Molecular analysis of the virulence locus of the Salmonella dublin plasmid pSDL2

The virulence properties of various non-typhoid Salmonella serotypes depend on the presence of large plasmids 60-100 kb in size. We have shown previously that the virulence region on the 80 kb plasmid pSDL2 of Salmonella dublin Lane maps within a 14kb SalI fragment. In this report we show that an 8.2 kb region within this fragment is sufficient to express lethal disease in BALB/c mice. Sequence analysis of this segment revealed six sequential open reading frames designated vsdA-F, which encode putative proteins of 13-65kDa. Deletion analysis and location of Tn5-oriT inserts which abolish virulence suggest that vsdA, vsdC, vsdD and vsdE are essential for virulence expression. Downstream of vsdF we discovered a locus involved in stable plasmid maintenance. Deletion of that region resulted in plasmid multimerization and instability.

Selection of Cells Defective in Pyrimidine (TK(-)) and Purine (APRT (-) and HPRT (-) Salvage : Development of Host Strains Appropriate for Transfection

The usefulness of the purine and pyrimidine salvage pathways in the study of the mechanisms of mutation and in the selection of cell lines stably transformed by vectors expressing these genes is well documented. Unfortunately, many investigators are deterred from selecting new host strains deficient in these enzymes because of the difficulties inherent in isolating recessive mutations of autosomal genes. Furthermore, considerable suspicion was cast over somatic cell genetics by the so-called epigenetic nature of some phenotypic changes (1). However, given the clear molecular basis of the vast majority of mutant phenotypes, such apprehensions are largely unwarranted, provided that careful, clean selections are employed (e.g., see. 2).

Isolation and expression of the gene for a major surface protein of Giardia lamblia

To study the interactions between the parasitic protozoan Giardia lamblia and its environment, we have cloned the gene that encodes the two major surface-labeled trophozoite protein species. Sequence analysis of this gene reveals a single open reading frame specifying a hydrophilic, cysteine-rich (11.8%) protein of 72.5-kDa molecular mass with an amino-terminal signal peptide and a postulated hydrophobic membrane-spanning anchor region near the carboxyl terminus. Most of the cysteine residues (58 of 84) are in the motif Cys-Xaa-Xaa-Cys, which is dispersed 29 times throughout the sequence. Antibodies against the recombinant protein react with the entire surface of live trophozoites, including flagella and adhesive disc. These antibodies inhibit trophozoite attachment, prevent growth, and immunoprecipitate the major approximately 66- and 85-kDa proteins from surface-labeled live trophozoites. The recombinant Escherichia coli also expresses polypeptides of approximately 66- and 85-kDa molecular mass, which are not fusion proteins. This suggests that the processing and/or conformational changes that lead to production of these two peptide species in E. coli reflect those that occur in Giardia. The abundance of cysteine residues suggests that the native proteins on the parasite surface may contain numerous disulfide bonds, which would promote resistance to intestinal fluid proteases and to the detergent activity of bile salts and would help to explain the survival of Giardia in the human small intestine.

Does the dexamethasone suppression test predict antidepressant treatment success?

The 1 mg dexamethasone suppression test (DST) was carried out in patients with a major depressive illness in order to establish whether the results of this test, given before antidepressant or ECT treatment, could predict eventual therapeutic outcome. No significant difference could be detected in overall therapeutic improvement between those patients with a normal or abnormal DST response respectively, based on the 50 ng/ml cortisol cut-off point. However, using 100 ng/ml as a cut-off point it was found that patients with an abnormal DST response (i.e. a post-DST plasma cortisol concentration greater than or equal to 100 ng/ml) responded significantly better than those who had a normal DST response. These observations were statistically significant for those patients receiving antidepressants and in the combined treatment groups of those patients receiving either antidepressants or ECT.

Platelet accumulation of histamine in controls, depressed and lithium-treated patients

The accumulation of histamine into blood platelets of depressed patients, lithium-treated patients and controls was determined using radio-labelled histamine. All groups had significantly different mean accumulation rates: the depressives had the lowest, the controls had the highest while the lithium-treated patients had intermediate rates. No significant difference in histamine accumulation rates was detected between drug-free depressed patients or depressed patients receiving psychotropic medication apart from lithium. Histamine accumulation rates of depressed patients did not appear to have been influenced by their age or severity or endogenicity of their illness; no difference in histamine accumulation was detected between those patients who had an abnormal or normal dexamethasone suppression test response. We have concluded that while the biological significance of these results is unclear it would appear to be a very sensitive test for depression, especially in women. It would appear that prophylactic lithium treatment increased the rate of histamine accumulation: this result is discussed with reference to histamine's association with allergic disorders.

Depression, weight loss and the dexamethasone suppression test

The dexamethasone suppression test (DST) was carried out on 143 patients with a major depressive disorder, who were classified into those with a history of weight loss (n = 89) and those without (n = 54). Seventy-three per cent of patients with weight loss and 61% of patients without had an abnormal DST; this difference was not statistically significant. Of the patients receiving prophylactic lithium therapy, 13 were found to have changed their DST status on retesting after a period of 14 months, but there was no significant difference in their weight. It is concluded that weight loss is not a necessary condition for an abnormal DST in depressive illness.

