91 Management and Outcomes of Appendicitis in The Pre-COVID-19, COVID-19 And Post-COVID-19 Periods

Aim

The COVID-19 pandemic resulted in an upheaval of national surgical guidance on appendicitis, which has previously favoured surgical over conservative approaches. We analysed how these guidelines altered management and outcomes of appendicitis.

Method

A retrospective cohort study at Heartlands Hospital, Birmingham of all appendicitis admissions around and during the first COVID-19 peak was conducted, with analysis of electronic patient records using the acute surgical worklist.

Results

48 admissions for appendicitis during the two-month period from 01/02/20 to 25/03/20 prior to the COVID-19 peak and 28 admissions in the two months during the peak itself from 30/03/20 to 24/05/20 were identified. Prior to the COVID-19 peak, a lower proportion of cases was managed conservatively (18.8%) compared to the latter (67.9%, p < 0.0001). This change also coincided with a switch from laparoscopic to open approaches in those managed surgically. We studied a further period post-COVID-19 peak from 01/06/20 to 26/07/20, where proportions of patients managed conservatively versus surgically did not significantly change following the COVID-19 peak, although surgical preference reverted from open to laparoscopic approaches. During the COVID-19 period, a reduced length of stay was seen in cases managed conservatively (1.65 days) compared to those managed surgically (4 days, p = 0.024). Differences in readmission rates were not statistically significant.

Conclusions

A reduction in numbers of appendicitis presentations as well as a switch to conservative approaches was seen during COVID-19. These findings furthermore support non-inferiority of conservative over open surgical approaches in most appendicitis cases at a time where laparoscopy was deemed unfeasible.

Osteochondroma on the cranial aspect of the distal radial metaphysis causing tenosynovitis of the extensor carpi radialis tendon sheath in a horse

CASE REPORT

A 3-year-old Thoroughbred gelding was presented with a grade 3/5 lameness of the right forelimb and effusion of the extensor carpi radialis tendon sheath (ECRTS). Radiographic and ultrasonographic examinations revealed an osteochondroma on the cranial aspect of the distal radius projecting into the fibrous lining of the ECRTS. An open surgical approach was used to remove the osteochondroma and some of the proliferative synovial tissue.

CONCLUSION

Six months after surgery the clinical signs had resolved and the horse raced successfully.

Evaluation of a modification of the McKinnon technique to correct urine pooling in mares

The urethral fold of 30 mares was split transversely into dorsal and ventral shelves, and the ventral shelf was used to help create a urethral extension. The dorsal shelf was stretched caudally and sutured to the roof of the extension so that it covered at least the cranial half of the extension. For 20 mares, a relaxing, vaginal incision was created cranial to the external urethral orifice to enable the dorsal shelf to be retracted further caudally. Ten of the 30 mares (33.3 per cent) developed a defect, but none developed a defect in that portion covered by the dorsal shelf of the urethral fold. Two of the 30 mares (6.7 per cent) developed a defect so small that the defect could be detected only by inserting a dye, under pressure, into the tunnel. The total number of mares that developed only a grossly visible and palpable defect was eight of 30 (26.6 per cent). Four of the 10 mares that did not receive the relief incision and six of 20 mares that did receive the relief incision developed a defect in the extension. Modifying the McKinnon technique by transversely splitting the urethral fold and retracting the dorsal half helps prevent a defect from forming in the cranial portion of the extension. The dorsal shelf can be retracted further caudally by creating a relief incision on the floor of the vagina.

The development and activity-dependent expression of aggrecan in the cat visual cortex

The Cat-301 monoclonal antibody identifies aggrecan, a chondroitin sulfate proteoglycan in the cat visual cortex and dorsal lateral geniculate nucleus (dLGN). During development, aggrecan expression increases in the dLGN with a time course that matches the decline in plasticity. Moreover, examination of tissue from selectively visually deprived cats shows that expression is activity dependent, suggesting a role for aggrecan in the termination of the sensitive period. Here, we demonstrate for the first time that the onset of aggrecan expression in area 17 also correlates with the decline in experience-dependent plasticity in visual cortex and that this expression is experience dependent. Dark rearing until 15 weeks of age dramatically reduced the density of aggrecan-positive neurons in the extragranular layers, but not in layer IV. This effect was reversible as dark-reared animals that were subsequently exposed to light showed normal numbers of Cat-301-positive cells. The reduction in aggrecan following certain early deprivation regimens is the first biochemical correlate of the functional changes to the γ-aminobutyric acidergic system that have been reported following early deprivation in cats.

Brain enriched hyaluronan binding (BEHAB)/brevican increases aggressiveness of CNS-1 gliomas in Lewis rats

Gliomas are the most common primary intracranial tumors. One extracellular matrix component that has been implicated in glial tumor biology is brain enriched hyaluronan binding (BEHAB)/brevican. In this study, the CNS-1 rat glioma cell line was transfected with a vector containing either a full-length BEHAB/brevican cDNA, a 5' insert encoding the NH(2)-terminal BEHAB/brevican cleavage product, or a 3' insert encoding the COOH-terminal cleavage product. As a control, CNS-1 cells were transfected with green fluorescent protein. Rats with intracranial grafts of BEHAB/brevican-transfected CNS-1 cells displayed significantly shorter survival times than did rats with CNS-green fluorescent protein intracranial grafts (P < 0.001). Histological examination showed that the BEHAB/brevican-transfected tumors were just as, if not more, aggressive than control tumors, even though the BEHAB/brevican tumors had been growing for only approximately two-thirds the time as long as control tumors. These data suggest that up-regulation and proteolytic cleavage of BEHAB/brevican increase significantly the aggressiveness of glial tumors. It will be important to investigate the effect of inhibiting cleavage of BEHAB/brevican in these cells and to determine the therapeutic potential of inhibiting BEHAB/brevican cleavage in gliomas.

