Multiple products from the shavenbaby-ovo gene region of Drosophila melanogaster: relationship to genetic complexity

The Drosophila melanogaster shavenbaby (svb)-ovo gene region is a complex locus, containing two distinct but comutable genetic functions. ovo is required for survival and differentiation of female germ line cells and plays a role in germ line sex determination. In contrast, svb is required in both male and female embryos for the production of epidermal locomotor and sensory structures. Sequences required for the two genetic functions are partially overlapping. ovo corresponds to a previously described germ line-dependent 5.0-kb poly(A)+ mRNA that first appears in the germarium and accumulates in nurse cells during oogenesis. The 5.0-kb mRNA is stored in the egg, but it is rapidly lost in the embryos except for its continued presence in the germ line precursor pole cells. The ovo mRNA predicts a 1,028-amino-acid 110.6-kDa protein homologous with transcription factors. We have identified an embryonic mRNA, 7.1 kb in length, that contains exons partially overlapping those of the 5.0-kb poly(A)+ mRNA. The spatial distribution of this newly discovered transcript during midembryogenesis suggests that it corresponds to the svb function. The arrangement of exons common to the 5.0- and 7.1-kb mRNAs suggests that the Ovo and Svb proteins share DNA-binding specificity conferred by four Cys2-His2 zinc finger motifs but differ functionally in their capacity to interact with other components of the transcription machinery.

Effects of glucose on insulin secretion, glucokinase activity, and transgene expression in transgenic mouse islets containing an upstream glucokinase promoter-human growth hormone fusion gene

We have analyzed in organ culture the effects of glucose on glucose-induced insulin secretion, glucokinase (GK) activity, and human growth hormone (hGH) expression in pancreatic islets from transgenic mice containing an upstream GK promoter-hGH fusion gene. Freshly isolated islets from these mice had a normal insulin secretory response to glucose but showed subtle defects after culture in low or high glucose for 4 days that may have been due to the accumulation of hGH in the culture media. Islets cultured from both normal and transgenic mice had approximately a fourfold induction of GK activity in response to an increased concentration of glucose in the culture media, whereas no such change in total islet hGH production was observed. Immunocytochemical localization of hGH in islets cultured in 3 mM glucose showed a pattern similar to that in freshly isolated islets. However, after culture in 30 mM glucose, hGH immunostaining became strikingly more heterogeneous. We conclude 1) that GK-hGH transgene expression does not appear to adversely affect glucose-stimulated insulin secretion in vivo or in freshly isolated islets, 2) that glucose does not induce transgene expression, thus providing additional evidence against an effect of glucose on GK gene transcription in the islet, and 3) that glucose stimulates the co-release of hGH with insulin, thereby enhancing the heterogeneous staining pattern seen among pancreatic beta-cells.

Location of a lepidopteran specificity region in insecticidal crystal protein CryIIA from Bacillus thuringiensis

The Bacillus thuringiensis insecticidal crystal protein CryIIA has both high mosquito activity and gypsy moth activity; in contrast CryIIB, which is 87% homologous, displays no mosquito activity and has a three-fold lower gypsy moth activity. The regions responsible for specificity against gypsy moth (Lymantria dispar) and mosquito (Aedes aegypti) larvae were located by introducing MluI and XhoI sites into homologous positions within the putative domain II of both cryIIA and cryIIB genes, which divided almost equally the respective second domains into three regions. Taking advantage of naturally occurring NheI and NarI sites that border the putative domain II, a set of seven chimeric proteins were produced by exchanging all combinations of those regions between CryIIA and CryIIB. Analysis of the toxicity of these chimeric proteins demonstrated that the lepidopteran and dipteran specificity regions of CryIIA were not colinear. While the specificity region of CryIIA against mosquito larvae involved region 1 and probably also region 2, the specificity region of CryIIA against gypsy moth larvae was located within region 2.

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord

It is well-known that a large number of factors can influence the expression of neuropeptides in the nervous system. In the present study, the effects of unilateral and bilateral irradiation to the rat head and neck on the expression of neuropeptides in the innervation of the submandibular gland and in the ganglionic cells of the submandibular ganglion was examined ten days and six months after treatment. Antisera directed against enkephalin and bombesin and immunohistochemical methods were used. The effects of bilateral irradiation on the staining pattern of various neuropeptides in the cervical spinal cord were also studied. In the submandibular gland and in the submandibular ganglionic cells, there was a markedly increased neuropeptide expression ten days after bilateral treatment, as seen after staining with both antisera used, while no changes occurred after unilateral treatment. Six months after treatment, the pattern of neuropeptide expression in the submandibular gland/ganglion corresponded to that seen in controls. Irradiation did not lead to any changes in the staining pattern of neuropeptides in the spinal cord. The observations show that there is a great complexity in the susceptibility of nervous tissues to radiotherapy with respect to influences on the expression of neuropeptides.

