Effect of “inverse melting transition” of aqueous triblock copolymer solutions on solute rotational dynamics

Rotational dynamics of two structurally similar hydrophobic solutes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP), has been investigated in 30% wv aqueous solution of triblock copolymer, poly(ethylene oxide)(20)-poly(propylene oxide)(70)-poly(ethylene oxide)(20) as a function of temperature. This study has been undertaken in an attempt to explore how the dynamics of a solute molecule solubilized in a copolymer solution is influenced when it undergoes sol-to-gel transition. It has been observed that the anisotropy decays of both DMDPP and DPP can be described by biexponential functions in the sol as well as in the gel phase. This observation has been rationalized on the basis of the probe molecule undergoing two different kinds of motion rather than being located in two different regions of the micelle. Even in the gel phase, which results as a consequence of micelle-micelle entanglement due to an increase in their volume fraction, the rotational relaxation of the solutes is similar to that observed in the micellar solution. The outcome of this work indicates that even though these gels have very high macroscopic viscosities and hence do not flow, the microenvironments experienced by the solutes are akin to that of a micellar solution.

Sodium Chloride and Ethanol Induced Sphere to Rod Transition of Triblock Copolymer Micelles

Dynamic light scattering (DLS), small-angle neutron scattering (SANS), and viscosity studies have been carried out to examine the influence of NaCl and ethanol on the structure of triblock copolymer [(EO)20(PO)70(EO)20] (EO = ethylene oxide; PO = propylene oxide) micelles in aqueous medium. The studies show that while the pure triblock copolymer solutions do not show any significant growth of the micelles on approaching the cloud point, the presence of a small amount of ethanol (5-10%) induces a sphere to rod shape transition of micelles at high temperatures. Interestingly, this ethanol induced sphere to rod transition of micelles can be brought down to room temperature (25 degrees C) with the addition of NaCl. It is also found that NaCl alone cannot induce such sphere to rod transitions and excess ethanol suppresses them by increasing their transition temperature.

Simulating thermal power plant processes on a message passing environment

Simulators play a very important role in the operation of thermal power plants and also in the design of control systems for these plants. To cater to this requirement elaborate methodologies have been developed to simulate thermal power plant processes in an interactive way. Due to the intensive computations involved, such simulators use one or more high through-put computers known as the simulation computers. This paper puts forward a method where parallel processing on a low latency message passing environment has been used to simulate thermal power plant processes following a modular approach. This eliminates the need of an expensive high through-put simulation computer, thus cutting down the hardware cost associated with a simulator and increasing the system reliability manifold.

Forty years of solitude: life-history divergence and behavioural isolation between laboratory lines of Drosophila melanogaster

The study of the early stages of speciation can benefit from examination of differences between populations of known history that have been separated for a short time, such as a few thousands of generations. We asked whether two lines of Drosophila melanogaster that were isolated more than 40 years ago have evolved differences in life-history characters, or have begun to evolve behavioural or postzygotic isolation. One line, which is resistant to DDT, showed lower egg production and a shorter lifespan than a susceptible line. These differences are not a pleiotropic effect of resistance because they are not attributable to the chromosome that contains the resistance factors. The two lines have begun to become behaviourally isolated. Again, the isolation is not attributable to genes on the chromosome that contains resistance factors. The lines show only prezygotic isolation; there is no evidence of reduced fitness of F1 or F2 hybrids. These lines and others like them, should be excellent subjects for analyses of genetic changes that could lead to speciation.