Differential distribution of the G protein gamma3 subunit in the developing zebrafish nervous system

G proteins play an essential role in the transduction and propagation of extracellular signals across the plasma membrane. It was once thought that the G protein alpha subunit was the sole regulator of intracellular molecules. The G protein betagamma complex is now recognized as participating in many signaling events. While screening a zebrafish cDNA library to identify members of the protein 4.1 superfamily (Kelly, G.M., Reversade, B., Biochem. Cell Biol. 75 (1997), 623), we fortuitously identified a clone that encodes a zebrafish G protein gamma subunit. The 666 nucleotides of the zebrafish G protein gamma subunit cDNA encodes a polypeptide of 75 amino acids with high degree of homology to human, bovine, rat and mouse gamma subunits. BLAST search analysis of GenBank revealed that the zebrafish gamma subunit is 93% identical and 97% similar to the mammalian gamma3 subunit. The gamma3 gene was mapped to the zebrafish linkage group 21, approximately 10.76 cRays from bf, a gene with sequence homology to the human properdin factor gene. RT-PCR and in situ hybridization analyses first detected gamma3 mRNA during late somitogenesis, where it was expressed preferentially in the Vth cranial nerve, the forebrain and in ventrolateral regions of the mid- and hindbrain including the spinal cord. The ability of the zebrafish gamma3 subunit to form a signaling heterodimeric complex with a beta subunit was tested using a human beta2 subunit. The gamma3 formed a heterodimer with beta2 and the complex was capable of binding calmodulin in a calcium-dependent manner. Overexpression of the beta2gamma3 complex in zebrafish embryos lead to the loss of dorsoanterior structures and heart defects, possibly owing to an up-regulation of mitogen-activated protein kinase activity and/or decline in protein kinase A signaling. Together, these data imply that a betagamma heterodimer plays a role in signal transduction events involving G protein coupled receptors and that these events occur in specific regions in the nervous system of the developing zebrafish.

Ran binding protein RanBP1 in zebrafish embryonic development

Ran, which functions in nucleocytoplasmic transport and mitosis, binds to and is regulated in part by RanBP1. We have identified a zebrafish RanBP1 cDNA and report that it encodes for a polypeptide of 233 amino acids with considerable similarity to human and Xenopus RanBP1, despite the fact that it is 10% longer due to an extension at its carboxy terminus. RanBP1 mRNA is present as a maternal transcript and is expressed ubiquitously throughout the developing embryo. At the protein level, RanBP1 is present at all embryonic stages. Surprisingly, the ectopic overexpression of the protein had no obvious effect on embryogenesis. Attempts were also made to down-regulate RanBP1 activity by RNA interference. Injecting double-stranded RNA augmented both the mortality rate and the frequency of induced defects. Specific defects accompanied by changes in RanBP1 expression were not seen, leading us to propose that RNAi is not a reliable method for deregulating the activity of constitutively expressed genes, like RanBP1, in zebrafish. Mol. Reprod. Dev. 59:235-248, 2001.

New thoughts on the role of the beta-gamma subunit in G-protein signal transduction

Heterotrimeric G proteins are involved in numerous biological processes, where they mediate signal transduction from agonist-bound G-protein-coupled receptors to a variety of intracellular effector molecules and ion channels. G proteins consist of two signaling moieties: a GTP-bound alpha subunit and a beta-gamma heterodimer. The beta-gamma dimer, recently credited as a significant modulator of G-protein-mediated cellular responses, is postulated to be a major determinant of signaling fidelity between G-protein-coupled receptors and downstream effectors. In this review we have focused on the role of beta-gamma signaling and have included examples to demonstrate the heterogeneity in the heterodimer composition and its implications in signaling fidelity. We also present an overview of some of the effectors regulated by beta-gamma and draw attention to the fact that, although G proteins and their associated receptors play an instrumental role in development, there is rather limited information on beta-gamma signaling in embryogenesis.

The Translocon-Associated Protein beta (TRAPbeta) in zebrafish embryogenesis. I. Enhanced expression of transcripts in notochord and hatching gland precursors

The normal translocation of nascent polypeptides into the lumen of the endoplasmic reticulum (ER) is thought to be aided in part by a translocon-associated protein (TRAP) complex consisting of 4 protein subunits. The association of mature proteins with the ER and Golgi, or other intracellular locales, such as lysosomes, depends on the initial targeting of the nascent polypeptide to the ER membrane. A similar scenario must also exist for proteins destined for secretion. We have identified a member of the TRAP complex using a two hybrid screen to isolate proteins that bind to zebrafish (Danio) Ran binding protein 1. The polypeptide predicted from the largest open reading frame contains 183 amino acids with a 86 and 87% sequence identity to the TRAPbeta subunits in human and chicken, respectively. Sequence analysis identified a cleavable amino-terminal signal peptide in the zebrafish TRAPbeta subunit and a region of the protein spans the membrane of the endoplasmic reticulum. A reverse transcriptase-polymerase chain reaction assay showed that TRAPbeta mRNA is expressed in the developing zebrafish embryo. TRAPbeta mRNA is maternally supplied to the egg and is expressed constitutively throughout development and in the adult. This pattern of expression indicates that the message encoding part of the machinery targeting nascent polypeptides to the ER lumen is available at the onset of embryogenesis when the rate of translation increases exponentially over that occurring in the oocyte. In situ hybridization was used to test whether or not TRAPbeta transcripts might become localized and/or enriched in the developing embryo. Homogeneous staining is seen in the blastula and early gastrula stages. At mid-to-late gastrula stages, however, the message becomes enriched in the developing notochord and polster, or hatching gland rudiment. The TRAPbeta gene, mapped using the LN54 mouse-zebrafish radiation hybrid panel to linkage group 19, resides next to a gene (Z15451) which has sequence homology to notch2 and vascular endothelial growth factor. TRAPbeta, however, does not appear to belong to a group of genes which are syntenic with orthologues or paralogues on human chromosomes.

