Characterization of K+ currents and the cAMP-dependent modulation in cultured Drosophila mushroom body neurons identified by lacZ expression

Electrophysiological analysis of cultured neurons provides a potential approach toward understanding the physiological defects that may contribute to abnormal behavior exhibited by mutants of the fruit fly Drosophila. However, its application has been restricted by an inability to identify a particular functional or anatomical subpopulation of neurons from the CNS. To study neurons composing the CNS mushroom body proposed as a center for insect olfactory learning, we utilized a Drosophila enhancer detector line that expresses a lacZ reporter gene in these neurons and identified them in acutely dissociated larval CNS cultures by vital fluorescent staining. The patch-clamp analysis suggests that whole-cell voltage-activated K+ currents can be classified into two types in identified mushroom body neurons. Type 1 current comprises a TEA-sensitive slowly inactivating current and noninactivating component while type 2 current contains a 4-AP-sensitive transient A-current and a noninactivating component. Application of cAMP analogs induced distinct modulation of type 1 and type 2 currents. Our results demonstrate that the expression of the lacZ gene and the subsequent staining do not significantly alter the different types of K+ currents. This initial characterization provides a basis for further analysis of mutations that impair learning and memory resulting from an abnormal cAMP cascade preferentially expressed in the mushroom body.

Photodegradation of TCDD in soil containing organic solvents

Studies were conducted to understand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) behaviour in the near surface zone in relation to the operating conditions: UV-intensity, temperature and exposure modes. Comparisons have been made between Oriel lamp exposure tests and sunlight exposure tests. Under Oriel lamp exposure, the convective transport of TCDD, which depends on operating temperature, was the limiting factor in the cleanup process. The product differences between Oriel exposure tests and sunlight exposure tests probably result from the difference of UV-intensities.

Sequential changes in intercellular junctions between hepatocytes during the course of acute liver injury and restoration after thioacetamide treatment

Sequential changes of gap junctions (GJs), tight junctions (TJs) and desmosomes (DSs) between hepatocytes during restorative proliferation were studied in rats after a single intraperitoneal administration of 200 mg/kg thioacetamide (TAA). Antibody against connexin 32 was used to demonstrate GJs; simultaneously the changes in TJs and DSs were studied using antibodies against 7H6 protein and desmoplakins. Propidium iodide and bromodeoxyuridine were used to recognize necrotic and proliferative cells. GJs were evenly distributed in early necrotic hepatocytes at 16 h after TAA treatment, then disappeared from necrotic and surrounding cells at 24 h. At 48 h, GJs had disappeared completely from hepatocytes in whole liver lobules, while many hepatocytes were heavily labelled with BrdU. At 72 h, GJs reappeared, firstly in perinecrotic areas. At 96 h after treatment, when the injured areas had disappeared and restorative proliferation ceased, GJs were distributed evenly throughout the lobules. Immunohistochemical observation of GJs in centrilobular, perinecrotic and periportal areas after TAA-induced hepatic necrosis was confirmed by counting the number of connexin-32-positive spots in the respective areas. TJs and DSs disappeared from necrotic cells at 24 h, but then increased between 24 and 48 h in perinecrotic areas, though the increased intensity of these junctions was more evident at 48 h. At 72 h, localization of TJs and DSs returned to normal. These results suggest that during the course of acute hepatic injury, GJs (cell-cell communication) behave differently from other intercellular junctions.

Calcium/calmodulin-dependent protein kinase II and potassium channel subunit eag similarly affect plasticity in Drosophila

Similar defects in both synaptic transmission and associative learning are produced in Drosophila melanogaster by inhibition of calcium/calmodulin-dependent protein kinase II and mutations in the potassium channel subunit gene eag. These behavioral and synaptic defects are not simply additive in animals carrying both an eag mutation and a transgene for a protein kinase inhibitor, raising the possibility that the phenotypes share a common pathway. At the molecular level, a portion of the putative cytoplasmic domain of Eag is a substrate of calcium/calmodulin-dependent protein kinase II. These similarities in behavior and synaptic physiology, the genetic interaction, and the in vitro biochemical interaction of the two molecules suggest that an important component of neural and behavioral plasticity may be mediated by modulation of Eag function by calcium/calmodulin-dependent protein kinase II.

