On the role of long incubation periods in the dynamics of acquired immunodeficiency syndrome (AIDS). Part 1: Single population models

In this study, we investigate systematically the role played by the reproductive number (the number of secondary infections generated by an infectious individual in a population of susceptibles) on single group populations models of the spread of HIV/AIDS. Our results for a single group model show that if R less than or equal to 1, the disease will die out, and strongly suggest that if R greater than 1 the disease will persist regardless of initial conditions. Our extensive (but incomplete) mathematical analysis and the numerical simulations of various research groups support the conclusion that the reproductive number R is a global bifurcation parameter. The bifurcation that takes place as R is varied is a transcritical bifurcation; in other words, when R crosses 1 there is a global transfer of stability from the infection-free state to the endemic equilibrium, and vice versa. These results do not depend on the distribution of times spent in the infectious categories (the survivorship functions). Furthermore, by keeping all the key statistics fixed, we can compare two extremes: exponential survivorship versus piecewise constant survivorship (individuals remain infectious for a fixed length of time). By choosing some realistic parameters we can see (at least in these cases) that the reproductive numbers corresponding to these two extreme cases do not differ significantly whenever the two distributions have the same mean. At any rate a formula is provided that allows us to estimate the role played by the survivorship function (and hence the incubation period) in the global dynamics of HIV. These results support the conclusion that single population models of this type are robust and hence are good building blocks for the construction of multiple group models. Our understanding of the dynamics of HIV in the context of mathematical models for multiple groups is critical to our understanding of the dynamics of HIV in a highly heterogeneous population.

Stimulus interaction between CO2 and almitrine in the cat carotid chemoreceptors

The hypothesis that augmentation of the carotid chemoreceptor response to hypoxia by almitrine is due in part to an increased response to CO2 was tested by using single or few fiber preparation of carotid body chemosensory fibers in 12 cats anesthetized with alpha-chloralose. To differentiate between the plausible mechanisms of effects, we also tested the responsiveness of the afferents to cyanide and nicotine before and after almitrine. After a saturation dose of almitrine (1 mg.kg-1 followed by 0.5 mg.kg-1.h-1) the chemosensory responses to CO2 strikingly increased even during hyperoxia: the afferents showing an increased transient peak activity at the onset of hypercapnia, an augmented steady-state response to CO2 stimulus, and a decreased arterial PCO2 stimulus threshold. Thus, the effect of almitrine on carotid chemoreceptor response to hypoxia could be explained, at least in part, by its multiplicative stimulus interaction with CO2. After almitrine, the chemoreceptor response to cyanide, which is dependent on arterial PO2, was not particularly augmented relative to those of nicotine. Accordingly, the O2-sensing mechanism does not appear to be the primary site of almitrine effect. The results also indicate that the site of CO2 chemoreception resides downstream from those of hypoxia.

Relationship between sympathetic and phrenic nerve responses to peripheral chemoreflex in the cat

To test the hypothesis that peripheral chemoreflex effect on the preganglionic cervical sympathetic nerve (PSN) activity is entirely mediated by the central respiratory drive (CRD), as expressed in the phrenic nerve (PN) activity, we studied the relationship between PN and PSN activities under controlled conditions of carotid chemosensory excitation in the anesthetized cats. The cats were vagotomized, paralyzed and artificially ventilated. Tracheal pO2 and pCO2, systemic blood pressure, activities of single or a few PSN and PN fibers and a PN bundle were simultaneously recorded. The PSN preparations, which were responsive to hypoxia and showed PN rhythm, were selected for the study. Carotid chemoreceptor excitation, produced by hypoxia (end-tidal pO2 approximately equal to 50 Torr) or by sodium cyanide injection (50-100 micrograms, i.v.), elicited 3 types of responses: (1) the PSN discharged during the silent period of PN activity, although the PSN peak activity was still coupled to the PN peak activity, (2) PSN discharged only during PN activity, and (3) during the absence of PN discharge induced by hyperventilation hypocapnia, cyanide injection stimulated the PSN without PN activity. These observations suggest a model of chemoreflex control of sympathetic nerve activity which consists of two parts: one is dependent on PN activity and the other is not. Accordingly, all PSN chemoreflex responses may not be integrated with all inspiratory chemoreflexes.