Blockade of pilocarpine-induced cerebellar phosphoinositide hydrolysis with metabotropic glutamate antagonists: evidence for an indirect control of granule cell glutamate release by muscarinic agonists

The ability in vivo of the muscarinic agonist, pilocarpine, to increase phosphoinositol (PI) hydrolysis in lithium pretreated rats was investigated by measuring the accumulation of [(3)H]inositol phosphates (IP). As expected, 20 mg/kg s.c. pilocarpine, a muscarinic agonist, increased PI hydrolysis in the striatum, frontal cortex and hippocampus. Somewhat surprisingly, an increase in IP was also found in the cerebellar homogenates. In all four tissues the pilocarpine-induced effect could be completely inhibited by pretreatment with the muscarinic antagonist scopolamine (1.2 mg/kg i. p.). It was also found that the cerebellar but not the hippocampal pilocarpine-induced rise in PI hydrolysis could be blocked by the metabotropic glutamate (mGlu) receptor antagonist, LY341495 (100 nmol, i.c.v.). The same dose of LY341495 was found to also block both the cerebellar and hippocampal increase in IP formed by stimulation with the group I mGlu receptor agonist 3, 5-dihydroxyphenylglycine (1 micromol, i.c.v.). Given this data and the current information on the distribution of muscarinic and mGlu receptors in the cerebellum, it is suggested that these results may be a reflection of pilocarpine acting at M(2) receptors to indirectly increase glutamate release from parallel fibers by inhibition of gamma-aminobutyric acid-releasing Golgi cells.

Intracranial injury acutely induces the expression of the secreted isoform of the CNS-specific hyaluronan-binding protein BEHAB/brevican

Hyaluronan (HA) plays an important role in tissue reorganization in response to injury. The mechanisms by which HA participates in these processes are likely to include HA-binding proteins. Previously, we reported the cloning and initial characterization of a central nervous system (CNS)-specific HA-binding protein, BEHAB (brain enriched hyaluronan binding), which was independently cloned in another laboratory and named brevican. BEHAB/brevican mRNA is expressed in the ventricular zone coincident with the initial proliferation and migration of glial cells and in surgical samples of human glioma, where glial-derived cells proliferate and migrate. To determine whether BEHAB/brevican is also expressed during the cellular proliferation and migration associated with CNS injury, we have examined BEHAB/brevican expression during reactive gliosis. BEHAB/brevican occurs as secreted and cell-surface, glycosylphosphatidylinositol (GPI)-anchored, isoforms. The secreted, but not the GPI-anchored, isoform is up-regulated in response to a stab wound to the adult rat brain. The temporal regulation and spatial distribution of BEHAB/brevican expression parallel the gliotic response and the expression of the intermediate filament protein nestin. The up-regulation of BEHAB/brevican in response to CNS injury suggests a role for this extracellular matrix molecule in reactive gliosis. Glial process extension, a central element in the glial response to injury, may require the reexpression of both cytoskeletal and matrix elements that are normally expressed during the glial motility seen in the immature brain.

Phosphoinositide hydrolysis in vivo with group I metabotropic glutamate receptor agonists

The present report describes the effect of mGluR agonists and antagonists administration on phospholipase C activation by measuring accumulation of [3H] inositol monophosphates (IP) in rats pre-labeled with [3H]myo-inositol (i.c.v. 24 h pre-treatment). The levels of accumulated [3H]IP were then determined from clarified tissue homogenates using ion-exchange chromotography. Following lithium chloride treatment (10 mg/kg, s.c.), (R/S)-3, 5-dihydroxyphenylglycine (DHPG), a selective group I mGluR agonist was found to dose-dependently cause a maximal increase in the levels of [3H]IP at 0.3 to 3 micromol/8 microliter i.c.v. with lower doses resulting in less efficacious or no responses. This effect was temporal-dependent reaching a plateau at 2 h. The DHPG-induced increases in [3H]IP were most pronounced in the hippocampus where a 3- to 5-fold increase above vehicle was consistently found, but significant approximately 2-fold increases were also seen in the cerebellum, striatum and frontal cortex. The mixed group I and II agonist, (1S,3R)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (1S, 3R-t-ACPD), similarly resulted in dose-dependent increases in [3H]IP levels with doses of 1 to 3 micromol i.c.v. Furthermore, this effect was enantiomer specific since the less active 1R,3S-t-ACPD failed to alter phosphoinositol hydrolysis. Administration of the selective mGluR5 agonist (R/S)-2-chloro-5-hydroxyphenyl-glycine (CHPG) resulted in a dose-dependent increase in hippocampal but not cerebellar levels of [3H]IP, consistent with the receptor distribution of the two group I mGluRs. The Group II agonist LY354740 (1S,2S,5R,6S-2-aminobicycl[3.1.0]hexane-2,6-dicarboxylate monohydrate) and the group III agonist L-AP4 (L-(+)-2-amino-4-phosphonobutyric acid) failed to alter the levels of [3H]IP. LY341495 (2S-2-amino-2-(1S, 2S-2-carboxycycloprop-1-yl)-3-(xanth-9-yl)propanoic acid) is a nM potent Group II antagonist. However, LY341495 has also been found to have microM potency in inhibiting mGluR1 and 5. The stimulation of [3H]PI hydrolysis by 1 micromol DHPG was dose-dependently blocked by co-administration of the mGluR antagonists, LY341495 at doses that are constant with an interaction at Group I mGluR's. Taken together these results suggest that stimulation of group I mGluRs results in measurable increases in PI hydrolysis in vivo. This method could be quite useful in determining the doses and routes of administration of agonists and antagonists that are required to interact with group I mGluRs.

