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Biomedical subjects

E Wallis

Publications and source records attributed to E Wallis.

8 recordsLinked to original sources
PubMed1995

Variations on a segmental theme: muscle receptor organs and extensor neuromusculature in the squat lobster Munida quadrispina (Anomura, Galatheidae)

Extensor neuromusculature and the muscle receptor organs (MROs) associated with them have been conserved during the evolution of malacostracan crustaceans, despite species-specific differences between homologous segments in divergent taxa. Investigations of these differences could provide insight into how sensory and neuromuscular elements are modified to accommodate changing behavioural patterns. The most obvious differences between squat lobsters (galatheid anomurans) and macruran decapods, such as crayfish, are the greater dorso-ventral flattening of the galatheid abdomen and its flexed resting posture. To investigate whether the evolution of this altered posture affected extensor neuromusculature and MRO morphology and physiology, we used Methylene Blue staining, cobalt backfilling and extracellular recording techniques to describe these elements in the caudal thoracic and six abdominal segments of the squat lobster Munida quadrispina and compared our results with published descriptions of homologous elements in macrurans. In M. quadrispina, there is segmental variation both in the orientation of the MROs along the abdomen and in their physiological responses to stretch: apparent sensitivity is higher in caudal than rostral MROs. Homologues of three of the four accessory neurones found in crayfish occur, but AN#1 has a major dendrite not present in crayfish. Intersegmental differences in size and morphology of extensor motoneurones occur in M. quadrispina, as have been reported in crayfish, but are dissimilar in the two: abdominal ganglion 5 extensor motoneurones are the largest in M. quadrispina and the smallest in crayfish; this difference correlates with the difference in relative size of axial muscles along the abdomen reported previously for these species. M. quadrispina also differs from macrurans in having a single tonic, and no phasic, MRO on each side of the last abdominal segment. Together, these observations suggest that galatheids have evolved modified or additional neurobehavioural control(s) for the abdomen and tailfan.

Journal Article↗
PubMed1992

[Differential diagnosis of fever after returning from the tropics].

Fever is the cardinal symptom of many infections in travellers returning from the tropics and is second in place only to infectious diarrhea. Once the obvious causes of fever in an individual patient have been eliminated, it may be very difficult to find the cause of fever. Fevers can be distinguished by their length of duration and divided into acute fevers i.e. up to 3 weeks duration and chronic fevers i.e. more than 3 weeks duration. Whether fever goes along with leucopenia or a normal white blood cell count on the one hand or with leucocytosis on the other hand is of differential diagnostic value. A schedule based on these two parameters will be presented to simplify differential diagnostic considerations. Two rules of thumb will be stressed: (1) Each febrile illness, even febrile diarrhea, jaundice or meningitis, is to be considered a malaria until it is excluded. (2) Patients returning from tropical areas might suffer from banal infections such as pneumonia, urinary tract infections, cholangitis, etc. as well.

Diagnosis, Differential↗
PubMed1992

[Management of patients with traveler's diarrhea].

Traveler's diarrhea starts 5 to 15 days after arrival with 3 or more watery bowel movements daily in 4 to more than 50% of travelers depending on geographical regions. Enterotoxin producing strains of E. coli are isolated in 20 to 50% of patients, followed by shigella, salmonella, campylobacter and vibrio spp. Rarely giardia lamblia, entamoeba histolytica and cryptosporidia are causative organisms. The cornerstone of treatment is oral rehydration. The efficacy of anti-diarrhetics is not convincingly proved and as to loperamid this drug may prolong invasive forms of diarrhea. Antibiotics are indicated if leucocytes or blood are found in stool. Cotrimoxazole and aminopenicillins are loosing efficacy because of growing resistance. The minimal. In a double blind placebo controlled trial with 500 mg ciprofloxacin b.i.d. for 5 days we were able to demonstrate a significant clinical and bacteriologic effect in 132 patients with salmonellosis and campylobacteriosis.

Anti-Bacterial Agents↗
PubMed1988

Selective breeding for increased cholinergic function: increased serotonergic sensitivity.