Are the associations between Alzheimer's disease and polymorphisms in the apolipoprotein E and the apolipoprotein CII genes due to linkage disequilibrium?

Allele frequencies for polymorphisms in the apolipoprotein E and the apolipoprotein CII genes were determined in subjects of Ashkenazi Jewish origin with late-onset Alzheimer's disease and in unaffected control subjects from the same ethnic group. A significant association was observed between late-onset Alzheimer's disease and the epsilon 4 (112Cys-->Arg) allele of apolipoprotein E; however, no association was detected with apolipoprotein CII. These results suggest that the association with epsilon 4 is probably not due to linkage disequilibrium.

In vitro cytotoxicity against human cancer cell lines during pulsed magnetic field exposure

In an in vitro cell growth assay, carboplatin potency against A-431 cells increased after a 1 hour PMF (pulsed magnetic field) exposure (calculated peak field 5.2 mTesla, with an average field strength of 0.525 mTeslarms; pulses rose for 120 microseconds and then abruptly fell to neutral, and were repeated at a rate of 100 or 250 pulses per second). This potentiating effect was not observed with cisplatin or daunomycin. When cytotoxicity against HT-29 cells was measured, PMF exposure potentiated both carboplatin and daunomycin, but again, not cisplatin. Both cell types exhibited increased growth when exposed only to PMF. Exposure to PMF consistently increased the cell growth of these cancer cell lines, while only some in vitro antineoplastic agents were potentiated by PMFs.

Chemotherapy of human carcinoma xenografts during pulsed magnetic field exposure

Immune deficient mice growing xenografts of HT-29 or A-431 cell lines were treated with cisplatin, carboplatin or doxorubicin in combination with one hour of wholebody pulsed magnetic field (PMF) exposure (calculated peak field 5.2 mTesla, with an average field strength of 0.525 mTeslarms; pulses rose for 120 microseconds and then abruptly fell to neutral, and were repeated at a rate of 250 pulses per second). At 24 days, the mice in each experiment were found to have significantly (p < 0.05, ANOVA) different tumor sizes among groups. The smallest mean tumor volume was consistently found in the drug+PMF group. With A-431 tumors, the cisplatin+PMF group (T) was significantly smaller, 52% [1-(100T/C)], than the cisplatin alone group (C). In HT-29 tumors, those treated with carboplatin+PMF had the smallest tumor volume at just 34% of the carboplatin-alone group. In HT-29 tumors, the doxorubicin+PMF group was 35% of the doxorubicin alone group.

Mechanisms of action of nonglucose insulin secretagogues

Insulin release induced by nonglucose secretagogues is initiated from beta-cell by a wide variety of stimuli through specific receptors or binding sites. Activation of receptors in turn generates or enhances the cytosol levels of cAMP, cADPR, IP3, DAG, and AA. These second messengers then activate protein kinases, change the ion currents cross the cell membrane, and mobilize intracellular Ca2+, thereby increasing phosphorylated proteins in the cytosol and augmenting [Ca2+]i. These events trigger exocytotic discharge of insulin. The crucial steps in receptor-mediated stimulation-secretion coupling and their relationship to glucose-stimulated insulin release is summarized in Figure 1. At the present stage of research, the general processes of secretagogue binding to receptors, of generating second messengers, of activating several types of protein kinase, and of altering the membrane potential as well as cytosol calcium levels has been intensively studied and qualitatively clarified. However, we know little about the exact nature of substrates of different protein kinases and their function in the insulin secretion process. With the help of molecular biology and protein chemistry, we expect that this gap will be filled in the near future.

Machado-Joseph disease in pedigrees of Azorean descent is linked to chromosome 14

A locus for Machado-Joseph disease (MJD) has recently been mapped to a 30-cM region of chromosome 14q in five pedigrees of Japanese descent. MJD is a clinically pleomorphic neurodegenerative disease that was originally described in subjects of Azorean descent. In light of the nonallelic heterogeneity in other inherited spinocerebellar ataxias, we were interested to determine if the MJD phenotype in Japanese and Azorean pedigrees arose from mutations at the same locus. We provide evidence that MJD in five pedigrees of Azorean descent is also linked to chromosome 14q in an 18-cM region between the markers D14S67 and AACT (multipoint lod score +7.00 near D14S81). We also report molecular evidence for homozygosity at the MJD locus in an MJD-affected subject with severe, early-onset symptoms. These observations confirm the initial report of linkage of MJD to chromosome 14; suggest that MJD in Japanese and Azorean subjects may represent allelic or identical mutations at the same locus; and provide one possible explanation (MJD gene dosage) for the observed phenotypic heterogeneity in this disease.