Squatting, blood pressure and stroke

Most Indians still adopt squatting posture in toilets. In a group of 67 healthy volunteers, squatting produced a small (8.09 +/- 7.04 mm Hg) but significant rise in systolic blood pressure (SBP) but not in diastolic (DBP). However, in a group of randomly selected treated hypertensives (N=104) squatting produced a much greater and significant rise in both SBP (14.46 +/- 11.63 mm Hg) and DBP (9.10 +/- 9.19 mm Hg). The possible clinical significance of this rise of BP in squatting has been evaluated in 100 consecutive CT proved patients with stroke by analysing their stroke onset data in relation to time, place, posture and activity. Most strokes (52%) occurred in the morning hours (5 am-9 am) and at home (86%) and over a third (36%) while in toilets. Thirty six percent of strokes occurred when the subjects squatted, mostly during defecation. More than half of hemorrhagic strokes occurred in the squatting position. The relationship of these clinical observations with the BP changes noted above on squatting appears to be more than fortuitous. We would suggest that hypertensive subjects and those at risk of stroke should avoid squatting and urge physicians to check squatting BP while monitoring anti-hypertensive therapy.

Is squatting a triggering factor for stroke in Indians?

BACKGROUND

Undocumented observations of ours suggested increased occurrence of strokes in the early hours of the morning and in the toilets where most Indians still squat. The present study has been designed to assess the validity of this observation and to identify the likely triggering factor in stroke onset in such situations.

MATERIAL AND METHODS

Part A of the study looked into stroke onset data of 100 consecutive CT-confirmed stroke patients specially in relation to time of day, place, posture and activity of the individual. Part B of the study included 67 healthy volunteers (age 24-49 years) whose supine and squatting blood pressure (BP) were measured and the differences noted. Part C of the study consisted of repeating the same procedure in 104 known hypertensives on treatment (age 28-60 years).

RESULTS

Part A of the study revealed that most strokes (52%) occurred in the morning and at home (86%) and over a third (36%) while in toilets. Thirty-six per cent of the strokes occurred while the subjects squatted, mostly during the act of defecation. More than half of the haemorrhagic strokes occurred while the subjects were in squatting position. In normal healthy volunteers squatting produced a small (8.09 +/- 7.04 mmHg) but significant rise in systolic blood pressure (SBP) but not in diastolic blood pressure (DBP) (0.9 +/- 7.38 mmHg). In contrast, in treated hypertensives squatting produced a significantly higher rise in both SBP (14.49 +/- 11.63 mmHg) and DBP(9.10 +/- 9.19 mmHg).

CONCLUSION

The relationship of the clinical observations regarding stroke onset with the BP changes noted on squatting in healthy as well as hypertensive subjects appears to be more than fortuitous. Squatting induced rise in BP appears to be an important triggering factor for stroke onset in subjects at risk in India.

Factors on the third chromosome affect the level of cyp6a2 and cyp6a8 expression in Drosophila melanogaster

The expression of two second chromosome-linked cytochrome P450 genes, Cyp6a2 and Cyp6a8, of Drosophila melanogaster was measured in various strains. Six different strains, including ry(506) and 91-C, showed low or undetectable levels of CYP6A2 and CYP6A8 mRNAs, suggesting that low expression is the wild-type phenotype of Cyp6a2 and Cyp6a8 genes. In the 91-R and MHIII-D23 strains, however, both these genes are overexpressed. In order to examine the genetic basis of Cyp6a2 and Cyp6a8 expression, CYP6A2 and CYP6A8 RNA levels were measured in the F1 hybrids of overproducer (91-R and MHIII-D23) and underproducer (ry(506) and 91-C) strains. Results showed that the total amounts of CYP6A2 and CYP6A8 mRNAs in the F1 hybrids were lower than half the amounts of these RNAs found in the overproducer parental strains. This suggested that the underproducer strains carry loci which downregulate Cyp6a2 and Cyp6a8 gene expression. To determine the chromosome linkage of these loci, several stocks homozygous for the second chromosome of overproducer 91-R strain and, therefore, homozygous for the Cyp6a2-91R and Cyp6a8-91R alleles were synthesized. The third chromosomes in all these stocks were from the underproducer ry(506) strain. The levels of expression of both Cyp6a2-91R and Cyp6a8-91R genes in these three stocks were significantly lower than that observed in the 91-R strain. One of these stocks, named iso-2, showing reduced expression, was used to synthesize two new isogenic stocks by resubstituting the third chromosome of ry(506) origin with third chromosomes of the 91-R strain. Expression of both Cyp6a2-91R and Cyp6a8-91R alleles was found to be much higher in these two resubstituted isogenic stocks than in the progenitor iso-2 stock. Taken together, these results suggest that the second chromosome-linked Cyp6a2 and Cypa8 genes are regulated by loci present on the third chromosome, and the wild-type function of these loci is to repress these two Cyp genes. The data also suggest that Cyp6a2 and Cyp6a8 overexpression in the 91-R and MHIII-D23 strains is more likely due to mutation in the repressor locus (or loci) rather than in the cis-regulatory sequences of the Cyp6a2 and Cyp6a8 genes.

