MOSQUITO CYTOGENETICS. A REVIEW OF THE LITERATURE, 1953-62. (73/609)

Although an intensified interest in mosquito cytogenetics in the past decade has produced a number of contributions to knowledge on this subject, the available information is still superficial and limited to a few mosquito species only. The author of this review summarizes the research done in this field between 1953 and 1962.The following are some of the achievements and some of the gaps that remain to be filled. Karyotypes of several species of Anopheles, Aedes and Culex conform to the general pattern 2n=6, with heterosomes distinguishable only in Anopheles. At least three different karyotypes are present in Anopheles. Salivary gland chromosome maps are now available for several anopheline species, but are still lacking for Culex and Aedes. No precise correlation may yet be made between the frequency of chromosomal aberrations and the degree of insecticide-resistance. Sexual differences in the salivary X-chromosomes have been reported for several species of Anopheles. Chromosomal polymorphism is common in some anophelines, but rare in others. Chromosomal mutation has been induced by means of X-rays.In his conclusions, the author stresses that prospects are especially good for evolutionary and genetic studies involving chromosomal polymorphism.  (+info)

ALTERATION IN TRANSFORMABILITY OF DIPLOCOCCUS PNEUMONIAE AFTER THE ACQUISITION OF GENETIC DETERMINANTS INDUCING RESISTANCE TO ERYTHROMYCIN. (74/609)

Sirotnak, Francis M. (Sloan-Kettering Institute for Cancer Research, New York, N.Y.), Ramona B. Lunt, and Dorris J. Hutchison. Alteration in transformability of Diplococcus pneumoniae after the acquisition of genetic determinants inducing resistance to erythromycin. J. Bacteriol. 86:735-739. 1963.-The genetic alteration of a highly transformable (competent) recipient strain of Diplococcus pneumoniae by the transformation of at least two of three identified erythromycin-resistance determinants (Ery(a), Ery(b), Ery(c)) results in a marked decrease (Ery(a-b) recombinant) or complete loss (Ery(a-c) recombinant) in the ability to be transformed. The occurrence of transformable cells in cultures of the R6 Ery(a-b) recombinant strains, although greatly diminished, still varies during growth in a manner characteristic of the fully competent parent strain. Both Ery(b) and Ery(c) determinants appear to be linked to Ery(a). In experiments using P(32)-labeled deoxyribonucleic acid (DNA), data correlating DNA uptake with transformation show a decrease or loss in uptake capacity of the erythromycin-resistant strains.  (+info)

BIOSYNTHETIC LATENCY IN EARLY STAGES OF DEOXYRIBONUCLEIC ACIDTRANSFORMATION IN BACILLUS SUBTILIS. (75/609)

Nester, E. W. (University of Washington, Seattle) and B. A. D. Stocker. Biosynthetic latency in early stages of deoxyribonucleic acid transformation in Bacillus subtilis. J. Bacteriol. 86:785-796. 1963-In the Bacillus subtilis deoxyribonucleic acid (DNA) transformation system, transformants do not increase in number for 3 to 5 hr after the addition of DNA. During most of this period, the transformants are resistant to the bactericidal action of penicillin under conditions which result in the killing of over 90% of the recipient population. This lag in growth and nonmultiplication of the transformants (inferred from penicillin resistance) is also reflected in a lag in the synthesis of an enzyme specified by the donor DNA. Thus, when a cell population deficient in the enzyme tryptophan synthetase is transformed to tryptophan independence, activity of this enzyme cannot be detected in whole cells until 3 to 4 hr after the cells have been exposed to the DNA. Recombination between donor and recipient DNA occurs long before this. Even 30 min after exposure of a competent population of try(2) (-)his(2) (+) cells to try(2) (+)his(2) (-) DNA, 20% of the total try(2) (+) activity found in re-extracted DNA exists as recombinant DNA, try(2) (+)his(2) (+). This value, the maximal linkage obtained, remains constant during incubation of the DNA-treated culture for an additional 5 hr. In addition to the heterogeneous response of a DNA-treated competent culture to penicillin killing, the recipient culture appears to be heterogeneous in ability to undergo transformation. Thus, the frequency of joint transformation of two unlinked markers is much higher than would be expected on the basis of the random coincidence of more than one DNA molecule entering the same cell in a uniformly competent recipient population. A possible relationship between these two aspects of heterogeneity of a DNA-treated recipient population is discussed.  (+info)

EFFECTS OF CHRONIC EXCESS SALT INGESTION. ROLE OF GENETIC FACTORS IN BOTH DOCA-SALT AND RENAL HYPERTENSION. (76/609)