BEHAB/brevican: a brain-specific lectican implicated in gliomas and glial cell motility

Several recent findings have advanced our understanding of the composition and function of the brain extracellular matrix (ECM). BEHAB/brevican, a recently identified CNS-specific proteoglycan, is a component of the brain ECM and is upregulated during glial cell motility. It is expressed at high levels during development, in response to injury, and in primary brain tumors. Cleavage of the BEHAB/brevican protein may increase invasion of tumor cells.

Characterization of a cDNA encoding a novel band 4.1-like protein in zebrafish

Membrane skeleton protein 4.1 and other members of a family of proteins that link the cytoskeleton to the plasma membrane may play an integral role in cell communication during development. The polymerase chain reaction and degenerate oligodeoxynucleotide primers to consensus sequences in the putative membrane-binding domain of the protein 4.1 superfamily were used to isolate cDNAs encoding members of the zebrafish protein 4.1 family. Zebrafish stage- and tissue-specific first strand cDNA was used in the PCR. After the reaction, amplicons of the predicted size were sequenced to confirm their relationship to the protein 4.1 superfamily. One cDNA, with a high degree of similarity to a mouse novel band 4.1-like cDNA, was used to probe a zebrafish adult brain library. A 2.4-kb cDNA was isolated and found to encode a 619 amino acid polypeptide homologous to mouse novel band 4.1-like protein 4. Zebrafish nbl4 mRNA is maternally supplied and is expressed throughout embryogenesis. In adults, nbl4 is found in the ovary, eye, heart, and brain, but not in gut or skeletal muscle. When synthetic nbl4 mRNA is translated in vitro it binds calmodulin in a calcium-dependent manner. These data indicate that zebrafish nbl4 is a maternal transcript owing to its presence before the midblastula transition, and it is present later on in specific adult structures. The ability to bind calmodulin would suggest that the function of nbl4 protein may be potentially regulated via a calcium-calmodulin dependent mechanism.

The zebrafish's swim to fame as an experimental model in biology

The zebrafish has long been the favorite organism in many scientific disciplines. Although its attributes as a model were expounded for many years and thus were no secret, the zebrafish sat in the wings while other more popular vertebrates such as chick, amphibians, and mouse were examined at length. We cannot say there was a resurgence in popularity, but more an explosion of research utilizing the zebrafish beginning in the late 1970s when investigators at the University of Oregon began using it as their model in neuroscience. Prior to this reawakening, the zebrafish was one of the significant organisms in the study of teratology and toxicology, development, and, to some extent, behavior. Recently, however, the field of zebrafish genetics has gained immense popularity and success, in part owing to the fact that zebrafish are diploid and are amenable to genetic manipulations. Here we present an overview of the multidisciplinary research that has laid some of the foundation of our present understanding of the biochemical, cell biological, and molecular genetic events accompanying zebrafish development.

Phospholipase C-beta1 is present in the botrysome, an intermediate compartment-like organelle, and Is regulated by visual experience in cat visual cortex

Monoclonal antibody Cat-307 identifies a 165 kDa neuronal protein expressed in the cat visual cortex during the period of sensitivity to alterations in visual experience (). Dark-rearing, which prolongs the sensitive period, also prolongs the expression of the Cat-307 protein. The Cat-307 protein localizes to an organelle, here called the botrysome (from the Greek botrys, cluster of grapes), that is located between the endoplasmic reticulum (ER) and Golgi apparatus. The botrysome is composed of small ring-shaped profiles with electron-dense coats. The size and morphology of the rings and their coats are similar to those described for ER to Golgi transport vesicles. Biochemically, the Cat-307 protein cofractionates with microsomes and partitions with subunits of the coatomer proteins that coat ER-to-Golgi transport vesicles. Partial amino acid sequencing reveals that the Cat-307 protein is phospholipase C-beta1, the G-protein-dependent phosphodiesterase that hydrolyses phosphatidylinositol 4,5 biphosphate into inositol 1,4,5 triphosphate and diacylglycerol after the stimulation of a variety of neurotransmitter receptors at the cell surface. These results suggest a role for phospholipase C-beta1 and the botrysome in developmental plasticity and provide a possible link between receptor activation at the cell surface and protein transport during neuronal development.

Identification and characterization of novel developmentally regulated proteins in rat spinal cord

We previously used 2-dimensional (2-D) gel electrophoresis to identify novel proteins that may be involved in the genesis of the mammalian nervous system [1]. Several novel proteins that were up- or down-regulated coincident with neurogenesis and neuronal migration in rat neocortex were identified. To further investigate the expression of some of these developmentally regulated proteins during a comparable period in spinal cord development, 2-D electrophoresis is used to study their regulation in the crude membrane and soluble fractions of spinal cord at embryonic day 12 (E12) and embryonic day 21 (E21). This analysis indicates that 7 of the proteins that exhibited large changes in their synthesis in cerebral cortex between embryonic day 14 (E14) and embryonic day 21 (E21) demonstrate similar up- or down-regulation during spinal cord neurogenesis. However, two proteins are restricted in their expression or developmental regulation. One of these, 667-800, appears cortex-specific, while the up-regulation of protein SC.1 appears to be spinal cord specific. Several of these proteins also appear to be enriched in both the cortex and spinal cord relative to non-neural tissues (117, 162, 182, 310 [TOAD-64], 667-800) and may be neural specific. To further characterize its expression, one of these neural-specific, up-regulated proteins, TOAD-64 (protein 310) [2-4], is studied throughout embryonic and postnatal spinal cord development using peptide-specific polyclonal antibodies. As suggested by the 2-D gel analysis and the previously reported expression pattern in cerebral cortex [3], TOAD-64 is transiently expressed in postmitotic spinal cord neurons early in their development and sharply down-regulated after the second postnatal week. In the adult spinal cord, TOAD-64 expression is remarkably restricted to a subset of primary afferents to the spinal cord. This expression pattern, coupled with its recently discovered homology to two proteins implicated in axon pathfinding in the chick and nematode [5,3], suggests that TOAD-64 may have a fundamental role in axon pathfinding.