Multiple forms of growth inhibitors secreted from cultured rat liver cells: purification and characterization

It was found that a non-tumorigenic epithelial cell line from the liver of a Buffalo-strain rat (BRL) secreted into the culture medium various inhibitors of the growth of BRL and RSV-BRL (tumorigenic BRL transformed by infection of Rous sarcoma virus). The secreted inhibitors were classified into two types: one inhibited the growth of BRL to a greater extent than that of RSV-BRL (non-tumorigenic BRL growth inhibitor, NGI), and the other, vice versa (tumorigenic BRL growth inhibitor, TGI). Two NGI (NGI-I and NGI-II) and two TGI (TGI-I and TGI-II) were highly purified from the serum-free conditioned medium. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis without 2-mercaptoethanol, NGI-I and II gave protein bands with molecular weights (Mr) of 56,000 and 21,000, respectively. TGI-I and II gave a band that migrated faster than bromophenol blue marker dye, but they did not pass through an ultrafiltration membrane with an Mr cutoff of 5,000. In the presence of a reducing reagent, only NGI-II showed a decrease of Mr, from 21,000 to 11,000. NGI and TGI showed 50% growth inhibition with BRL and RSV-BRL, respectively, at 5-15 ng/ml in the medium containing 10% fetal calf serum. NGI and TGI all were stable to 1 M acetic acid (pH 2.3) and 6 M urea, but labile to 5 mM dithiothreitol or trypsin. Of the eight cell lines tested, NGI-I was most effective on BRL, NGI-II on BRL and HSC-3 (human tongue squamous carcinoma), and both TGI-I and II on RSV-BRL.

[Anisakids and human anisakiasis. 1. Bibliographic data]

Currently available data about larvae of Anisakidae (genera Anisakis, Pseudoterranova, Hysterothylacium and Contracaecum) from marine fishes are analysed. Hazard of such parasites for fish-consumers are emphasized.

Screening for schistosome eggs by digital image processing

Schistosomiasis is an epidemic disease that seriously endangers the health of people in China. Therefore, it is advantageous to screen for scFwistosome eggs automatically. This paper describes a screening method implemented on the Leitz TAS+ image analysis instrument for the presence of schistosome eggs in fecal samples.

Growth inhibitors in serum, platelets, and normal and malignant tissues

The non-malignant epithelial cell line from Buffalo rat liver (BRL) and its malignant transformant obtained by Rous sarcoma virus infection (RSV-BRL) were used as the indicators. A survey was made in animals for growth inhibitors which could inhibit the growth of BRL, but not the growth of RSV-BRL in culture, under the consideration that the loss of the sensitivity to such inhibitors might be the most dominant cause for acquisition of tumorigenicity. From human platelets, a growth inhibitor was extracted with acid-ethanol and prepared to a homogeneous purity, separated from the major TGF-beta activity, which stimulated the anchorage-independent growth of NRK cells in the presence of EGF. The purified inhibitor (Mr 25-27k; pI 8.7-9.1) showed 50% inhibition on the growth of BRL at 20 pg/ml (0.7 pM), but hardly influenced the growth of RSV-BRL. Its inhibition was specific to epithelial cell lines, thus called epithelial growth inhibitor (EGI). It consisted of two subunits with practically identical Mr, which were cross-linked with disulfide bonds. Its sequence of N-terminal 10 amino acids was consistent with that of TGF-beta. In rats, serum contained a growth inhibitor with Mm 220k. The inhibitor, when treated with high concentrations of urea or guanidine-HCl, liberated an active component with Mr 30k and pI 5.2. When the growth inhibitor with Mm 220k was treated with ethanol-acetone or 1 M acetic acid, its activity increased more than 10-fold. Growth inhibitors were extracted with acid-ethanol from various tissues of rats. The activities of the extracts to inhibit the growth of BRL cells were high in spleen, lung and tumors with relatively high mitotic activities, but low in muscle, heart and brain. Acid-ethanol extract from BRL cells showed growth inhibitory activity toward BRL cells themselves significantly higher than that from RSV-BRL cells. The serum-free media conditioned with BRL and RSV-BRL cells showed a little growth inhibitory activity toward BRL cells. On treatment with acetic acid, their activities increased significantly, comparable for both types of cells. The media thus activated inhibited the growth of BRL cells, but not that of RSV-BRL cells. All the growth inhibitors described above including human platelet inhibitor, whether present in extracts or purified, resembled one another in stability against acid, heat and reducing reagents.