By selective inbreeding, two strains of rats were developed previously that differed markedly in their susceptibility to the development of experimental hypertension from excess salt ingestion (1, 2). The present report indicates that with animals derived from the same strains, similar differences in response were obtained in rats subjected to either combined desoxycorticosterone-NaCl (DOCA-salt) treatment or unilateral renal artery compression without extra dietary salt. Thus differences in genetic substrate appear to influence the development of experimental hypertension produced by these three techniques and possibly this may hold true for all "varieties" of experimental hypertension. If true, it might allow the development of a unifying hypothesis that could be relevant not only to experimental hypertension but perhaps to human hypertension as well. The DOCA-salt regimen was more toxic to the animals than unilateral renal artery compression. Tentatively, this was ascribed to either, or both, the younger age or the higher NaCl intake of the animals in the former.  (+info)

EXPERIMENTAL TRANSMISSION OF INFLUENZA VIRUS INFECTION IN MICE. II. SOME FACTORS AFFECTING THE INCIDENCE OF TRANSMITTED INFECTION. (77/609)

Evidence has been presented that with the experimental model described, infected mice vary in their ability to transmit influenza virus infection. This variation is not explained by differences in titers of influenza virus in the nose, throat, trachea, or lungs of good transmitters. Older mice acquire transmitted influenza virus infection more readily than younger mice. Seasonal variations in the incidence of transmitted influenza virus infection occur.  (+info)

CURRENT CONCEPTS OF CANCER. (78/609)

Because the cancerous change in cells appears to be a permanent alteration, handed on to daughter cells through innumerable divisions, it seems probable that it reflects an abnormality in the transfer of information from cell to daughter cells. Transfer of information in cells is believed to depend on their genetic apparatus, and transfer of abnormal information implies that the genetic apparatus is not functioning normally. Abnormalities in genetic material, whether induced by ionizing radiation, chemical compounds or viruses, would, if reproduced at cell division, reappear in daughter cells. If such abnormalities lead to cancerous change in cells, any one of these primary incitants might be effective. Under such circumstances, the nature of the primary incitant may not be the most important question, and definition of the nature of the abnormality in the genetic material may become the central problem. It may ultimately be feasible to explain the cancerous change in cells in chemical terms and to find that it represents a molecular disease which takes its origin from the emergence of abnormal nucleotide sequences in the genetic material. In biological terms this would correspond with an induced mutation which is heritable at the level of the somatic cell.  (+info)

FAMILIAL ATRIAL FIBRILLATION. (79/609)

Benign familial atrial fibrillation is of rare occurrence. A family in which three members manifested this disorder is reported. Apart from this, all three are in excellent health.The relative frequency of non-familial atrial fibrillation in otherwise well people, free from cardiac and metabolic disorders, is stressed. Only too frequently such cases have been and continue to be labelled with the stigma of serious disease with an unhappy prognosis. Serious injustice may be occasioned in such cases in many respects; for example, in the influence that this medical judgment may have on the insurability of young people so afflicted.Methods of exclusion of organic causes of this disorder are outlined and principles of management and treatment are discussed.  (+info)

RECIPIENT ABILITY OF SALMONELLA TYPHOSA IN GENETIC CROSSES WITH ESCHERICHIA COLI. (80/609)

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Stanley Falkow, and L. S. Baron. Recipient ability of Salmonella typhosa in genetic crosses with Escherichia coli. J. Bacteriol. 87:54-60. 1964.-Salmonella typhosa strain 643WS(r) was mated with Escherichia coli Hfr strains W1895 and Hayes, with single marker selection for the E. coli genes lac(+) (lactose utilization) and ara(+) (arabinose utilization). Four classes of Salmonella hybrids were obtained, each class possessing one marker derived from one E. coli parent. In a series of eight genetic crosses, in which each hybrid class was remated with each of the Hfr strains, recipient ability of the hybrids was increased only when their substituted E. coli genetic section matched the lead region of the Hfr chromosome. Data obtained from replica plating indicated that the S. typhosa 643WS(r) population is probably homogeneous with respect to its initial ability to mate with E. coli. Transfer of the F-lac element was found to occur only slightly less efficiently from an E. coli F' donor to S. typhosa than it did to an E. coli F(-) strain. This indicated that E. coli is able to conjugate almost as effectively with S. typhosa as it does intraspecifically. However, failure to detect beta-galactosidase production by merozygotes derived from an E. coli Hfr W1895 x S. typhosa mating indicated that transfer of chromosomal lac(+) may be impaired.  (+info)