Intratympanic injection of sodium arsanilate (atoxyl) solution results in postural changes consistent with changes described for labyrinthectomized rats

Intratympanic injections of sodium arsanilate (atoxyl) have been shown to produce vestibular dysfunction in the rat. Unilateral and bilateral dysfunction can be distinguished by changes in the animals' postures. These changes are consistent with changes described for unilateral or bilateral labyrinthectomized rats. The intratympanic injection technique offers a simple yet effective alternative to labyrinthectomy.     

Clinical and pathological variability of infection by enterohaemorrhagic (Vero cytotoxin producing) Escherichia coli.

The clinical and pathological features of five sporadic cases of enteric infection caused by Escherichia coli O157 (enterohaemorrhagic or Vero cytotoxin-producing E coli showed a range of features. These included one case with pseudomembranous colitis, one with an acute exacerbation of ulcerative colitis, and three with enterocolitis. Diagnostic difficulties encountered initially in four of the five cases were finally resolved by correlating the results of microbiological with histopathological investigations. In view of the heterogeneity of clinical and histological signs and symptoms, it is concluded that all patients with abdominal pain and diarrhoea or rectal bleeding should have early microbiological investigation.     

Fluoride-resistant acid phosphatase-containing neurones in dorsal root ganglia are separate from those containing substance P or somatostatin

The distribution of fluoride-resistant acid phosphatase, substance P and somatostatin were investigated in the dorsal horn of the spinal cord and in dorsal root ganglia. In the dorsal horn, the distribution of fluoride-resistant acid phosphatase closely paralleled that of somatostatin and only partly overlapped with that of substance P. In sensory ganglia, none of the fluoride-resistant acid phosphatase-containing neurones contained either substance P or somatostatin. The results suggest the existence of a population of fluoride-resistant phosphatase-positive sensory neurones which is distinct from neurones containing either of these peptides.     

Clinical importance ofBilophila wadsworthia

Bilophila wadsworthia is an anaerobic, gram-negative, asaccharolytic, urease-positive, bile-resistant, catalase-positive bacillus, originally recovered from infections in patients with gangrenous and perforated appendicitis. Additional isolations from clinical specimens, including pleural fluid, joint fluid, blood and pus from a scrotal abscess, mandibular osteomyelitis and axillary hidradenitis suppurativa are described here.Bilophila is found as normal flora in feces and, occasionally, in saliva and in the vagina. Isolates from humans are usually -lactamase positive and therefore resistant to certain -lactam antibiotics. Two percent of strains are also resistant to clindamycin.     

Fertilization in vitro increases non-disjunction during early cleavage divisions in a mouse model system

BACKGROUND: We have been studying an unusual mouse-the BALB/cWt (Wt) male-in which the Y chromosome is susceptible to high rates of mitotic non-disjunction, particularly at the first two cleavage divisions. As these are the same divisions that human embryos generated through assisted reproductive technology must complete in an artificial setting, analysis of the Wt Y chromosome allows us to examine the effect of fertilization and culture in vitro on mammalian chromosome segregation. METHODS: We performed standard mouse IVF, cultured embryos in 5% CO2 in air or in a lowered oxygen atmosphere, and used fluorescence in-situ hybridization to examine the sex chromosome constitutions of 2-, 4-, 8- and 16-cell stage Wt Y-bearing embryos. RESULTS: We observed a significant increase in mosaic sex chromosome aneuploidy at each embryonic stage in embryos cultured in 5% CO2 in air, but under lowered oxygen conditions mosaicism returned to control (in-vivo) levels. CONCLUSIONS: Our results demonstrate that slight alterations in in-vitro conditions may have a considerable impact on the genetic quality of assisted reproductive technology-derived embryos and suggest that the genetic quality of embryos should be a fundamental concern in the development of new culture systems for clinical use.     

