Conformational changes in Sindbis virions resulting from exposure to low pH and interactions with cells suggest that cell penetration may occur at the cell surface in the absence of membrane fusion

Alphaviruses have the ability to induce cell-cell fusion after exposure to acid pH. This observation has served as an article of proof that these membrane-containing viruses infect cells by fusion of the virus membrane with a host cell membrane upon exposure to acid pH after incorporation into a cell endosome. We have investigated the requirements for the induction of virus-mediated, low pH-induced cell-cell fusion and cell-virus fusion. We have correlated the pH requirements for this process to structural changes they produce in the virus by electron cryo-microscopy. We found that exposure to acid pH was required to establish conditions for membrane fusion but that membrane fusion did not occur until return to neutral pH. Electron cryo-microscopy revealed dramatic changes in the structure of the virion as it was moved to acid pH and then returned to neutral pH. None of these treatments resulted in the disassembly of the virus protein icosahedral shell that is a requisite for the process of virus membrane-cell membrane fusion. The appearance of a prominent protruding structure upon exposure to acid pH and its disappearance upon return to neutral pH suggested that the production of a "pore"-like structure at the fivefold axis may facilitate cell penetration as has been proposed for polio (J. Virol. 74 (2000) 1342) and human rhino virus (Mol. Cell 10 (2002) 317). This transient structural change also provided an explanation for how membrane fusion occurs after return to neutral pH. Examination of virus-cell complexes at neutral pH supported the contention that infection occurs at the cell surface at neutral pH by the production of a virus structure that breaches the plasma membrane bilayer. These data suggest an alternative route of infection for Sindbis virus that occurs by a process that does not involve membrane fusion and does not require disassembly of the virus protein shell.     

Rapid intraoperative immunohistochemical evaluation of sentinel lymph nodes for metastatic breast carcinoma.

OBJECTIVE: Sentinel lymph node (SLN) biopsy is an integral part of the surgical management of patients with breast cancer. Rapid immunohistochemistry (RIHC) has the potential to increase detection of metastatic carcinoma at the time of frozen section consultation. The authors assessed the accuracy and turnaround time of a newly developed RIHC method for pancytokeratin (RIHC-CK). METHODS: Sixty-six SLNs from 32 patients with breast carcinoma were examined for metastasis using the Zymed Sentinel Lymph Node Rapid IHC Kit. Intraoperative frozen sections (6 mum) of the SLNs were incubated with Zymed anti-pan-cytokeratin/HRP conjugate, diaminobenzidine (DAB), and stained with hematoxylin. Slides were ready within 8 minutes and were interpreted as positive or negative for metastatic carcinoma. Results were compared with previous intraoperative touch preparations, frozen sections, hematoxylin and eosin (Perm H&E), and AEl/3-immunostained permanent sections (Perm CK). RESULTS: Fourteen lymph nodes (19%) in 13 patients tested positive for metastatic carcinoma in Perm H&E, the gold standard. RIHC-CK had the highest sensitivity (92%) of the intraoperative tests, compared with touch preparations (64%) and frozen sections (80%). RIHC-CK showed 94% accuracy, compared with 96% (frozen section) and 93% (touch preparation). The RIHC technique took 8 minutes and was easy to perform and interpret. CONCLUSIONS: Zymed RIHC is a sensitive method for detecting breast cancer metastases in SLNs. The speed, accuracy, and ease of interpretation of the test allow for recognition of micrometastases (<2 mm) that might otherwise be undetectable by current methods of intraoperative evaluation. The prognostic significance and effect on surgical management of micrometastases in SLNs have yet to be determined.     

Tizanidine (DS103-282), a centrally acting muscle relaxant, selectively depresses excitation of feline dorsal horn neurones to noxious peripheral stimuli by an action at alpha 2-adrenoceptors

The effects of microiontophoretic ejection of tizanidine were compared with those of adrenoceptor agonists on responses of single laminae IV and V neurones to noxious and innocuous cutaneous stimuli. Tizanidine, noradrenaline and clonidine depressed neuronal responses to noxious but not innocuous stimuli. Spontaneous activity was also depressed by these three substances. By contrast, beta- and alpha 1-adrenoceptor agonists had no consistent effect on neuronal responses to cutaneous stimuli. The selective actions of tizanidine, noradrenaline and clonidine were reversibly antagonized by the alpha 2-adrenoceptor antagonist RX781094 but not by WB4101 (alpha 1 antagonist). The binding of an alpha 2-adrenoceptor ligand to rat brain membranes was preferentially displaced by tizanidine. These results indicate an interaction of tizanidine with central alpha 2-adrenoceptors.     

Prediction of clinical course of bipolar manic depressive illness treated with lithium

A group of bipolar manic depressive patients attending a routine lithium clinic were investigated. The results suggest that, when on treatment with lithium, manic depressive patients with a good prognosis tend to have a higher erythrocyte Na-K ATPase and higher plasma and erythrocyte lithium concentrations than those with a poor prognosis. There was no evidence to suggest that the erythrocyte: plasma lithium ratio was useful in predicting clinical response to lithium therapy. There was also a positive correlation between plasma lithium concentration and Na-K ATPase activity, confirming that in manic depressive subjects lithium produces a rise in erythrocyte Na-K ATPase activity.     

Angiokeratoma corporis diffusum with features of a mucopolysaccharidosis.

Two cases of angiokeratoma corporis diffusum with mental retardation and some features of a mucopolysaccharidosis have been investigated biochemically, histopathologically, and by electron microscopy. It is submitted, on this evidence, that they are examples of a hitherto undescribed form of lysosomal enzyme deficiency disease.     

Using the demand–control model of job strain to predict caregiver burden and caregiver satisfaction in the informal caregivers of heart failure patients

Objectives The demand–control (D–C) model of job strain has generated a considerable body of empirical support in predicting psychological health outcomes in the context of work. This study aimed to extend previous work using the D–C model of job strain to predict caregiver burden and satisfaction in the informal caregivers of patients with heart failure. Design and method Data were gathered from 60 caregiver/patient dyads in a cross‐sectional design. Patients with chronic stable heart failure were recruited from out‐patient clinics. The dependent variables were caregiver burden and satisfaction. Demand and control were measured using both patient‐ and caregiver‐derived measures. Results The D–C model accounted for 15 and 19% of the variance in caregiver burden, after controlling for age, gender and relationship to the patient. Lower control was associated with higher burden. The D–C model did not predict caregiver satisfaction. Conclusion The D–C model was associated with caregiver burden, but not satisfaction in caregivers, with control being the dominant predictor. Research linking the theory and findings from job strain and informal caregiving studies may elucidate both fields of research. Using the demand–control model of job strain to predict caregiver burden and caregiver satisfaction in the informal caregivers of heart failure patients.     

Effects of potassium channel blockers on baclofen-induced suppression of paroxysmal discharges in rat neo-cortical slices

Baclofen reduced the frequency and aborted the bursts of spontaneous paroxysmal discharges in rat neocortical slices maintained in magnesium-free medium. This action was prevented by pretreatment with barium or caesium, which each increased the ictaform burst frequency, amplitude and duration. 4-Amino-pyridine also increased the burst frequency but reduced the amplitude and did not completely prevent the action of baclofen. Evidently baclofen suppresses such discharges by opening potassium channels normally involved in limiting the burst activity.