium and epidermis.     

A quantitative description of vitellogenesis in Locusta migratoria migratorioides

During the main period of development of the oöcytes in Locusta migratoria migratorioides from 1.5 mm to 5.5 mm in length, a steady-state level of about 8 mg/ml VG (vitellogenin)² is maintained. During this period, total uptake rate of VG by the terminal oocytes was calculated to increase linearly from about 0.05 mg/hr to about 0.5 mg/hr. This increase is matched by an increase in the rate of VG synthesis, as determined by ³H-leucine incorporation rates, while the rate of synthesis of nonvitellogenic proteins at the same time remains constant.     

The influence of canavanine and related compounds on the water balance system of locusts

In vivo increase in haemolymph volume of canavanine-treated locusts substantiates our previous in vitro findings that canavanine inhibits fluid secretion by locust Malpighian tubules. Furthermore when diuretic hormone is applied in vivo after canavanine treatment haemolymph volume is drastically reduced below levels retained in locusts untreated with canavanine. Again this is in accord with canavanine potentiation of semi-isolated Malpighian tubules and enhanced fluid secretion in vitro. The response is specific to canavanine; compounds similar in structure (arginine, argininic acid, citrulline, canaline, ornithine and homoserine) have no effect on the rate of fluid secreted by Malpighian tubules. Only partial competition is obtained with uridine homoserine.     

Rapid in vitro activation of corpora allata by extracted locust brain allatotropic factor

Brains of young (newly emerged) adult female locusts (Locusta migratoria migratorioides) and of mature (> 9 days old) locusts contain an extractable allatotropic factor, soluble in 100% methanol and in distilled water. This factor stimulates juvenile hormone III (JH III) synthesis and release from corpora allata (CA) that have been excised from donor locusts and then incubated with (radiolabeled methyl)-methionine in vitro in its presence. In addition to JH III, which is the major product synthesized by the CA, other hexanesoluble, radiolabeled compounds–-more polar than JH III–-are also released when CA are incubated in vitro. The activation of CA by the allatotropic factor is rapid and quickly declines when the factor is removed from the medium. Corpora allata excised from young females are marginally active and can be activated by brain allatotropic factor to less of an extent than CA of mature locusts. The content of allatotropic factor in brains of mature locusts is higher than that ascertained in brains of young females. Allatotropic factor is also present in the corpora cardiaca.