Purification and properties of epithelial growth inhibitor (EGI) from human platelets: its separation from type beta transforming growth factor (TGF-beta)

We previously reported that sera from various kinds of animals contain a protein(s) capable of inhibiting the growth of the non-malignant epithelial cell line derived from Buffalo rat liver (BRL). In the present study, a similar epithelial cell-specific growth inhibitor (EGI) was purified to homogeneity from an acid-ethanol extract of human platelets. During purification, EGI was separated from the major component of type beta transforming growth factor (TGF-beta), which can stimulate the colony formation of the non-malignant fibroblastic cell line derived from rat kidney (NRK) in soft agar in the presence of epidermal growth factor (EGF). The purified EGI had an Mr of 27,000, and was composed of two subunits identical in Mr. It significantly inhibited the growth in monolayer cultures of three non-malignant epithelial cell lines, BRL, MDCK (from Madin-Darby canine kidney) and BSC-1 (from African green monkey kidney), at doses lower than 40 pg/ml in medium containing 10% fetal calf serum. Its inhibitory activity was stable against heating at 90 degrees C for 3 min, but not against treatment with 50 mM dithiothreitol. In addition, TGF-beta was also partially purified from the same extract. The purified TGF-beta did not show any inhibitory activity toward the growth of BRL, MDCK, BSC-1, or NRK.

Proteoglycans in human atherosclerotic lesions--a pilot qualitative and quantitative study by ruthenium red

A pilot study was carried out to test whether normal human aorta and aortic atherosclerotic lesions obtained at post-mortem examination were suitable for the demonstration of proteoglycans (PGs) by ruthenium red (RR) staining, and whether by this method qualitative and quantitative differences of PGs might be detectable in various types of lesions and between lesions and the normal aortic intima. The results indicate that the PGs of the above tissues obtained at post mortem were clearly visualized by electron microscopy using the RR-indicator and were thus suitable for quantitative and qualitative evaluation. Of the RR-positive granules only those 20 nm and larger were assessed. RR-granules measuring 20-50 nm were present in normal intima and media, in increased concentration in the innermost part of the mixed fatty-gelatinous lesion, and in a decreased concentration in the fibrous cap of an atherosclerotic plaque. The same RR-granules were observed in a fatty streak and in addition 50-100 nm granules were present in this type of lesion; the overall RR-granule-concentration was reduced here. Granules of both sizes were interconnected by filamentous network. The differential presence of the large (and hitherto unreported) as well as the smaller granules in the various lesions is briefly discussed in the light of the present-day knowledge of tissue-PGs, and the importance of an examination in situ of the compound PGs-complexes in their native form, is emphasized.

Proteoglycan distribution in rat aortic wall following indwelling catheter injury

The morphologic response of the aortic wall of the normal fed rat to intimal injury by an indwelling catheter in place for 3 weeks was examined at the time of removal of the catheter and 4, 8, and 26 weeks later. Changes in the concentration of glycosaminoglycan were assayed morphometrically in ruthenium red-stained sections examined by transmission electron microscopy. Two types of ruthenium red-positive granules were identified in the intercellular matrix; large (greater than 20 nm), containing chondroitin sulphate and small (less than 20 nm) containing heparan sulphate. Endothelial denudation and some thrombus seen at the time of removal of the catheter, was associated with a decrease in the concentrations of both types of granules in the subendothelial space compared to normal rats. At later time intervals there was neointimal thickening containing no lipid, and occasional small areas of lipid accumulation. Compared to normal rats there was no significant change in granule concentration in the subendothelial space at any time interval. There was a slight increase in the concentration of large granules of the deep neointima at the time of removal of the catheter and after 4 weeks. In lipid-containing areas there was a highly significant increase in large granule concentrations compared to normal or to intimal thickening without lipid. The observations support the possibility that lipid accumulation is related to an increase in glycosaminoglycan concentration.

Peptide immunoreactive nerves and cells of the guinea pig gall bladder and biliary pathways

Using the methods of immunocytochemistry and radioimmunoassay, five peptides (vasoactive intestinal polypeptide (VIP), substance P, somatostatin, met-enkephalin, and bombesin) have been found in the gall bladder and the biliary tracts of guinea pig and each of them possesses a characteristic distribution pattern. Networks of nerves containing each peptide were found in the smooth muscle, around blood vessels and, occasionally, in the lamina propria. The distribution of the peptide immunoreactive nerves in the gall bladder and biliary tract is similar to those found in the gut. Vasoactive intestinal polypeptide (11 +/- 1.5 pmol/g in the sphincters, mean +/- SEM) and substance P (21.5 +/- 1.8 pmol/g in the common bile duct) were found to be the most abundant peptides and a few VIP and substance P immunoreactive neurones were localised in the ganglionated plexus. Bombesin immunoreactive nerves were mainly seen in the sphincter of Oddi, where the mean concentration of extractable bombesin was 14.6 +/- 2 pmol/g. Somatostatin immunoreactive mucosal endocrine cells were identified in the epithelium of the common bile duct and the sphincter. The extractable somatostatin in these regions were 76 +/- 19 pmol/g and 162 +/- 30 pmol/g respectively.