Localization of the 7H6 antigen at tight junctions correlates with the paracellular barrier function of MDCK cells

An important function of the tight junction is to act as a selective barrier to ions and small molecules, although no molecule responsible for the barrier function has been identified. Here we report evidence that the localization of the 7H6 tight junction-associated antigen identified in our laboratory at tight junctions correlates with the barrier function of MDCK cells. MDCK cells in a confluent monolayer possessed a polarized morphology, having an apical plasma membrane and a basolateral membrane, which is separated from the former by tight junctions. MDCK cells expressed both ZO-1 and 7H6 antigen at tight junctions, which maintain a tight barrier as determined by resistance to lanthanum permeation and high transepithelial electrical resistance (TER, 1500 ohm-cm2). The 7H6 antigen disappeared as tight junctions became permeable to lanthanum with a decrease in TER (below 100 ohm-cm2) due to treatment with metabolic inhibitors (10 microns antimycin A and 10 mM 2-deoxyglucose) for 30 min, while leaving ZO-1 at the cell border. The 7H6 antigen appeared at tight junctions again as TER recovered to a high level (1500 ohm-cm2) within 3 h after withdrawal of metabolic inhibitors. In addition, we found that 7H6 antigen is a phosphorylated protein and that phosphorylation is closely related to the localization of 7H6 antigen in the area of tight junctions.

[Biodistribution and metabolism of 3H-gastrodigenin and 3H-gastrodin in mice]

The biodistribution and metabolism of 3H-gastrodigenin and 3H-gastrodin after intravenous injection were studied by the detection of their radioactivity in mice tissue; the radioactive elements of mice tissue extracts after intravenous injection of 3H-gastrodin were analyzed with thin-layer chromatography (TLC). The results demonstrated that gastrodin could penetrate through the blood-brain barrier into the brain, and it was rapidly decomposed into the gastrodigenin in brain, liver and blood. Then gastrodigenin preserved in brain and mediated its pharmacological inhibitive effects on the central nervous system. Most of the gastrodigenin and gastrodin were excreted by the kidney. The findings also suggested that gastrodin might exist in the enterohepatic circulation.

Nondetectability of restriction fragments and independence of DNA fragment sizes within and between loci in RFLP typing of DNA

We provide experimental evidence showing that, during the restriction-enzyme digestion of DNA samples, some of the HaeIII-digested DNA fragments are small enough to prevent their reliable sizing on a Southern gel. As a result of such nondetectability of DNA fragments, individuals who show a single-band DNA profile at a VNTR locus may not necessarily be true homozygotes. In a population database, when the presence of such nondetectable alleles is ignored, we show that a pseudodependence of alleles within as well as across loci may occur. Using a known statistical method, under the hypothesis of independence of alleles within loci, we derive an efficient estimate of null allele frequency, which may be subsequently used for testing allelic independence within and across loci. The estimates of null allele frequencies, thus derived, are shown to agree with direct experimental data on the frequencies of HaeIII-null alleles. Incorporation of null alleles into the analysis of the forensic VNTR database suggests that the assumptions of allelic independence within and between loci are appropriate. In contrast, a failure to incorporate the occurrence of null alleles would provide a wrong inference regarding the independence of alleles within and between loci.