Reduction of ECS produced retrograde amnesia by post-trial introduction of strychnine

Strychnine sulfate was used to reduce the amount of retrograde amnesia induced by electroconvulsive shock (ECS). Male Swiss-Webster mice were trained on the step-down passive avoidance task, given ECS and then injected intraperitoneally with either 0.1 mg/kg strychnine or saline. The animals were tested in the apparatus one to twenty-four hours later. Mice given ECS alone displayed partial memory for the training (by responding with longer latencies) if tested within two hours after training, but did not display retention twenty-four hours later. Animals given strychnine following ECS had significantly longer step-down latencies at twenty-four hours than did the saline or no injection controls. Further experiments replicated the basic results, and also showed that strychnine injections delayed two hours after the training trial attenuated ECS-induced retrograde amnesia, but that a three hour injection delay was ineffective. The results were interpreted in terms of changes in short-term and long-term memory.     

Does the availability of either B cells or CD4+ cells limit germinal centre formation?

To determine whether the availability of either B cells or T cells regulates the number and size of germinal centres observed following antigenic challenge, irradiated PVG rats were reconstituted with limiting numbers of thoracic duct B cells (with excess T cells) or with limiting numbers of thoracic duct CD4+ cells (with sufficient B cells). Germinal centre formation was measured histologically in the spleens of reconstituted rats 7 days after immunization with 2 x 10(9) sheep erythrocytes (at the height of the germinal centre reaction). Although reconstitution with B cells and antigen alone, or with thymocytes and antigen alone, produced no germinal centres, saturating numbers of germinal centres on the order observed for normal, non-irradiated rats were observed in irradiated rats reconstituted with only 10(7) B cells and 5 x 10(6) CD4+ cells. Germinal centres in the spleens of minimally reconstituted rats were also comparable in size to those observed in normal rats. Reconstitution with either 4 x 10(7) thoracic duct lymphocytes (including 2 x 10(7) B cells, as well as CD8+ and CD4+ cells) or with 4 x 10(7) thoracic duct lymphocytes and 2 x 10(8) thymocytes also led to saturating numbers of germinal centres. It is concluded therefore that (i) CD4+ cells are sufficient for the T-cell contribution required for germinal centre formation, and (ii) some factor other than the availability of B cells or CD4+ cells normally limits germinal centre formation.     

Functional characterization of missense mutations at codon 838 in retinal guanylate cyclase correlates with disease severity in patients with autosomal dominant cone-rod dystrophy

Three different mutations in codon 838 of GUCY2D, the gene for retinal guanylate cyclase 1, have been linked to autosomal dominant cone-rod dystrophy at the CORD6 locus. To examine the relationship between enzyme activity and disease severity, the three disease-causing substitutions (R838C, R838H and R838S) and four artificial mutations (R838A, R838E, R838L and R838K) were generated. Assay of GCAP1-stimulated cyclase activity in vitro shows that, compared with wild-type, R838E, R838L and R838K possess only low activity, whereas R838A, R838C, R838H and R838S have activity equal or superior to wild-type at low Ca(2+) concentrations. These four latter mutants showed a higher apparent affinity for GCAP1 than did wild-type. The Ca(2+) sensitivity of the GCAP1 activation was also altered with marked residual activity at high Ca(2+), the effect increasing: wild-type < R838C < R838H < R838A < R838S. Within the photoreceptor, this would result in a failure to inactivate cyclase activity at high physiological Ca(2+ )concentrations. Amongst the three disease-associated mutations, the effect correlates directly with disease severity. The wild-type and R838H mutant displayed a difference in pH sensitivity, with the mutant showing a higher specific activity with pH > 6.0. Site 838 is in the dimerization domain that forms a coiled-coil in the active protein. A computer-aided structure prediction of this region indicates that R838 in the wild-type breaks the structure at four helical turns, and there is an increasing tendency for the structure to continue for further turns in the order R838C < R838H,S,K < R838E < R838A < R838L.