BEHAB (brain enriched hyaluronan binding) is expressed in surgical samples of glioma and in intracranial grafts of invasive glioma cell lines

Malignant gliomas aggressively invade the surrounding normal brain, whereas brain metastases of nonglial tumors do not. The invasive behavior of gliomas may be mediated by tissue- or tumor-specific extracellular proteins. mRNA for the brain-specific extracellular brain enriched hyaluronan-binding protein (BEHAB) is not detectable in normal adult human cortex or in any nonglioma tumor examined. BEHAB is consistently expressed in surgical samples of glioma (n = 27). Glioma cell lines maintained under standard cell culture conditions or grown as s.c. tumors do not express BEHAB. When grown as intracranial grafts, glioma cell lines that invade the brain express BEHAB, whereas noninvasive cell lines do not. BEHAB is a unique and selective marker for glioma and may play a role in tumor invasion.

Cloning and characterization of a cDNA encoding the collagen-binding stress protein hsp47 in zebrafish

Hsp47 is a major stress-inducible protein that is localized to the endoplasmic reticulum of avian and mammalian cells and is thought to act as a molecular chaperone specific for the processing of procollagen. Although hsp47 is coordinately expressed together with several collagen types, and vertebrate embryos are known to express collagen genes in complex spatial and temporal patterns, limited information is available regarding the function or regulation of hsp47 during early embryonic development. We have initiated an examination of hsp47 in the zebrafish, Danio rerio, which offers a number of features that make it attractive as a model developmental system with which to examine the expression and function of hsp47. A polymerase chain reaction (PCR)-based cloning strategy was used to isolate a hsp47 cDNA from an embryonic zebrafish cDNA library. The deduced translation product of the cDNA is a 404-amino-acid polypeptide that is 72% identical to chicken, 64% identical to mouse and rat, and 69% identical to human hsp47. The protein contains a typical hydrophobic signal sequence, an RDEL endoplasmic reticulum retention signal, and a serine protease inhibitor signature sequence, all of which are characteristic of hsp47 in higher vertebrates. Thus, it is likely that hsp47 in zebrafish is also localized to the endoplasmic reticulum and may play a similar role to its counterpart in higher vertebrates. Northern blot analysis revealed that the hsp47 gene is expressed at relatively low levels in embryos during normal development but is strongly induced following exposure to heat shock at the gastrula, midsomitogenesis, 2-day, and 3-day larval stages. The level of induction was much higher than has previously been reported in chicken and mouse cells.

Induction of a secondary embryonic axis in zebrafish occurs following the overexpression of beta-catenin

Formation of the vertebrate axis may involve a Wnt signaling cascade similar to the Drosophila wingless pathway. Zebrafish wnt8 is a candidate for involvement in axis specification insofar as it is expressed maternally and when overexpressed it can induce goosecoid, a transcription factor normally expressed in the embryonic shield. In this study we demonstrate that beta-catenin, a cadherin associated protein in the Wnt pathway, is expressed maternally in zebrafish and is widely distributed in the early embryo. Overexpressing beta-catenin in early zebrafish embryos induces goosecoid and ntl, ultimately leading to a duplication of a complete secondary axis. These data are consistent with the involvement of beta-catenin in a Wnt signaling pathway which is involved in mesoderm induction in zebrafish.

Wnt4 affects morphogenesis when misexpressed in the zebrafish embryo

The Wnts are a family of secreted glycoproteins involved in cell-cell signalling and pattern formation during development, although the extent to which various Wnts are functionally equivalent remains unclear. We have cloned zebrafish (Danio rerio) wnt4, characterized its expression, and compared its activity relative to other Wnts. The wnt4 transcript is first detected early in somitogenesis, in the dorsocaudal region of the forebrain, and then appears in the dorsal and lateral regions of the caudal hindbrain and neural keel. During somitogenesis, wnt4 appears in the floor plate, and this expression is absent in cyclops mutants, which lack floor plate. wnt4 is also expressed in the developing pronephros and gill slit. To characterize the biological activity of wnt4, synthetic zebrafish wnt4 mRNA was injected into embryos of zebrafish and Xenopus laevis. The phenotypic effects of misexpression in the zebrafish include cyclopia, misfolding in the brain, and an anteriorly forking notochord. Comparison of the phenotypes arising from misexpression of wnt4 and Xwnt-5A in both organisms suggests close parallels in the response to these Wnts. Our data suggest that wnt4, like Xwnt-5A, inhibits cell movements, and that these Wnts define a functional class distinct from the class which includes Wnt-1, Xwnt-3A and Xwnt-8.

Zebrafish wnt8 and wnt8b share a common activity but are involved in distinct developmental pathways

The specification of the vertebrate body plan is dependent on numerous signaling molecules, including members of the Wnt family. We have identified two zebrafish wnt8 paralogs related to Xwnt-8B and Xwnt-8, respectively. A RT-PCR assay demonstrated that wnt8 is expressed maternally, with transcripts detected throughout embryogenesis, whereas wnt8b transcripts were first detected during late gastrulation. The wnt8 transcripts at 50% epiboly are spatially restricted to those cells at the blastoderm margin, overlying gsc-expressing cells in the axial hypoblast. During late gastrulation, wnt8 was no longer detected in the marginal cells at the dorsal midline and by mid-segmentation, transcripts were found in the presumptive tail bud. In contrast, wnt8b expression is spatially restricted to prospective neuroepithelium, and later to neural-specific structures. Overexpression of both wnts results in two major phenotypes: radialized embryos and embryos with anterior defects. These phenotypes were preceded by significant changes in the spatial expression patterns of gsc and ntl transcripts, reminiscent of activities of Xwnt-8 in Xenopus, and consistent with a role for wnt8 in the specification or patterning of mesoderm.