Pituitary adenylate cyclase-activating polypeptide stimulates steroidogenesis and adenosine 3',5'-monophosphate accumulation in cultured rat granulosa cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel neuropeptide with considerable homology to vasoactive intestinal peptide (VIP) and GH-releasing hormone (GHRH). Because we have shown previously that VIP and GHRH stimulate steroidogenesis in cultured rat granulosa cells independently of FSH, the present studies evaluated whether PACAP also stimulates steroidogenesis and compared its effects to those of VIP and GHRH. Granulosa cells cultured for 2 days with PACAP-27, VIP, or GHRH (10(-9)-10(-6) M) showed dose-dependent increases in the accumulation of progesterone, 20 alpha-dihydroprogesterone, and estrogen. The rank order of potency for the three peptides was PACAP >> VIP > GHRH. PACAP also increased cAMP accumulation and was again more potent than VIP. In addition, all three peptides synergistically augmented FSH-stimulated progesterone and 20 alpha-dihydroprogesterone accumulation with the same rank order of potency as above; however, only the highest dose of each peptide augmented estrogen accumulation. Further studies examined the effects of various androgens on these responses. PACAP-stimulated progesterone accumulation was minimal in the absence of androstenedione, but increased up to 40-fold in its presence. Other synthetic and naturally occurring androgens produced similar increases with a rank order of potency of R1881 > testosterone = androstenedione > dihydrotestosterone. Analysis of cAMP levels indicated that by 1 h after treatment with PACAP, cAMP levels within the cells increased by 4-fold, and this response was unaltered in the presence of androstenedione; however, by 48 h, cAMP levels had markedly declined, and this response was attenuated by androstenedione. These results demonstrate that PACAP stimulates steroidogenesis and cAMP accumulation in cultured rat granulosa cells, and it is more potent than its two homologs, VIP and GHRH. Because PACAP has been shown to be present within the ovary, these data indicate that this peptide may play a role in modulating ovarian steroidogenic activity.

Evaluation of 13 short tandem repeat loci for use in personal identification applications

Personal identification by using DNA typing methodologies has been an issue in the popular and scientific press for several years. We present a PCR-based DNA-typing method using 13 unlinked short tandem repeat (STR) loci. Validation of the loci and methodology has been performed to meet standards set by the forensic community and the accrediting organization for parentage testing. Extensive statistical analysis has addressed the issues surrounding the presentation of "match" statistics. We have found STR loci to provide a rapid, sensitive, and reliable method of DNA typing for parentage testing, forensic identification, and medical diagnostics. Valid statistical analysis is generally simpler than similar analysis of RFLP-VNTR results and provides powerful statistical evidence of the low frequency of random multilocus genotype matching.

Linkage disequilibria among (CA)n polymorphisms in the human dystrophin gene and their implications in carrier detection and prenatal diagnosis in Duchenne and Becker muscular dystrophies

Four short tandem repeat loci, characterized by length polymorphisms of (CA)n repeats, have been detected within introns 44, 45, 49, and 50 of the human dystrophin gene. The predicted heterozygosities for these loci range from 72 to 93%, and observed allele numbers range from 6 to 19 in 57 normal chromosomes, revealing their high degree of polymorphism. Evidence for significant disequilibria between the loci within introns 49 and 50 is found. These data appear to be consistent with observations of recombination frequencies between these markers and the length of the intron 44 in relation to the entire region. In addition, these four loci are collectively found to be 100% informative in carrier detection/prenatal diagnosis of Becker and Duchenne muscular dystrophies (B/DMD), whereas scoring the (CA)n markers within introns 45 and 49 alone gives a 99.6% success rate.

[125I-alpha-sec-butyl-p-hydroxybenzyl alcohol receptor competitive binding assays in animal body]

Based on the receptor competitive binding assays in the mice and rat body, it has been proved that both diazepam and alpha-sec-butyl-p-hydroxybenzyl alcohol (G-018) can inhibit 125I-G-018 binding with brain benzodiazepine receptor. Inhibiting effects were obvious in the cortex, cerebellum, hippocampus and midbrain. But in the medullao blongata and hypothalamus no inhibiting effect was observed. Experimental results have demonstrated that the inhibiting effect is consistent with distribution of benzodiazepine receptor in the brain. Also, experimental results have shown no difference between in vitro and in vivo. The G-018 binding with benzodiazepine receptor has been clarified under physiologic conditions.

Paternity evaluation in cases lacking a mother and nondetectable alleles

In parentage testing the formulae for computing paternity index and exclusion probability generally ignores the presence of nondetectable alleles at the loci tested. In contrast, it is now known that even when paternity testing is done with hypervariable DNA markers, nondetectable alleles should not be ignored. This work presents simple formulae needed with this consideration, to analyze paternity evaluation from DNA markers in cases where the mother of the disputed child is unavailable for testing. It is shown that even a modest frequency of nondetectable alleles (e.g., 2-5% per locus) may have a substantial impact on the paternity index when the child and/or the alleged father exhibits a single-banded DNA profile at a locus. Use of such formulae can generate a high probability of exclusion and a high paternity index when multiple independently segregating hypervariable DNA markers are used.