Exposure of medical students to body fluids

Three hundred forty-two students at 3 Florida medical schools were surveyed concerning occupational exposures to blood and body fluids during their 3rd-year clerkship. The 16-item questionnaire was anonymously returned by 150 students, and differences among groups were assessed at p < .05. Most of the students complied with universal precautions guidelines (UVPG); 62 reported 101 exposures, including 9 with HIV-positive blood and body fluids. Most of the exposed students knew about the guidelines but regarded the incidents as irrelevant to their safety or supervision training. Noncompliant students reported significantly more exposures than compliant students. Time constraints, inconvenience of using gloves during procedures, and belief that patients were at low HIV risk discouraged adherence to the guidelines. Common practices following exposure were "no action" or "washed area only" without medical follow-up. Medical students' UVPG adherence should be increased by workload modification, user-friendly safety products, and supervised practice training in clinical exposure settings.

Constitutive and barbital-induced expression of the Cyp6a2 allele of a high producer strain of CYP6A2 in the genetic background of a low producer strain

The levels of one or more cytochrome P450 (CYP) enzymes and the respective mRNAs are found to be higher in insecticide-resistant insects than in susceptible insects. To understand better how insects regulate the levels of CYPs, we examined the expression of the Cyp6a2 gene in various strains of Drosophila melanogaster. We also took a transgenic approach to understand the molecular mechanisms that are involved in strain variation of Cyp6a2 expression. RNA blot analysis showed that the constitutive expression of Cyp6a2 varies from strain to strain; the level of CYP6A2 mRNA is barely detectable in the underproducer ry506 strain, whereas it is very high in the overproducer 91-R and MHIII-D23 strains. The long terminal repeat (LTR) of mobile element 17.6 that is found in the 3' untranslated region (UTR) of the Cyp6a2 gene of some strains does not appear to have any role on the steady-state CYP6A2 mRNA level. We also found that the Cyp6a2 gene is inducible by barbital in 91-R, ry506 as well as 91-C, which carries an LTR insertion. To examine the genetic background of the underproducer ry506 strain with respect to Cyp6a2 expression, we transformed the ry506 strain with the Cyp6a2 allele of the overproducer 91-R strain (Cyp6a2-91 R) and measured the constitutive and barbital-induced expression of the Cyp6a2-91 R transgene in the transformed flies. The Cyp6a2-91 R transgene carrying 129 bp of DNA upstream of the ATG codon did not show any constitutive or barbital-induced expression in the ry506 host genome. However, transgenes with 1331 and 985 bp upstream DNA showed similar levels of constitutive expression that were higher than that of the endogenous Cyp6a2 gene of the ry506 host strain, but lower than the expression of the same gene in the 91-R strain. Both these transgenes, with 1331 and 985 bp upstream DNA, also showed induction with 0.1 M barbital. DNA sequence analysis revealed that in both 91-R and ry506, the upstream DNA between +1 and -985 bp contains a distal and a proximal group of three potential barbie boxes, i.e. cis-elements that are thought to be involved in barbiturate-mediated induction of CYP genes. Except for four bases located near the distal cluster of barbie boxes and two other bases, the base sequence of the upstream DNA is identical in ry506 and 91-R strains. These results suggest that the underproducer ry506 strain has the trans-regulatory factors to support constitutive and induced expression of the Cyp6a2-91 R allele carrying DNA between -129 and -1331 bp regions. Possible reasons for low constitutive expression of the endogenous Cyp6a2 gene and moderate level of expression of the Cyp6a2-91 R allele in the ry506 genetic background are discussed.