In situ glucose uptake and glucokinase activity of pancreatic islets in diabetic and obese rodents

The present study evaluated the involvement of glucose transport and phosphorylation in glucose-stimulated insulin release from pancreatic islets. Using quantitative histochemical techniques, we investigated basal islet glucose content, islet glucose uptake in situ during acute extreme experimental hyperglycemia, and islet glucokinase activity in several animal models of diabetes and obesity. The basal islet glucose content in anaesthetized diabetic or obese rodents was either the same or higher than that in their relevant controls. The rate of glucose uptake of islet tissue in these animals after an i.v. glucose injection was different. The db+/db+ mouse and the obese Zucker rat exhibited significantly reduced islet glucose uptake rates. RIP-cHras transgenic mice, BHE/cdb rats and partially pancreatectomized rats showed normal islet glucose uptake rates. The activity of islet glucokinase was increased to a different degree related to the blood glucose level. All five animal models of diabetes or obesity exhibited either a delay or a reduction of insulin release in response to supra maximal glucose stimulation. Our results indicate that the impairment of glucose-induced insulin release in diabetes is not consistently associated with a reduction of islet glucose uptake nor a change of glucokinase activity.

Distribution and regulation of rab3C, a small molecular weight GTP-binding protein

We have investigated the expression and regulation of rab3C in rat tissues and rat pheochromocytoma PC12 cells by using a polyclonal antibody that specifically recognizes this protein. Rab3C was expressed in the neuroendocrine systems, as is its highly homologous family member, rab3A. Strong immunoreactivity of rab3C was also observed in testis, heart and 3 different adipose tissues. In addition, induction of neuronal differentiation in PC12 cells, which causes an increase in catecholamine secretion, also led to an increase in rab3C expression. In summary, our data demonstrate a defined pattern of rab3C expression in the rat; such expression is not limited to the neuroendocrine systems. Regulated secretion of various hormones occurs from all of these rab3C-containing tissues. Our results provide important insight into understanding the potential role of rab3C in regulated exocytosis.

Observation of optical limiting and backscattering of nanosecond laser pulses in liquid-crystal fibers

We report the recent observation of nonlinear-optical phenomena occurring in isotropic liquid-crystal-cored optical fibers, including passive all-optical self-limiting effects, stimulated backscattering, and phase conjugation. These processes occur at relatively low thresholds and short fiber lengths.

Cerebellar infarction. Analysis of 22 cases

Twenty-two cases of cerebellar infarction were diagnosed by clinical findings, computerized tomography (CT), magnetic resonance image (MRI) and autopsy. Most of the infarctions occurred in the territory of the posterior inferior cerebellar artery (18/22). The most common and earliest symptoms were dizziness or vertigo (19/22), which occurred repeatedly and were accompanied by nausea and vomiting. The symptoms and signs of cerebellar lesion such as unsteady gait, limb and/or trunk ataxia, dysarthria were also the main clinical manifestations. However, in a number of patients there were no cerebellar symptoms or signs (9/22). Rapid deterioration of consciousness suggested acute compression of the brainstem, where the prognosis would be poor. CT scan made it possible to diagnose cerebellar infarction in the patients. But CT is not a satisfactory instrument in identifying this disease. MRI without bony artifacts from the posterior fossa has much higher resolution and renders the infarction to be visualized earlier. It may be regarded as the most ideal instrument in diagnosing this disease.

Analysis of upstream glucokinase promoter activity in transgenic mice and identification of glucokinase in rare neuroendocrine cells in the brain and gut

A transgene consisting of an upstream glucokinase (GK) promoter fragment linked to coding sequences of the human growth hormone gene was expressed in certain neuroendocrine cells of the pancreas, pituitary, brain, gut, thyroid, and lungs of mice. In pancreas, the transgene was expressed in a nonuniform manner among beta cells and in a variable but substantial fraction of the other islet cell types. In pituitary, it was expressed in corticotropes, and in brain, it was expressed in cells of the medial hypothalamus. Within the gut transgene expression was detected in a subset of enteroendocrine cells of the stomach and duodenal epithelium, some of which also exhibited glucagon-like polypeptide-1 immunoreactivity. In thyroid, transgene expression was observed in C cells of neonatal animals, whereas in the lung, it was expressed among rare endocrine cells of the bronchopulmonary mucosa. RNA polymerase chain reaction analysis of human growth hormone mRNA corroborated the tissue-specific transgene expression pattern. Prompted by the finding of transgene expression in specific neuroendocrine cells, we sought to determine whether GK mRNA and GK itself was also expressed in the brain and gut, tissues not previously associated with the expression of this enzyme. Using rat tissues, GK mRNA was detected by RNA polymerase chain reaction in both the brain and intestine and was localized to specific cells in the hypothalamus and enteric mucosa by in situ hybridization. A high Km glucose phosphorylating activity was detected from isolated rat jejunal enterocytes that displayed a chromatographic elution profile identical to hepatic GK. GK immunoreactivity was detected in cells of the medial hypothalamus with many of the same cells also displaying GLUT2 immunoreactivity. Together, these studies provide evidence for upstream GK promoter activity, GK mRNA, and GK itself in certain neuroendocrine cells outside the pancreatic islet and lead us to suggest that GK may play a broader role in glucose sensing by neuroendocrine cells than was thought previously.