[Comparative double-blind study of cefotetan and cefmetazole in patients with purulent peritonitis]

A clinical study of daily administrations of CTT (2g) and CMZ (4g) was performed by randomized double blind techniques in order to compare the clinical efficacy, side effects and usefulness. The 150 cases studied were as follows; Purulent peritonitis due to perforated gastrointestinal tracts (122 cases), traumatic peritonitis (4 cases), biliary peritonitis (7 cases), postoperative peritonitis (7 cases), intraabdominal abscess (6 cases); 4 cases were excluded from the statistical evaluation because of protocol deviation. 1. No significant differences in background parameters were found between the 2 groups. 2. Clinical evaluation of the efficacy rate by the attending physician revealed no significant differences between the 2 groups (CTT 82%, CMZ 74%). However, in severely perforated duodenal and/or gastric ulcer cases, greater clinical effectiveness was obtained in the CTT group than in the CMZ group (P less than 0.05). 3. Clinical evaluation of the efficacy rate by the committee revealed no significant differences between the 2 groups; 86% and 82% for the CTT and CMZ groups, respectively. However, in cases which showed marked effectiveness, although statistical significant differences were not found between the 2 groups (P less than 0.1), the CTT group (53%) was superior to the CMZ group (38%). In 122 cases of the purulent peritonitis, the efficacy rate was 92% in the CTT group and 86% in the CMZ group; this difference was also statistically significant by U-test (P less than 0.05). 4. The effectiveness was also evaluated by microbiological study in 90 cases. No significant differences were found in the ratio of eradication of isolated bacteria between the 2 groups; 30 of 44 cases (68%) in the CTT group and 34 of 46 cases (74%) in the CMZ group. 5. With regards to this eradication of bacterial strains; 115 of 119 strains (96.6%) were eradicated in the CTT group and 115 of 126 strains (91.3%) in the CMZ group. 6. Side-effects were noted in 2 cases in the CTT group; one case of nausea with chest discomfort and the other case of drug eruption. In the CMZ group, only 1 case of drug eruption was noted. Moreover, no significant differences were found in the laboratory findings between the 2 groups. Based on these results it was concluded that the clinical effectiveness of CTT (1 g twice daily) against peritonitis is as excellent as that of CMZ (2 g twice daily), both drugs being administered by drip infusion.

The management of cardiovascular complications in elderly patients with coronary heart disease subjected to major surgical operations

There was not a single cardiovascular mortality in 140 consecutive elderly patients with coronary heart disease who were subjected to major surgical operations. The age distribution, the varieties of coronary heart diseases, and surgical operations were listed. the preoperative preparation, management during and after the operations were presented. In the discussion (1), the well-coordinated teamwork among the physicians, surgeons, anesthetists, and nursing staff before, during, and after the operations was stressed. (2) The managements of various cardiovascular complications were discussed in detail. Illustrative case materials were presented whenever necessary.

Re-evaluation of the relationship between the positive inotropic effect of ouabain and its inhibitory effect on (Na+ + K+)-dependent adenosine triphosphatase in rabbit and dog hearts

Previous studies have shown that in the ouabain-exposed rabbit heart, although positive inotropy and inhibition of (Na+ + K+)-dependent adenosine triphosphatase are induced concomitantly, the extent of inhibition of the enzyme remains constant when positive inotropy is washed out; and in the dog heart, if positive inotropy without arrhythmias is induced by ouabain, inhibition of the enzyme is not detected. The purpose of this work was the re-evaluation of these previous findings. Rapid recovery of the enzyme from small tissue samples was achieved by homogenization in 1 M KCl and centrifugation. When the enzyme was prepared by this method from ouabain-exposed rabbit and dog hearts, ouabain remained bound to the enzyme. The extent of inhibition of the enzyme was measured by the fluorimetric assay of K+-dependent 3-O-methylfluorescein phosphatase before and after removal of bound ouabain. Correlation between the extent of inhibition of this activity and that of (Na+ + K+)-dependent adenosine triphosphatase activity was established. Utilizing these refined methods, the following results were obtained. In the rabbit heart, positive inotropy and enzyme inhibition occurred concomitantly. Washout of the effect resulted in partial reactivation of the enzyme. In the dog heart, the previous findings were confirmed. The results are not inconsistent with the hypothesis that enzyme inhibition is the cause of the positive inotropic effects. They do suggest, however, the need for further testing of the hypothesis.