The effects of the serotonergic antagonist cyproheptadine and the agonist 1(m-chlorophenyl) piperazine (mCPP) on core body temperature, locomotor activity and operant responding for a water reward were determined in two lines of Sprague-Dawley rats selectively bred for differences in sensitivity to the anticholinesterase, diisopropyl fluorophosphate (DFP). Both cyproheptadine and mCPP induced a dose-dependent hypothermia that was significantly greater in the line of rat more sensitive to DFP (the Flinders Sensitive Line--FSL). On the other hand, the mild stimulant effects of cyproheptadine on operant responding and locomotor activity were similar in the two lines, whereas the marked inhibitory effects of mCPP on these two measures were significantly greater in the FSL rats. This study also confirmed that the FSL rats were significantly more sensitive to the hypothermic effects of oxotremorine, a muscarinic agonist, and showed that pretreatment with cyproheptadine reduced the hypothermic effects of oxotremorine to a similar extent in the two lines. These findings indicate that rats selectively bred for increased cholinergic function (FSL) also differ in their sensitivity to serotonergic agonists and antagonists, thereby extending the evidence for cholinergic-serotonergic interactions in the rat.

Animals↗
PubMed1984

Efficient expression of cloned complementary DNAs for secretory proteins after injection into Xenopus oocytes.

Cloned complementary DNAs encoding chicken ovalbumin, chicken prelysozyme and calf preprochymosin, prochymosin and chymosin were inserted downstream from various viral promoters in modified recombinant "shuttle" vectors. Microinjection of the ovalbumin, prelysozyme and preprochymosin constructs into the nuclei of Xenopus laevis oocytes resulted in the synthesis, segregation in membranes and secretion into the extracellular medium of ovalbumin, lysozyme and prochymosin, respectively. Judging from molecular weight estimations, lysozyme and prochymosin were correctly proteolytically processed while ovalbumin, which lacks a cleavable signal sequence, was glycosylated. Injection of the DNA construct encoding prochymosin without its signal sequence resulted in synthesis of prochymosin protein that was localized exclusively in the oocyte cytoplasm. No immunospecific protein was detected after injection of the DNA encoding mature chymosin. In terms of protein expression in oocytes, the Herpes simplex thymidine kinase (TK) promoter was up to sevenfold more effective than the simian virus 40 (SV40) early promoter, and equally as effective as the Moloney murine sarcoma virus long terminal repeat element. Where tested, protein expression in oocytes was much reduced if DNA sequences encoding the SV40 small t intron and its flanking sequences were present in the constructs. S1 nuclease mapping of transcripts produced after injection of DNAs containing the TK promoter indicated that the majority of transcripts initiated at, or within, two bases of the known "cap" site. However, minor transcripts initiating upstream from this site were observed and one (or more) of these transcripts was responsible for the synthesis of an ovalbumin polypeptide containing a 51 amino acid N-terminal extension. This extended protein remained in the oocyte cytosol. When ovalbumin cDNA was inserted into the vectors with opposite polarity to the viral promoter, expression in oocytes resulted in the predominant synthesis and secretion of a variant ovalbumin with a 21 amino acid N-terminal extension, although some full-length ovalbumin was also synthesized and secreted. S1 mapping revealed the presence, in these oocytes, of transcripts of predicted polarity initiating 118 bases upstream from the wild type ovalbumin initiator ATG, at a previously unreported SV40 "promoter". No protein synthesis was detected after the injection of these reverse-orientation constructs into baby hamster kidney (BHK-21) cells.

Amino Acid Sequence↗
PubMed1984

Segregation of mutant ovalbumins and ovalbumin-globin fusion proteins in Xenopus oocytes. Identification of an ovalbumin signal sequence.

The intramolecular signals for chicken ovalbumin secretion were examined by producing mutant proteins in Xenopus oocytes. An ovalbumin complementary DNA clone was manipulated in vitro, and constructs containing altered protein-coding sequences and either the simian virus 40 (SV40) early promoter or Herpes simplex thymidine kinase promoter, were microinjected into Xenopus laevis oocytes. The removal of the eight extreme N-terminal amino acids of ovalbumin had no effect on the segregation of ovalbumin with oocyte membranes nor on its secretion. A protein lacking amino acids 2 to 21 was sequestered in the endoplasmic reticulum but remained strongly associated with the oocyte membranes rather than being secreted. Removal of amino acids 231 to 279, a region previously reported to have membrane-insertion function, resulted in a protein that also entered the endoplasmic reticulum but was not secreted. Hybrid proteins containing at their N terminus amino acids 9 to 41 or 22 to 41 of ovalbumin fused to the complete chimpanzee alpha-globin polypeptide were also sequestered by oocyte membranes. We conclude that the ovalbumin "signal" sequence is internally located within amino acids 22 to 41, and we speculate that amino acids 9 to 21 could be important for the completion of ovalbumin translocation through membranes.

Amino Acid Sequence↗