Dexamethasone suppression test in depression and other psychiatric illness

The prevalence of an abnormal response to the dexamethasone suppression test (DST) was examined in 119 in-patients suffering from a major depressive disorder and in 79 normal controls. Only 11 per cent of controls showed an abnormal DST as against 70 per cent of depressed patients. The specificity of the DST was examined by testing patients with other psychiatric disorders. Abnormal responses were found in one-fifth of a sample of schizophrenics, over one-quarter of abstinent alcoholics, two-fifths of neurotics (including neurotic depressives) and almost half of senile dements. Abnormal DST was also found in 33 per cent of patients receiving prophylactic lithium for recurrent affective disorders.

The effect of antidepressant drugs on plasma kynurenine in depressed patients

The concentration of kynurenine in plasma from depressed patients and control subjects has been measured using a sensitive and specific method. The levels of kynurenine in the plasma of depressed patients and controls are not significantly different and are not influenced by age or sex. The severity of affective disturbance was not related to plasma kynurenine levels in depressed patients. Clinical outcome could not be accurately predicted by measurement of plasma kynurenine levels. Amitriptyline did not significantly increase plasma kynurenine concentration in vivo, whereas lithium and mianserin did have a significant effect. These results are discussed with reference to known abnormalities of tryptophan metabolism in depressive illness and in particular to the 5-hydroxytryptamine uptake characteristics of blood platelets in depressive patients.

Decreased tryptophan excretion by depressive patients

The concentration and 24-h urinary excretion of tryptophan has been measured in urine samples from monopolar female depressed patients and female control subjects. Female depressed patients and the control subjects excrete similar amounts of tryptophan. Patients with endogenous features of depression excrete significantly less tryptophan in 24 h than do the patients with reactive features and the control subjects. The relationship between plasma tryptophan concentration and 24-h urine tryptophan excretion in control subjects has been investigated and the results discussed in the light of abnormalities of tryptophan metabolism in depressive illness.

Significance of lymph node metastasis in differentiated thyroid cancer

In age-matched patients with differentiated carcinoma of the thyroid, the tumor recurred in 32 per cent of those with lymph node metastases and in 14 per cent of those without lymph node metastases. Twenty-four per cent of patients with nodal involvement at the initial examination died of thyroid cancer, whereas only 8 per cent of those without nodal involvement died of thyroid cancer. In patients less than forty years old, there were no deaths in those without nodal metastases bu there were three deaths (11 per cent) in patients with nodal metastases. In patients more than forty years old, nine (41 per cent) iwth nodal metastases died of tumor, and four (15 per cent) without nodal metastases died of tumor. In the presence of positive nodes the death rate was substantially greater in the older than in the younger patients. Nodal involvement has an adverse effect on prognosis, but appears to be less important than the age of the patient.

Comparison of methods for the determination of total and free tryptophan in plasma

A comparison is made between two fluorimetric techniques for the determination of total and free plasma tryptophan. Comparison is also made between methods for the separation of the unbound and bound fraction of plasma tryptophan using ultrafiltration, Centricones and small-scale equilibrium dialysis.

The effects of inhaled silica and chrysotile on the elastic properties of rat lungs; physiological, physical and biochemical studies of lung surfactant

When rats breathed air containing approximately 70 mg m-3 of respirable crystalline silica 7 h daily for 10 days (2000 mg m-3 h) the surface tension forces of the alveolar lining film were reduced. This was shown both by surface tension measurements on lung extracts and by pressure-volume studies with air and saline filling of excised lungs. Larger quantities of inhaled silica produced similar effects. Chrysotile inhalation caused an even more marked decrease in the surface tension forces. In the chrysotile studies these findings were supported by biochemical estimations of the quantity of surfactant in the lungs, which was increased 10-fold by an inhalation of 6500 mg m-3 h. Electron microscopy showed an increased number of the type II alveolar cells which produce surfactant and of free phospholipid lattices in the air spaces of the lungs of rats exposed to chrysotile and silica. Both the surface tension and biochemical estimations on a control group of rats suggest that there is an increase in the amount of surfactant in the lungs up to about 12 months of age.

Right Hemihypertrophy and Pubertas Præcox

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II. A letter from Dr John Harwood, LL. D. and F. R. S. to Dr Hans Sloane, R. S. Secr, concerning the forementioned Hypocaustum. With part of two letters from Mr William Baxter to Dr Harwood, relating to Wroxeter, and the Hypocausta of the ancients

Sir , The first notice I had of the Hypocaust discover’d at Wroxeter , was from a Letter Mr Baxter communicated to me, which he received from the Reverend Mr Markham , the present worthy Incumbent of that place; which gave me occasion of making farther enquiry, by writing to the Reverend Mr Richard Lloyd of Salop ; who, at my request, was so obliging as to take a journey and view it.