Hepatitis B immunization in a university student population

In the United States, hepatitis B virus infection occurs predominantly among adolescents and young adults, despite the availability of an effective vaccine. Immunization status and hepatitis B virus (HBV) vaccine acceptance among 505 students visiting the student health services of a large southern university were investigated. Only 58 students had received HBV vaccine. The cost of the vaccine was paid by the students personally (35.5%) or by their parents (34.5%) or employers (31.0%). Nearly half of the students (45.7%) did not know their vaccination status. Lower immunization percentages were found among Hispanics, men, persons of lower education levels, and students aged 25 years and under. Being immunized was related to the perception that the vaccine was affordable, although most students (95.7%) said that the cost of HBV vaccine was excessive. Health professionals' emphasis on the need for HBV vaccination and a reduction in the price of the vaccine could improve HBV immunization rates among university students.

Three second chromosome-linked clustered Cyp6 genes show differential constitutive and barbital-induced expression in DDT-resistant and susceptible strains of Drosophila melanogaster

The level of expression of the Cyp6a2 gene is much higher in the DDT-resistant 91-R strain than in the susceptible 91-C strain of Drosophila melanogaster (Waters et al. (1992b) Proc. Natl. Acad. Sci. USA, 89, 4855-4859). To understand the role of Cyp6a2 and related genes in insecticide resistance, we have isolated and characterized two new Cyp6 genes from the 91-R strain. The polypeptides encoded by these two genes, Cyp6a8 and Cyp6a9, show 77 and 75% amino acid sequence similarity, and 60 and 55% identity with Cyp6a2 of D. melanogaster, respectively. In the genome, Cyp6a8 and Cyp6a9 genes are closely clustered within 4 kb and map at region 51C of the second chromosome. In between them another Cyp gene is present which is more related to Cyp6a9 than to Cyp6a8. The Cyp6a8 gene which is transcriptionally highly active in 91-R, moderately active in ry506 and silent in the 91-C strain hybridizes with 2.0- and 1.8-kb RNAs. Two different-sized RNAs, 2.1 and 1.8 kb, also hybridize with the Cyp6a9 and/or Cyp6a9-related genes. While the level of 2.1-kb RNA is similar in all three strains, the level of 1.8-kb RNA is highest in the 91-R strain and barely detectable in 91-C strain. Transgenic experiments showed that a 8.3-kb BamHI fragment contains the cis-regulatory elements for the expression of both Cyp6a8 and Cyp6a9-related genes. Barbital induces all these genes in all three strains and increases the levels of the two Cyp6a8 transcripts and the 1.8-kb RNA produced by the Cyp6a9 and/or Cyp6a9-related genes. Expression of the Cyp6a8 gene is down-regulated in the hybrids of 91-R and 91-C strains despite the fact that the hybrids carry one copy of the highly active allele of the Cyp6a8 gene of the 91-R strain. Based on these results we propose that the Cyp6a8 gene in 91-C strain may be turned off by an active repressor which might be inhibited by barbital treatment. In the 91-R strain, the putative repressor may be defective, allowing high level of constitutive expression of the Cyp6a8 gene.

A 3.5-kb DNA fragment contains the cis-regulatory elements for retina-specific expression and partial dosage compensation of the Arrestin B (ArrB) gene of Drosophila miranda