The CNS-specific hyaluronan-binding protein BEHAB is expressed in ventricular zones coincident with gliogenesis

Hyaluronan (HA) is a ubiquitous component of extracellular matrices, and in several systems it plays a central role in regulating cellular proliferation and differentiation. Cell, or tissue,-specific functions of HA are likely to be mediated by cell, or tissue,-specific HA-binding proteins. We previously hyaluronan-binding protein from rat and cat (Jaworski et al., 1994). In view of the potential role of HA in neural differentiation, we examined the expression of BEHAB during late embryonic and early postnatal development of the rat. BEHAB is expressed at very high levels in ventricular zones throughout the neuraxis. Expression is first detected at embryonic day 15 (E15) in the spinal cord, and is detected at progressively more rostral levels at later ages. BEHAB expression, like other features of neural development, follows both caudal-to-rostral and ventral-to-dorsal gradients. The timing of BEHAB expression parallels the timing of the generation of glial cells. In all areas of the CNS examined, BEHAB expression begins after the peak of neurogenesis and coincident with gliogenesis. The regulation of proliferation and differentiation by HA in other tissues, together with the expression of BEHAB in zones of mitotic activity coincident with the generation of glia, suggests that the extracellular matrix protein encoded by BEHAB could play a role in the generation or differentiation of CNS glia.

Involvement of wnt1 and pax2 in the formation of the midbrain-hindbrain boundary in the zebrafish gastrula

The secreted signalling molecule encoded by the wnt1 gene and the paired box-containing pax2 gene are thought to play an integral role in patterning the zebrafish rostral nervous system. Using a double-label analysis, we compare the expression patterns of wnt1 RNA and pax2 protein during zebrafish embryogenesis to determine whether they were expressed in identical or overlapping patterns in individual embryos. During gastrulation, wnt1 RNA was detected in a pattern similar but not identical to the pax2 protein. Later, wnt1 and pax2 co-localize to the midbrain-hindbrain boundary. Exogenous retinoic acid, a teratogen that is known to affect the formation of the midbrain-hindbrain boundary, has a profound affect on both wnt1 and pax2 expression at gastrulation. Furthermore, when pax2 is overexpressed in zebrafish embryos, the wnt1 pattern of expression expands ventrally in the prospective rostral neuroepithelium. Despite the widespread and random distribution of exogenous pax2 RNA, it alone is unable to induce wnt1 expression in other ectopic sites. These results are consistent with the coordinate expression of wnt1 and pax2 being in a pathway responsible for establishing the midbrain-hindbrain boundary and support the earlier interpretation that pax2 may regulate wnt1 expression [Krauss et al., 1992], although only in a subset of embryonic cells. These data suggest that a predisposition for the regionalization of the central nervous system exists at gastrulation.

BEHAB, a new member of the proteoglycan tandem repeat family of hyaluronan-binding proteins that is restricted to the brain

Hyaluronan (HA) is a ubiquitous component of the extracellular matrix of all tissues. In the mammalian central nervous system (CNS) HA is present throughout development and into adulthood. While the functions of HA are likely to be mediated by HA-binding proteins, no cell or tissue specific HA-binding proteins have been reported. In an effort to characterize the composition of the extracellular matrix of the CNS, we sought to identify neural HA-binding proteins. We report here the isolation and characterization of a cDNA with a high degree of sequence homology to members of the proteoglycan tandem repeat (PTR) family of HA-binding proteins. Unlike other HA-binding proteins, the expression of this cDNA is restricted to the CNS. We propose the name BEHAB, Brain Enriched HyAluronan Binding protein, for this gene. The expression of BEHAB mRNA is developmentally regulated; expression is first detected in the late embryonic period and peaks during the first two postnatal weeks. In the embryo, BEHAB is expressed at highest levels in mitotically active cells. The sequence of BEHAB has long stretches of identity between rat and cat, suggesting that the encoded protein is functionally important. The size and sequence of BEHAB are consistent with the possibility that it could serve a function like link protein, stabilizing interactions between HA and brain proteoglycans. These observations suggest that existence of other tissue specific HA-binding proteins.

Expression of wnt10a in the central nervous system of developing zebrafish

A polymerase chain reaction-derived clone with sequence homology to partial-length shark and salamander Wnt-10a was used to screen a zebrafish cDNA library, yielding a cDNA encoding a full-length Wnt polypeptide. Transcripts encoding zebrafish wnt10a are first detected during the segmentation period of embryogenesis, at a time when there is extensive development and differentiation of the central nervous system. wnt10a transcripts are confined to differentiating brain regions, with expression first appearing diffusely in the floor of the hindbrain ventricle and proceeding anteriorly to the mid- and forebrain. Comparatively, zebrafish wnt1 transcripts are expressed in a stripe at the future midbrain-hindbrain boundary and at the future forebrain-midbrain border. With the differentiation of the neural tube into distinct regions, wnt1 signals are also detected along the dorsal midline of the midbrain, the mid- and posterior hindbrain, and the spinal cord. These patterns suggest roles for wnt10a in the regionalization of the brain.

