Middle ear effusion--a theoretical neuro mechanical hypotheses

An alternative theoretical neuro-mechanical hypothesis is presented in the pathogenesis of middle ear effusion, along with a review.

Factors influencing replicon organization in tissues having different S-phase durations in the mole rat, Bandicota bengalensis

In order to identify factors affecting the length of S-phase in mammals, DNA fibre autoradiograms from different tissues [bone marrow, phytohaemagglutinin (PHA)-stimulated spleen lymphocytes and whole body cells of new-borns] of the mole rat, Bandicota bengalensis, were examined for various parameters of replicon organization. The duration of S-phase in bone marrow and spleen was 12-14 h while that in new-borns was 8-9 h. Fork migration rate was significantly greater in new-borns than in bone marrow, and replicon size was significantly smaller in new-borns than in spleen. Thus it appears that several factors contribute, to varying degrees, in establishing the duration of S-phase in any cell type. In about 20% of the replicon clusters, constituent replicons were found to initiate replication asynchronously. This asynchronous initiation could possibly be due to an effect of transcription on time of initiation since it is likely that neighbouring replicons would be transcribed to different extents.

Do sister forks of bidirectionally growing replicons proceed at unequal rates?

DNA fibre autoradiography in different tissues of the rodents Bandicota bengalensis and Nesokia indica reveals a high frequency of such bidirectionally replicating replicons whose sister 'hot' tracks are of unequal size. These results suggest intrarepliconic difference in the rates of fork migration in the two directions.

Mammalian sex chromosomes. II. Pairing and alignment of the X and Y chromosomes of the pygmy mouse, Mus dunni

In the pygmy mouse, Mus dunni, the entire Y chromosome and the short arm of the X and distal region of its long arm are constitutively heterochromatic. Different banding studies on somatic chromosomes revealed the GC nature of the distally located heterochromatin of the long arms of both the X and Y chromosomes. The short arm of the X and the rest of the Y are AT-rich. During meiosis, the long arms of the X and Y paired extensively, sometimes more than half of the Y pairing with the X. This observation is in disagreement with that of Pathak and Hsu (1976) who reported end-to-end pairing between the long arm of the X and the short arm of the Y. The orientation observed by us is favourable to a successful meiotic recombination but whether this takes place remains to be demonstrated.

Mammalian sex chromosomes. I. Cytological changes in the chiasmatic sex chromosomes of the male musk shrew, Suncus murinus

The X and Y chromosomes of the musk shrew are the two largest in the complement and they regularly form a single chiasma during meiosis. This chiasma is located in the short arms of the X and Y, both of which show partial C-banding at meiosis. The in vitro incorporation of 5-bromodeoxyuridine/tritiated thymidine during late S reveals that the non-C-band region of the Y finishes replication later than the C-band positive heterochromatin. During meiosis, the sex bivalent opens out early in pachytene to reveal a single chiasma which persists until late metaphase-I. In surface-spread, silver-stained meiocytes, the sex bivalent morphology changes from a phase of extensive pairing to one which includes a visible chiasma through a brief diffuse stage. Observations on C-banded meiocytes show a shift in the sex pair from a C-band positive to a negative state as compared to their corresponding somatic pattern. Comparable changes are also observed in the sex bivalents of other mammals which undergo a chiasmatic exchange. This suggests that in addition to pairing homology, an alteration in the chromatin configuration may be necessary for crossing over to occur between the sex chromosomes.

Effects of Hoechst 33258 on different cell cycle events. I. Inhibition of synthetic activities in bone-marrow cells of the mole rat Bandicota bengalensis

A study of the effects of the A-T base-specific ligand Hoechst 33258 on the cell cycle events of the bone-marrow cells of the mole rat Bandicota bengalensis reveals that (1) the G2 phase is prolonged by 2 h; (2) the chromosomes are undercondensed to varying degrees in about 30% metaphases; (3) DNA as well as RNA synthesis is partially inhibited. Study on DNA fibre autoradiograms shows that despite the inhibition of DNA synthesis the average replicon size and rate of fork migration remain unchanged, but there is a marked asynchrony of initiation of replicons in replicon clusters in H-treated cells in comparison with control. It is suggested that these inhibitory effects result from the stabilization of the double-stranded organization of DNA (dsDNA) by the drug so that the unwinding of DNA at the replication or transcription origin sites is greatly impaired. It is likely that this introduces asynchrony in the initiation of replicons within replicon clusters which may retard the overall rate of replication. In addition, it appears that the reduction in transcription is at least one cause for the prolongation of G2 phase.