Sequential decrease in tight junctions as revealed by 7H6 tight junction-associated protein during rat hepatocarcinogenesis

A sequential decrease in the number of hepatocyte tight junctions during the course of rat hepatocarcinogenesis was demonstrated by immunohistochemistry with a new 7H6 monoclonal antibody generated in our laboratory. Semiquantitative analysis by confocal laser scanning microscopy revealed that the expression of 7H6 antigen was reduced in hyperplastic foci, hyperplastic nodules and hepatocellular carcinomas (HCC) to 43%, 28% and 25%, respectively, compared to corresponding normal liver tissues. 7H6 antigen was scarce in HCC with a trabecular pattern, whereas it was expressed intensely at the apical and basolateral membrane of HCC with a glandular pattern. Immunoblot analysis of 7H6 expression in hepatocellular carcinomas showed a decrease roughly coincident with that shown by immunohistochemistry. These results indicated, for the first time, that tight junctions decrease progressively during carcinogenesis, leading to disruption of cellular polarity and cellular adhesiveness.

Vascular architecture of the human optic chiasma and bitemporal hemianopia

The blood supply system of the optic chiasma was studied in 85 fresh human specimens using various histological and anatomical methods. Computer image analysis and ultrastructural examinations of the microvessel in 58 fetal specimens were also conducted. The authors found that the medial portion of the chiasma is a weak point in the microcirculation network. This weak point is apt to be disturbed first and become ischemic, causing disorders of the crossing optic nerve fibers and resulting in characteristic bitemporal visual field defects. SEM studies showed no ultrastructural difference between the capillaries at the medial and lateral portions of the chiasma. It was concluded that: 1) No special artery supplies the median chiasma the weak point of microcirculation at the median chiasma is due to its relatively scanty capillary distribution; 2) "lateral chiasma arteries" could provide a better blood supply to the lateral fibers and thus the nasal quadrantic visual field could be preserved in many late stages of visual field defect in sellar region tumors; 3) cases with pituitary microadenoma which is not sufficiently large to press the chiasma but involves bitemporal visual field defect are due to the tumor receiving "shunt-flow" (stealing blood) from the chiasma through the peri-infundibulum plexus.

Temporal averaging for quantification of lumen dimensions in intravascular ultrasound images

Quantitative analysis of arterial dimensions from high frequency intravascular ultrasound images (30 MHz) may be hampered by strong blood scattering. Replacement of blood by saline is one method to provide a clear view of the arterial lumen; another method is that of temporal averaging of successive ultrasound images. The accuracy of this latter method was tested by comparing the lumen area measurements on the temporal-averaged image, with the data of the same cross-section obtained from the single-frame and saline-filled images. The mean lumen area measured on the temporal-averaged images was similar to that measured on the single-frame images (mean difference: -0.02 +2- 1.16 mm2; p = ns). The mean lumen area of the saline-filled images was 8% larger than the values obtained from the temporal-averaged and single-frame images (mean difference: -1.14 +/- 0.85 mm2, p < 0.05), probably due to the difference in sound velocity between saline and blood. Intraobserver variation in the averaging method were 2.4 times smaller than the measurements of the single-frame images and close to the data obtained by saline injection (variation coefficient: single-frame: 8.8%; temporal-averaged: 3.6%; saline-filled: 2.9%). It is concluded that analysis from temporal-averaged images is more efficient, enabling accurate and reproducible measurement of the luminal dimensions from images containing blood scattering echoes. This technique is suitable to replace the laborious saline injection method and facilitates off-line quantitative analysis.

Statistical power of an exact test of Hardy-Weinberg proportions of genotypic data at a multiallelic locus

A computer algorithm for numerical evaluation of the statistical power of an exact test of Hardy-Weinberg genotypic proportions (HWP), developed here, indicates that the power is dependent on the number of segregating alleles as well as allele frequencies. While low levels of departure from the null hypothesis are difficult to detect from single-locus data, should such deviation be due to population substructuring, multiple loci, at each of which the number of segregating alleles is large (as seen with hypervariable loci), may easily detect even low levels of departure from HWP. Undetected small levels of departure may still provide conservative estimates of genotype frequencies from allele frequency data, following the current practice in forensic genetics.