The high molecular weight Cat-301 chondroitin sulfate proteoglycan from brain is related to the large aggregating proteoglycan from cartilage, aggrecan

Monoclonal antibodies Cat-301 and Cat-304 recognize a neuronal cell surface-associated chondroitin sulfate proteoglycan (CSPG), which is expressed during critical periods of postnatal development in the mammalian central nervous system (CNS). In the present study we show that the CNS CSPG identified by Cat-301/304 is similar to aggrecan, the high molecular weight CSPG from cartilage. By Western blot analysis, cartilaginous tissues, which are rich sources of aggrecan, have a high concentration of a high molecular weight CSPG which is immunoreactive with Cat-301 and 304. The Cat-301 and 304 epitopes, however, are partially masked by chondroitin sulfate glycosamino-glycan and are unmasked by digestion of the antigen with chondroitinase ABC. Although the antigen from both cartilage and CNS can be purified by CsCl buoyant density gradient centrifugation, a standard technique for purifying aggrecan, most of the antigen from the CNS has a lower buoyant density than that of cartilage. This may be due, in part, to the paucity of keratan sulfate substitution on the CNS antigen compared with that of the cartilage antigen. Both the CNS and cartilage antigens bind to hyaluronic acid, a feature characteristic of aggrecan. The physiochemical, biochemical, and functional properties of the Cat-301/304 antigen from cartilage are identical to aggrecan. The CNS antigen is similar, but not identical, to the cartilage antigen, and may thus represent another member of the family of high molecular weight CSPGs which bind to and aggregate with hyaluronic acid.

Identification of a calcium-dependent calmodulin-binding domain in Xenopus membrane skeleton protein 4.1

Xenopus membrane skeleton protein 4.1 is expressed constitutively during embryonic development and accumulates to high levels within the retina during normal morphogenesis. There exists a high degree of amino acid identity between Xenopus protein 4.1 and human protein 4.1, suggesting that the mechanisms known to modulate the function(s) of human protein 4.1 may also serve to regulate Xenopus protein 4.1. Calmodulin (CaM) is one regulatory protein known to affect membrane-cytoskeletal interactions. An in vitro binding assay was used to test the ability of Xenopus protein 4.1 to bind CaM. Two independent approaches, involving protein 4.1 synthesized in vitro from synthetic RNA or a partial length protein 4.1 fusion protein expressed in Escherichia coli, demonstrate calcium-dependent, CaM binding. Both approaches demonstrate that the CaM-binding site is within the amino-terminal region of Xenopus protein 4.1. Results of this calmodulin binding activity suggest a possible regulatory mechanism by which calcium and calmodulin may affect the function of protein 4.1 during development.

Membrane skeleton protein 4.1 in developing Xenopus: expression in postmitotic cells of the retina

Membrane skeleton protein 4.1 plays a key role in modulating the interactions of spectrin, actin, and integral membrane proteins in erythroid and nonerythroid cells. We have investigated its structure and expression during embryonic development of Xenopus laevis. An analysis of the complete 2758-nucleotide sequence and predicted translation of 801 amino acids (85.5 kDa) of X. laevis oocyte protein 4.1 reveals that, within overlapping regions, oocyte protein 4.1 is 74% identical to a composite amino acid sequence of human erythroid and lymphoid protein 4.1 and has an identity similar to that of amino acid motifs variably expressed in either human erythroid or lymphoid protein 4.1 S1 nuclease protection analysis demonstrates the presence of a single species of protein 4.1 transcript in embryos. Antibodies produced against X. laevis protein 4.1 fusion protein recognize two bands of 180 and 115 kDa on Western blots of X. laevis embryos and retina and, using immunocytochemical techniques, label the developing retina most intensely. In vitro transcription of a cDNA construct fully encoding X. laevis protein 4.1 yields a synthetic mRNA which, when translated in vitro, produces a polypeptide that comigrates on SDS-polyacrylamide gels with the 115-kDa form of embryos and retina. Protein 4.1 is found exclusively in photoreceptors following the terminal mitosis of retinal neurons. When retinal synaptogenesis is complete, protein 4.1 is also expressed in the inner retina. In adult amphibian retinas, protein 4.1 is detected in photoreceptors, bipolar cells, and ganglion cell axons. As these cell types have previously been shown to express spectrin, actin, and ankyrin, it is likely that the membrane skeleton of erythrocytes and retinal cells share functional similarities.

Reduction studies on bacterial recombinant somatomedin C/insulin-like growth factor-1

N-Met-Somatomedin C/insulin-like growth factor-1 (rSmC) had been produced in recombinant Escherichia coli in monomeric form. The intact rSmC peptide is initially synthesized in E. coli cells in denatured form as inclusion bodies. The rSmC peptide in these inclusion bodies was found in reduced form. Isolation of this rSmC peptide was accomplished by separation and dissolution of the inclusion bodies, with dissociation of non-covalently aggregated species. The reduced rSmC was converted to a metastable state, termed un-refolded rSmC. Further processing of this rSmC generated two other isomers, termed refolded rSmC. The transitions of the peptide among these different states, reduced rSmC, un-refolded rSmC, and refolded rSmC can be readily monitored by reversed-phase high-performance liquid chromatography. By reduction and re-oxidation of the purified individual isomers we found that they are likely to be related to each other as conformation isomers which appear to be stabilized by disulfide bonds.

Maternal ethanol consumption: binding of L-glutamate to synaptic membranes from whole brain, cortices, and cerebella of offspring

We examined the influence of chronic maternal ethanol consumption on the Na+- and Ca2+-independent binding of L-glutamate to synaptic plasma membranes from whole brain as well as from cortices and cerebella of developing offspring. The maximum specific binding (Bmax) of L-glutamate to the Na+- and Ca2+-independent binding sites in synaptic plasma membranes of brain peaked at 17 days of age in the offspring of both control and ethanol-fed rats, although at that age there were significantly fewer binding sites in the brains of the offspring of ethanol-fed rats. The regional localization of this deficit is not now known. However, it appears that one major glutamatergic region (the cortex) does not reflect the transient deficiency of L-glutamate sites in brain. In fact, the concentration of L-glutamate binding sites in cortical synaptic plasma membranes was significantly increased in the 20-day-old offspring of ethanol-fed rats. In contrast to the cortex, binding to cerebellar synaptic plasma membranes was comparable in 20-day-old offspring of control and ethanol-fed rats. Despite transient alterations in the concentrations of L-glutamate binding sites in brain and synaptic plasma membranes, the affinity of the sites for L-glutamate (Kd) was consistently normal in the 14- to 26-day-old offspring of ethanol-fed rats.