A 3.5-kb genomic DNA fragment containing the X1R chromosome-linked retina-specific Arrestin B gene (also called Arrestin 2) of Drosophila miranda (ArrB-mr) was introduced into the Drosophila melanogaster genome via germ-line transformation. The results showed that the ArrB-mr transgene was expressed only in the retina of the transformed flies. The transgene also showed male-specific transcriptional hyperactivation or dosage compensation, but the level was found to be 71-79% of the expected value. The endogenous autosomal ArrB-ml gene of D. melanogaster, as expected, was not found to be dosage compensated in the transformants. Thus, while the cis-regulatory elements for retina-specific expression are fully present in the 3.5-kb DNA, part of the sequences needed for full dosage compensation are missing in this DNA. Nucleotide (nt) sequence comparison of the upstream DNA revealed that both ArrB-mr and ArrB-ml possess a putative TATA box at -32 nt. They also have an 11-bp motif (5'-AATCCAGTTAG) similar to the photoreceptor conserved element I (PCE I) believed to play an important role in retina-specific expression of the D. melanogaster opsin and mouse Arr genes. In addition, both genes contain a TGACCT motif which is known to bind a transcription factor activated by retinoic acid and vitamin D3. However, five tandem repeats of a heptanucleotide sequence (TGGGCNR) and a 29-bp sequence with the potential to form a stem-loop structure, are found only in the ArrB-ml gene. These sequences may play an important role in dosage compensation of the X1R-linked ArrB-mr gene.

Influenza vaccination in the elderly

This study analyzed influenza vaccination in a group of elderly veterans living in a Florida VA nursing home care unit (NHCU). A survey questionnaire, developed to assess veterans' vaccination status, attitude and perception, was presented orally by a technician in the form of an interview and the responses were annotated in appropriate areas of the questionnaire. Only 34% of the 202 veterans had been vaccinated within the last 12 months (compliant group), although the study subjects were in a high-risk group, i.e., 65 years of age or older, an average length of stay at the NHCU of 12 months and > 70% suffered from chronic disease(s) with a past history of smoking. Thus, the veterans not vaccinated outnumbered those who were by 2:1. Vaccine acceptance was significantly influenced by physician's advice and the subject's knowledge and fear about the vaccine. Veterans advised to take the vaccine yearly, within the last 5 years and more than 5 years ago had vaccination rates of 96.4, 57.8 and 17.6%, respectively. Veterans never instructed had an immunization rate of 0%. Over half of the veterans (50.7%) had regular contact with a physician. Therefore, more frequent physician reminders to vaccinate could enhance the yearly vaccine coverage rate. Subjects who received the vaccine previously but failed to do so on a yearly basis acted out of fear of side effects and shots (most frequent reason given; 34.3% of all reasons), misconceptions about the vaccine recommendation (27.6%), as well as lack of motivation (19.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Organization and expression of the Drosophila melanogaster D-G gamma 1 gene encoding the G-protein gamma subunit

The organization and expression of the Drosophila melanogaster G-protein gamma subunit-encoding gene (D-G gamma 1) were analyzed. The results showed that the three D-G gamma 1 RNAs (1.1, 1.3 and 2.6 kb) are differentially expressed in different tissues. While the 2.6-kb RNA is found only in the neural tissues of late embryo, larva and adult, the 1.3-kb RNA is expressed only in the adult ovary. The 1.1-kb RNA, on the other hand, is predominantly expressed during embryogenesis and in the neural tissues of late embryo, larva and adult. Moderate expression of this RNA is also found in the imaginal discs and other larval tissues. Nucleotide (nt) sequence analysis showed that the 70-amino-acid polypeptide encoded by the 1.3-kb transcript of D-G gamma 1 is the same as that encoded by the 1.1- and 2.6-kb D-G gamma 1 transcripts reported earlier [Ray and Ganguly, J. Biol. Chem. 267 (1992) 6086-6092]. Both the 1.3- and 1.1-kb RNAs utilize the same polyadenylation site, but their 3'-UTR are 1662 nt shorter than that of the 2.6-kb RNA. Although transcription of all three RNAs starts at the same transcription start point (tsp), the 5'-UTR of the 1.3-kb RNA is 190-nt longer than that of the other two RNAs, due to the utilization of an 3' alternative splice site.(ABSTRACT TRUNCATED AT 250 WORDS)

Barriers to immunization--an examination of factors that influence the application of pneumococcal vaccine by house staff