A simple method of staining the synaptonemal complex with Coomassie brilliant blue for light microscopy

A simple technique for staining synaptonemal complexes with Coomassie brilliant blue for light microscopy has been described. The testis cells were exposed to prolonged hypotonic treatment and dropped on Formvar-coated slides. Following fixation with paraformaldehyde the slides were stained with Coomassie brilliant blue for 15 min to 1 h at room temperature and rinsed in distilled water. For its simplicity and rapidity this technique may serve as an effective alternative to silver staining for light microscopic observation of synaptonemal complexes.

Identification and patterns of synapsis of the autosomally translocated Y-chromosome of the Indian mongoose, Herpestes auropunctatus (Hodgson)

The multiple sex chromosome system, X1X2Y male/X1X1X2X2 female, in the small Indian mongoose, Herpestes auropunctatus, results from a translocation of a part of Y chromosome to an autosome. It is not possible to distinguish the autosome which harbours the Y chromosome element in the somatic complement. By employing the surface-spreading technique to prophase I meiocytes we have identified the region to which the Y chromosome has been translocated as the short arm of chromosome 9 which is a subtelocentric chromosome. This Y chromosome component lacks heterochromatin and no sex vesicle is organised during meiotic prophase. This suggests to us that Y heterochromatin in mammals may be required for the production of a sex vesicle.

Cytological similarity between the heterochromatin of the large x and y chromosomes of the soft-furred field rat, Millardia meltada (family: muridae)

Patterns of DNA replication, fluorescence, and meiotic pairing have been studied in the composite X and Y chromosomes of a rodent, the soft-furred field rat, Millardia meltada. The heterochromatin of both the chromosomes replicated during late S and fluoresces brightly with Netropsin-Olivomycin. The fluorescence with Actinomycin D-Hoechst is dull, suggesting that the heterochromatin of both the X and the Y is relatively GC-rich. When surface-spread testis cells are analyzed after silver staining considerable portions of the X and Y exhibit synapsis. On the basis of this study it appears that the heterochromatin of the X chromosome of M. meltada is substantially similar to that of the Y chromosome.

Carcinoma of the palatine tonsil co-existing with tuberculosis

Summary

A CASE of carcinoma and tuberculosis occurring together in the palatime tonsil is reported. The relevant literature on the association of these two diseases has been reviewed.

Preferential late replication of one of the two morphologically distinguishable X-chromosomes in a female muntjac

In a female barking deer, Muntiacus muntjak, whose 2 X-chromosomes are mutually distinguishable from each other, one X has been found to be late replicating in 57.8% cells compared to the other which is late replicating in 42.2% cells. These data are suggestive of preferential inactivation of one X-chromosome. These findings have been discussed in the light of Lyon's hypothesis of random X-inactivation in eutherian mammals.

Unique multiple sex chromosomes of the tree mouse Vandeleuria o. oleracea: identification of X1 and X2

The tree mouse Vandeleuria o. oleracea has an odd diploid chromosome complement (2n = 29 female/male) accompanied by a unique multiple sex-chromosome mechanism (X1X2Ymale/X1X1X2female). In the present paper the sex chromosomes have been identified unequivocally with the help of G-banding and DNA replication patterns which confirm our earlier suggestion that the X1 is smaller in size than the simple mammalian X, and also that the combined sizes of the X1 and X2 (3-8 and 1-7 per cent respectively) approximate to the size of the conservative mammalian X (5 per cent). It is proposed that the mammalian X has attained a minimum functional size so that further reduction is not tolerated.

DIPOLE MOMENTS AND STRUCTURE OF MOLECULAR COMPOUNDS: PART I. ALIPHATIC AND AROMATIC AMINE PICRATES

Dipole moment measurements have been made for some aliphatic and aromatic amine picrates in dioxane solution. The fractional ionic character of these complexes in the ground state has been calculated from μN, the observed value of dipole moment; μ0, the vector sum of the moments of the components of the complex; μ1, the moment resulting from complete one-electron transfer; and known values of S, using the charge-transfer theory of Mulliken. For these complexes of the n + hσd type, the charge-transfer process lies in the direction of the symmetry axis N+O−, the picture corresponding to an energy of interaction U, versus charge-transfer co-ordinate (C) curve with a shallow minimum showing an inner complex corresponding to (C = 1), b = a2 or b2 > a2, and an activated complex (roughly between C = 0.3 to 0.5) corresponding to an intermediate.