Gangliosides in axolemmal and synaptic membrane fractions from developing rats: effects of maternal ethanol consumption on offspring

Previous work from this laboratory has shown that in utero exposure to ethanol significantly alters the synthesis of glycoproteins in synaptic, axolemmal, and myelin membranes from developing rats. In an attempt to determine whether in utero exposure to ethanol similarly alters the synthesis of other glycoconjugates involved with cell-cell interactions, the present study examined the influence of chronic maternal ethanol consumption prior to parturition on the content and synthesis of gangliosides in axolemmal and synaptic plasma membranes from developing rats. The results demonstrate that, in contrast to central nervous system glycoproteins, synaptic and axolemmal glycolipids are minimally affected by in utero exposure to ethanol. At all ages examined (17 to 34 days of age), the offspring of control and ethanol-treated rats had a comparable distribution of radiolabel among synaptic and axolemmal gangliosides, a normal concentration of ganglioside sialic acid in synaptic plasma membranes, and a near-normal distribution of sialic acid among synaptic gangliosides. The present study provides evidence which indicates that the radiolabeling patterns of axolemmal and synaptic membrane gangliosides are similar. Specifically, the most heavily labeled synaptic and axolemmal gangliosides were GT1b (20-37% of the total radioactivity) and GD1a (20-32%). A smaller proportion of radioactivity was associated with GD1b (approximately 11-16%), GM1 (5-10%), and GQ1b (4-11%), as well as with GD3 and the other monosialogangliosides (less than 5%). During the age period examined the proportion of radioactive GT1b increased in both membrane fractions.

Maternal ethanol consumption: effect on (Na+-K+)-ATPase in rat offspring

The activity of Mg2+-activated, ouabain-sensitive adenosine triphosphatase, (Na+-K+)-ATPase, was determined in homogenates of hypothalamus, cortex, cerebellum, and brain stem from the 19-day-old offspring of rats that were pair-fed control or (6.6%, v/v) ethanol liquid diets on a chronic basis prior to parturition. In the offspring of both control and ethanol-fed rats the specific activity of (Na+-K+)-ATPase was significantly (p less than 0.01) greater in the cortex than it was in the hypothalamus, brain stem or cerebellum (hypothalamus approximately brain stem approximately cerebellum). When the offspring of ethanol-fed and control rats were compared we observed no significant (p greater than 0.05) differences in the activity of (Na+-K+)-ATPase in any of the four brain regions examined. In addition, the results of kinetic analyses of cortical (Na+-K+)-ATPase were similar in the 19-day-old offspring of ethanol-fed rats and those whose mothers consumed either the control liquid diet or standard laboratory chow. The results of these studies suggest that the activity of the plasma membrane enzyme, (Na+-K+)-ATPase, was not affected in the 19-day-old offspring of ethanol-fed rats.

Effects of [Na+], [Cl-], carbonic anhydrase, and intracellular pH on corneal endothelial bicarbonate transport

Sodium removal from the solution bathing the isolated rabbit corneal endothelium caused a reduction in both unidirectional and net flux of bicarbonate, whereas chloride withdrawal from the solution had no effect on the net bicarbonate flux but increased the unidirectional fluxes. These data correlate with previously published data on the effects of similar solution manipulations on both fluid movement and potential difference across the endothelium and strongly implicate bicarbonate as the primary ion involved in the maintenance of corneal hydration. Carbonic anhydrase (1 mg/ml) added to the solution bathing both sides of the endothelium markedly increased unidirectional and net bicarbonate fluxes, possibly by maintaining a high bicarbonate/CO2 concentration close to the membrane and thereby eliminating chemical gradients in the unstirred layer adjacent to the membrane. Determinations of intracellular pH with the 5,5-dimethyl-2,4-oxazolidine-dione method indicate that at more acid ambient conditions there is a lesser gradient between cell and bathing medium for H+; similar ambient conditions in other experiments resulted in larger unidirectional bicarbonate fluxes than at neutral pH. The data are suggestive of a nonvectorial H+-HCO3- exchange occurring across the endothelial cellular membranes.

Thermal Contrast in the Atmosphere of Venus: Initial Appraisal from Pioneer Venus Probe Data

The altitude profiles of temperature and pressure measured during the descent of the four Pioneer Venus probes show small contrast below the clouds but significant differences within the clouds at altitudes from 45 to 61 kilometers. At 60 kilometers, the probe which entered at 59.3 degrees north latitude sensed temperatures 25 K below those of the lower latitude probes, and a sizable difference persisted down to and slightly below the cloud base. It also sensed pressure below those of the other probes by as much as 49 millibars at a mean pressure of 200 millibars. The measured pressure differences are consistent with cyclostrophic balance of zonal winds ranging from 130 +/- 20 meters per second at 60 kilometers to 60 +/- 17 meters per second at 40 kilometers, with evidence in addition of a nonaxisymmetric component of the winds. The clouds were found to be 10 to 20 K warmer than the extended profiles of the lower atmosphere, and the middle cloud is convectively unstable. Both phenomena are attributed to the absorption of thermal radiation from below. Above the clouds, in the lower stratosphere, the lapse rate decreases abruptly to 3.5 K per kilometer, and a superimposed wave is evident. At 100 kilometers, the temperature is minimum, with a mean value of about 170 K.

Viking Lander Location and Spin Axis of Mars: Determination from Radio Tracking Data

Radio tracking data from the Viking lander have been used to determine the lander position and the orientation of the spin axis of Mars. The areocentric coordinates of the lander are 22.27 degrees N, 48.00 degrees W, and 3389.5 kilometers from the center of mass; the spin axis orientation, referred to Earth's mean equator and equinox of 1950.0, is 317.35 degrees right ascension and 52.71 degrees declination.