Modulation of different K+ currents in Drosophila: a hypothetical role for the Eag subunit in multimeric K+ channels

We examined the role of the ether a go-go (eag) gene in modulation of K+ currents and the possibility of its protein product Eag as a subunit in the heteromultimeric assembly of K+ channels by voltage-clamp analysis of larval muscle membrane currents. Previous DNA sequence studies indicate that the eag gene codes for a polypeptide homologous to, but distinct from, the Shaker (Sh) K+ channel subunits (Warmke et al., 1991), and electrophysiological recordings revealed allele-specific effects of eag on four identified K+ currents in Drosophila larval muscles (Zhong and Wu, 1991). Further studies of eag alleles indicated that none of the eag mutations, including alleles producing truncated mRNA messages, eliminate any of the four K+ currents, and that the mutational effects exhibit strong temperature dependence. We found that both W7, an antagonist of Ca2+/calmodulin, and cGMP analogs modulated K+ currents and that their actions were altered or even abolished by eag mutations. These results suggest a role of eag in modulation of K+ currents that may subserve integration of signals at a converging site of the two independent modulatory pathways. The Sh locus is known to encode certain subunits of the IA channel in larval muscle. The existence of multiple eag and Sh alleles enabled an independent test of the idea of Eag as a K+ channel subunit by studying IA in different double-mutant combinations. An array of allele-specific interaction between eag and Sh was observed, which reflects a close association between the Sh and eag subunits within the IA channel. Taken together, our data strengthen the possibility that the eag locus provides a subunit common to different K+ channels. The role of the eag subunit for modulating channels, as opposed to that of Sh subunits required for gating, selectivity, and conductance of the channel, suggest a combinatorial genetic framework for generating diversified K+ channels.

Differential modulation of potassium currents by cAMP and its long-term and short-term effects: dunce and rutabaga mutants of Drosophila

The cAMP concentration in Drosophila is increased by mutations of the dunce (dnc) gene and decreased by mutations of the rutabaga (rut) gene. Such mutants provide a unique means for exploring the role of cAMP in functional and developmental regulation of membrane currents. Four distinct K+ currents have been identified in Drosophila larval muscle fibers, i.e. the voltage-activated transient IA and delayed IK and the Ca(2+)-activated fast ICF and slow ICS. Results from our voltage-clamp studies indicated that both IA and IK were increased in dnc alleles. Normal muscle fibers treated with dibutyryl-cAMP showed a similar increase of IA, but no significant effect on IK. In contrast to the dnc alleles, the rut mutations appeared to enhance ICS greatly while leaving the amplitude of other currents largely unchanged. In addition, the dibutyryl-cAMP-induced increase in IA was not observed in rut fibers. Caffeine and W7, which are known to interfere with several second messenger pathways, also modulated K+ currents in larval muscle fibers. The currents in dnc and rut fibers showed strikingly altered responses to caffeine and W7. The results demonstrate that the various K+ currents in Drosophila muscles are affected by altered cAMP cascades in the mutants. The fact that not all dnc and rut mutant defects can be mimicked or reversed by acute application of cAMP suggests that long-term modulation of K+ currents by cAMP may involve mechanisms distinct from the short-term effect of cAMP.

On allele frequency computation from DNA typing data

Forensic applications of DNA typing data require the estimation of the frequencies of all observed alleles, which is currently done by a fixed set of groupings (binning) of alleles in a database. Recently it's validity has been questioned on the ground that when a DNA fragment size is close to a bin boundary, the frequencies of all adjacent bins should be added. On the contrary, the current forensic database indicates that when the match window of a DNA fragment overlaps 2 bins, it is enough to consider the bin with the larger frequency, and this never underestimates the frequency within the match interval with the current choice of fixed-bin widths. On average, the current fixed-bin procedure yields an allele frequency at least 2-fold higher than that of a floating-bin.