Pneumococcal infection is a leading cause of adult morbidity and mortality in the United States. Immunization against this infection is a valuable strategy in preventive medicine. An effective pneumococcal vaccine has been available in this country for over a decade, but it remains poorly utilized. The purpose of the present investigation was to analyse the factors that affect the use and administration of the pneumococcal vaccine and to identify barriers to use. Upper-level internal medicine residents (n = 33) from two medical clinics associated with an academic medical centre completed an explanatory survey. This explored the levels of house-staff knowledge, perception and attitudes regarding the vaccine and the existence of practical barriers against its utilization. chi 2 analyses and z tests were carried out to determine significance, where appropriate. The majority of the house staff (22, 66.7%) answered correctly regarding vaccine target groups, and all residents indicated that they generally obtain a vaccination history in adult patient evaluation. However, a sizeable number (14, 42.4%) did not indicate a time of the year when they routinely administered vaccines to patients. They were not confident about their knowledge regarding vaccine guidelines (23, 69.7%) and had an exaggerated fear of hypersensitivity reactions from immunization (20, 60.6%). Neither the expense of the vaccine nor adverse publicity were impediments to immunization (24, 72.7% and 28, 84.8%, respectively). Although most physicians knew of the usefulness of the vaccine (31, 93.9%), many failed to translate this knowledge into clinical practice (22, 66.7%). 'Pressing' clinical issues were viewed as barriers to vaccination (18, 54.5%) and placed the practice of preventive medicine in a subordinate position.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid adenoma in northern Nigeria

A middle-aged farmer and a female student presented with osteitis fibrosa cystica with nephrocalcinosis in the former and nephrolithiasis in the latter due to primary hyperparathyroidism. Hypercalcaemia was present in both cases and neck exploration revealed a large solitary parathyroid adenoma which was excised. Because primary hyperparathyroidism is less common in tropical countries doctors may be less familiar with the early manifestations of the disease. The number of patients thus undiagnosed and untreated is unknown.

Characterization of a Drosophila melanogaster gene similar to the mammalian genes encoding the tyrosine/tryptophan hydroxylase activator and protein kinase C inhibitor proteins

A cloned 1.3-kb cDNA that hybridizes to genomic clone 549, containing genes predominantly expressed in the head of Drosophila melanogaster, was characterized. DNA sequencing showed that the cDNA-encoded protein is similar to a family of mammalian proteins, called 14-3-3, which activate tyrosine hydroxylase (TyrOHase) and tryptophan hydroxylase (TrpOHase), the two key enzymes regulating biosynthesis of biogenic monoamine neurotransmitters, such as dopamine and serotonin, in the brain. The putative D. melanogaster 14-3-3 protein (D14-3-3) shares 72.4, 74.3 and 78.3% amino acid (aa) sequence identity and 83.5, 87.7 and 85.9% aa sequence similarity with the beta, gamma and eta forms of bovine 14-3-3 protein, respectively. A lower (71%), but significant level of aa sequence identity was also found between D14-3-3 and sheep brain protein kinase C inhibitor protein (KCIP). The D14-3-3 gene expresses 1.0-, 1.9- and 2.9-kb mRNAs which show differential expression patterns. While the 2.9-kb mRNA is expressed only in the head, the other two mRNAs are found both in the head and body. Compared to the 1.9- and 2.9-kb mRNAs, the 1.0-kb mRNA is more abundant in the ovary and is probably maternally inherited. The 1.9-kb mRNA is the most predominant species in the embryos and its level peaks between 6-15 h of embryogenesis. The D14-3-3 gene is predominantly expressed in the ventral nerve cord of the embryo, and in the neural tissues of the head.(ABSTRACT TRUNCATED AT 250 WORDS)

The Drosophila G protein gamma subunit gene (D-G gamma 1) produces three developmentally regulated transcripts and is predominantly expressed in the central nervous system

