Parasites and supernormal manipulation.

Social parasites may exploit their hosts by mimicking other organisms that the hosts normally benefit from investing in or responding to in some other way. Some parasites exaggerate key characters of the organisms they mimic, possibly in order to increase the response from the hosts. The huge gape and extreme begging intensity of the parasitic common cuckoo chick (Cuculus canorus) may be an example. In this paper, the evolutionary stability of manipulating hosts through exaggerated signals is analysed using game theory. Our model indicates that a parasite's signal intensity must be below a certain threshold in order to ensure acceptance and that this threshold depends directly on the rate of parasitism. The only evolutionarily stable strategy (ESS) combination is when hosts accept all signallers and parasites signal at their optimal signal intensity, which must be below the threshold. Supernormal manipulation by parasites is only evolutionarily stable under sufficiently low rates of parasitism. If the conditions for the ESS combination are not satisfied, rejector hosts can invade using signal intensity as a cue for identifying parasites. These qualitative predictions are discussed with respect to empirical evidence from parasitic mimicry systems that have been suggested to involve supernormal signalling, including evicting avian brood parasites and insect-mimicking Ophrys orchids.     

Etiology of influenza according to the data of serological diagnostics in hospital patients in St. Petersburg at the period of 1968 - 2000

The specific features of the etiology of influenza in children and adults at the period of the simultaneous circulation of two subtypes of influenza virus A, according to the results in the hemagglutination-inhibition reaction in 261,490 influenza and ARD patients hospitalized in St. Petersburg in the course of 32 years, were analyzed. The results of serological diagnostics was shown to correspond to the data of the identification of influenza viruses in Russia and all over the world. At the period of epidemics diseases caused by the main infective agents of the epidemics were detected in 11.0% - 51.0% of cases and by concomitant infective agents, in 0.6% - 12.4% of cases. After the reappearance of influenza virus A(H1N1) in circulation higher frequency of mixed forms of infection and the presence of competition between the subtypes of influenza virus A was noted. In young children a decrease in differences in the proportion of influenza cases, caused by the main and concomitant infective agents, as well as between the detection of influenza in epidemic and in summer periods, was registered.     

Etiology of shock in blunt trauma.

Patients who have suffered blunt trauma and present in shock of uncertain cause represent a problem frequently encountered by emergency physicians. A retrospective review of the charts of 879 patients who had suffered blunt trauma and presented to a regional trauma unit over a 44-month period revealed that 154 of the patients had presented to either a hospital or the trauma unit in shock. The most common causes of shock when a single source of hemorrhage was identified were, in order of decreasing frequency, intraperitoneal hemorrhage, pelvic or other musculoskeletal fractures, thoracic hemorrhage, severe head injury and spinal cord injury. Severe head injuries accounted for only 8% of the single-source cases and contributed to shock in only seven of the remaining cases.     

Compartmentalizing the S period.

In order to increase the resolution of interphase analysis we have developed a method which is an alternative to cytofluometric techniques for tissues where cell flow is not applicable. The method combines the estimation of cell frequency in G1, S, G2 and mitosis after a 3H-thymidine pulse with the grouping of interphase cells according to their DNA content, as estimated by cytophotometry in Feulgen stained nuclei. By superimposing both sets of data we get three different artificial compartments within the S period. As a biological test of the resolution reached, the method readily confirmed that hydroxyurea, after one cycle time, accumulates cycling cells of Allium cepa L. root meristems in early S.     

Etiology of breast cancer. II. Epidemiologic aspects

The epidemiology of breast cancer is reviewed with particular emphasis on its etiology. A number of studies suggest that differences in breast cancer incidence are associated with differences in marital status, number of pregnancies, age at menarche, age at menopause, height and weight, socioeconomic status, geographic location and residence. However, in no case is the evidence adequate to establish a “cause and effect” relationship. The genetic component of these associations may be of primary importance, while other conditions such as marital status are probably indirect reflections of the operation of more fundamental factors.There is a general consensus that endocrine factors play an important part in mammary cancer occurrence. At present, the association between breast cancer and the presence of the virus-like (type B) particles in human milk is not established.     

On the Etiology of Sarcoidosis

Bacteriophages lytic for tubercle bacilli were isolated from tuberculous patients and patients with sarcoidosis. While tuberculous patients were found to raise phage-neutralizing antibodies, those with sarcoidosis appeared unable to do so. In vitro experiments showed that in the absence of neutralizing antibodies, phagolysis and lysogenic conversion of tubercle bacilli proceed. Lysogenic conversion results in the emergence of bacilli so modified in their morphological and antigenic properties that, on the basis of the classical bacteriological criteria, they can no longer be recognized as tubercle bacilli. From six lymph node biopsies collected from patients with sarcoidosis and cultured on a variety of media, including media containing anti-phage sera, five variant strains of tubercle bacilli were isolated. These observations support the view that certain cases of sarcoidosis are due to “modified” tubercle bacilli.     

Etiology of breast cancer I. Genetic aspects

The subject of breast cancer is reviewed with particular emphasis on the genetic aspect of its etiology. A number of studies using various approaches gave the same results: the familial form occurs earlier and there is a higher risk in female members of the breast-cancer families. An association between breast cancer and cancer of certain other sites among women is reported. Cytogenetic studies of “cancer families” revealed increased frequency of aneuploidy in some members. However, the role of chromosome abnormalities in carcinogenesis is still not clear.     

Pulmonary renal syndromes. II. Etiology and pathogenesis.

Numerous systemic diseases share immunopathogenic mechanisms. This article reviews the proposed etiologies and immunopathogenic mechanisms of a group of diseases which share pulmonary and renal abnormalities. Specifically, we discuss the following diseases: Good-pasture''s syndrome, systemic lupus erythematosus, progressive systemic sclerosis, Wegener''s granulomatosis, lymphomatoid granulomatosis, and Churg-Strauss syndrome.     

Androstenedione therapy reinstates normal, not supernormal, song structure in castrated adult male zebra finches.

In previous studies, androstenedione (AE) replacement therapy restored the highest levels and intensities of courtship song displays in castrated male zebra finches of any hormone tested. Furthermore, female zebra finches responded strongly to AE-treated males and preferred intact males given small AE implants to unsupplemented males. In this study, we asked whether AE treatment might alter song structure, since male song is an important cue in mate choice by female zebra finches. Songs of adult males were recorded. The males were then castrated and given AE therapy and recorded again. No differences were found between the courtship or undirected songs males sang before castration and after AE treatment. As in previous studies, the structure of a male's courtship song differed significantly from his undirected song, and the structural differences between these two song types were not altered by AE treatment.     

Etiology of breast cancer III. Opportunities for prevention

Breast cancer, or its effects, may be preventable. Childbearing at an early age will confer some protection. Until there are other methods of primary prevention the physician must concentrate on secondary prevention, including screening. In presenting risk factors as criteria for screening we have attempted to make rational the use of screening technology. We should not easily accept screening for breast cancer as of proved value. Rather we must encourage clinical trials of various screening methods. In the meantime, while we engage in a moderate amount of screening we do so under the Scottish verdict of “not proven”.