Monoclonal antibody 7H6 reacts with a novel tight junction-associated protein distinct from ZO-1, cingulin and ZO-2

The tight junction is an essential element of the intercellular junctional complex; yet its protein composition is not fully understood. At present, only three proteins, ZO-1 (Stevenson, B. R., J. D. Siliciano, M. S. Mooseker, and D. A. Goodenough. 1986. J. Cell Biol. 103:755-766), cingulin (Citi, S., H. Sabanay, R. Jakes, B. Geiger, and J. Kendrick-Jones. 1988. Nature (Lond.). 333:272-275) and ZO-2 (Gumbiner, B., T. Lowenkopf, and D. Apatira. 1991. Proc. Natl. Acad. Sci. USA. 88:3460-3464) are known to be associated with the tight junction. We have generated a monoclonal antibody (7H6) against a bile canaliculus-rich membrane fraction prepared from rat liver. This 7H6 antigen was preferentially localized by immunofluorescence at the junctional complex regions of hepatocytes and other epithelia, and 7H6-affiliated gold particles were shown electron microscopically to localize at the periphery of tight junctions. Immunoblot analysis of a bile canaliculus-rich fraction of rat liver using 7H6, anti-ZO-1 antibody (R26.4C), and anti-cingulin antibody revealed that 7H6 reacted selectively with a 155-kD protein, whereas R26.4C reacted only with a 225-kD protein. Anti-cingulin antibody reacted solely with 140 and 108-kD proteins, indicating that the protein recognized by 7H6 is immunologically different from ZO-1 and cingulin. Immunoprecipitation of detergent extracts obtained from metabolically labeled MDCK cells with R26.4C coprecipitated a 160-kD protein, which corresponds to ZO-2, with ZO-1. However, 7H6 did not react with the 160-kD protein. These results strongly suggest that the 7H6 antibody recognizes a novel tight junction-associated protein different from ZO-1, cingulin and ZO-2.

Effect of balloon angioplasty on femoral artery evaluated with intravascular ultrasound imaging

BACKGROUND

Intravascular ultrasound was used to assess the immediate effect of balloon angioplasty on the superficial femoral artery.

METHODS AND RESULTS

In 16 consecutive patients, corresponding ultrasonic cross sections (n = 72) before and after balloon angioplasty were qualitatively and quantitatively analyzed. The qualitative data were compared with angiographic findings. Before intervention, the angiographically demonstrated obstructive lesions were confirmed by intravascular ultrasound. Ultrasound enabled discrimination between soft (n = 43) and hard (n = 29) lesions, as well as between eccentric (n = 57) and concentric (n = 15) lesions. After balloon angioplasty, the presence of a dissection assessed angiographically in 14 patients was confirmed by intravascular ultrasound. Additional morphological information provided by ultrasound included plaque rupture in 14 patients and internal lamina rupture in six patients. Quantitative ultrasound data revealed an increase in free lumen area from 9.7 +/- 4.7 to 18.3 +/- 7.0 mm2 (p less than or equal to 0.01), an increase in minimal lumen diameter from 2.8 +/- 0.7 to 3.6 +/- 1.2 mm (p less than or equal to 0.01), and an increase in media-bounded area from 21.7 +/- 5.4 to 28.3 +/- 5.8 mm2 (p less than or equal to 0.01). The lesion area for the majority of cases (n = 32) remained unchanged (13.0 +/- 4.9 mm2 versus 12.9 +/- 4.6 mm2), or the lesion disappeared partially (from 9.1 +/- 0.9 to 4.3 +/- 1.4 mm2, n = 4, p less than or equal to 0.01) or totally (from 10.1 +/- 4.2 to 0 mm2, n = 6). Stretching of the arterial wall was further evidenced by medial thinning from 0.55 +/- 0.19 to 0.34 +/- 0.11 mm (p less than or equal to 0.01).

CONCLUSIONS

Luminal enlargement by balloon dilatation is achieved primarily by overstretching the arterial wall, with the lesion volume remaining practically unchanged. Overstretching is accompanied almost always by dissection and plaque rupture and occasionally by an internal lamina rupture.