A genomic clone, 536, located at the 44CD region of polytene chromosomes of Drosophila melanogaster, has been characterized for its neurobiological importance. We found that this clone contains a gene which produces 2.6-, 1.3- and 1.1-kilobase (kb) RNAs. While the 2.6-kb RNA is expressed only in the head, the 1.3-kb RNA is present exclusively in the body. The 1.1-kb RNA, however, is found in both the head and body, but in much higher concentration in the head. DNA sequence analysis of a 2.6-kb RNA-specific cDNA showed that this gene encodes a 70-amino acid polypeptide which is the putative Drosophila homologue to the gamma subunit of the bovine G-protein. The Drosophila protein, named D-G gamma 1, shares 46, 43, and 28% identity, and 59, 52, and 60% similarity, with the gamma 2, gamma 3, and gamma t proteins of bovine G proteins, respectively. Sequencing of the 1.1-kb RNA-specific cDNA clone revealed that the 1.1-kb RNA is produced from the 2.6-kb transcription unit by usage of an alternative polyadenylation site, and has a coding region identical to that of the 2.6-kb RNA. Genomic Southern blot hybridization indicated that the Drosophila genome has only one D-G gamma 1 gene. Throughout development the 1.1-kb RNA is found to be the most prevalent species; its level peaks between 9 and 12 h of embryogenesis. As is the case for the other G protein genes of Drosophila, the D-G gamma 1 gene is predominantly expressed in the central nervous system of the fly.

A BamHI repeat element is predominantly associated with the degenerating neo-Y chromosome of Drosophila miranda but absent in the Drosophila melanogaster genome

In Drosophila miranda, females have two X1 and two evolving X2 chromosomes, and males have one of each of these two X chromosomes and a Y chromosome. In males, the homologue of the X2 chromosome, the neo-Y chromosome, is attached to the Y chromosome and is under the process of degenerative evolution. We have examined a developmentally regulated X2/neo-Y chromosome-linked gene, 549mr, of D. miranda and found that the neo-Y chromosome-linked copy of this gene (549mr-NY) contains an insertional DNA. We discovered that sequences similar to those in the insertional DNA are present in multiple copies in the genome of both sexes of D. miranda but are more abundant in the males. The insertional DNA also identified a 1.1-kilobase BamHI repeat that is present in at least 6-fold excess in the male genome as compared to the female. This BamHI repeat and similar DNA sequences are predominantly concentrated on the evolving neo-Y chromosome, but very few are found on the homologous X2 and other chromosomes. The BamHI repeat also hybridizes with 2.0- and 1.8-kb RNAs and many other RNA species, which together are also approximately 6-fold greater in males. No sequences similar to the BamHI repeat are found in Drosophila melanogaster. Moreover, the BamHI repeat is not homologous to P, copia, or other D. melanogaster transposable elements. This repeat, named the NY element, may be involved in gene disruption and the process of degenerative evolution of the neo-Y chromosome.

Dosage compensation of a retina-specific gene in Drosophila miranda

The X1R chromosome of Drosophila miranda and the 3L autosome of Drosophila melanogaster are thought to have originated from the ancestral D chromosomal element and therefore may contain the same set of genes. It is expected that these genes will be dosage compensated in D. miranda because of their X linkage. To test these possibilities and to study evolution of the dosage compensation mechanism, we used the 3L-linked autosomal head-specific gene 507 ml of D. melanogaster to isolate the homologous gene (507mr) from a D. miranda genomic library. In situ hybridization showed that gene 507 is located at the 12A region of the X1R chromosome of D. miranda, indicating that the chromosomal homology deduced by cytogenetic means is correct. Restriction analysis and cross-specific DNA and RNA blot hybridization revealed the presence of extensive restriction pattern polymorphism and lack of sequence similarity in some areas of the 507mr and 507 ml DNA, including the 3' portion of the transcribed region. However, the 5' portion of the transcribed region and the DNA sequences, located approximately 0.8 kb upstream and 3 kb downstream from the 507 ml gene showed a high degree of similarity with the DNA sequences of comparable regions of the 507mr gene. In both species gene 507 codes for a highly abundant 1.8 kb RNA which is expressed in the retina of the compound eye. Although in D. miranda the males have one and the females have two copies of the 507 gene, the steady-state levels of the 507 mRNA in both sexes were found to be similar, indicating that gene 507 is dosage compensated in D. miranda.(ABSTRACT TRUNCATED AT 250 WORDS)