A reply to Holmes on Gendercide

Warren's book, Gendercide: The Implications of Sex Selection (Totowa, N.J.: Rowman and Allanheld; 1985), was reviewed by Helen Bequaert Holmes in the January 1987 issue of Bioethics. Here, Warren responds to the review by clarifying some of her moral arguments and continuing to defend the point of view that selecting the sex of children before conception or before birth is not always sexist, socially harmful, or disrespectful of the child as an end in itself.     

Control of a teleost social signal

Territorial male Haplochromis burtoni (Teleostei; Cichlidae) have a dark facial stripe, the 'eyebar', which can appear and disappear within seconds, independently of other coloration patterns. It is used to signal territory ownership and aggressive intent. Some males, called 'barless', have functional melanophores in the eyebar region but never display this pattern, because melanin in eyebar pigment cells is never dispersed. The eyebar melanophores are controlled by a specialized branch of the maxillary nerve. Lesioning the 'eyebar nerve' resulted in immediate melanin dispersion and consequent darkening of the eyebar pattern, and it abolished the normal paling response in all behavioral situations. Nerve lesion produced similar results in both barred and barless males, except that the coloration of the denervated eyebar in barless males was more similar to camouflage markings than to the conspicuous black eyebar used as a social signal. Electrical stimulation of the maxillary nerve produced melanin aggregation. Photoelectric recordings of this paling response revealed no differences between barred and barless males, or between the eyebar and other facial chromatophores that do not function as visual displays. Thus, the difference in the physiological state of eyebar melanophores in intact barred and barless males cannot be explained by differences in peripheral nerve anatomy or physiology.     

Neurochemical evidence for two types of presynaptic alpha2-adrenoceptors

Neurochemical and pharmacological evidence has been obtained that noradrenergic varicosities (in mouse and rat vas deferens) and cholinergic varicosities (in the Auerbach's plexus) contain heterogenous alpha₂-adrenoceptors through which the release of [³H]noradrenaline and [³H]acetylcholine can be modulated. The quantitative data also support the hypothesis that different noradrenaline and xylazine sensitive alpha₂-adrenoceptors are present prejunctionally in the vas deferens and Auerbach's plexus preparations. Prazosin, although it has a presynaptic inhibitory effect on alpha₂-adrenoceptors of noradrenergic axon terminals, has no effect on cholinergic axon terminals. These data suggest that there are two different types of alpha₂-adrenoceptors at the presynaptic axon terminals.Special Issue Dedicated to Dr. Abel Lajtha     

Functional and structural analyses of mouse genomic regions screened by the morphological specific-locus test

Genetic analyses of certain classes of mutations recovered in the mouse specific-locus test (SLT) have characterized arrays of deletions, overlapping at the marked loci. Complementation maps, generated for several of the regions, have identified a number of functional units surrounding each marked locus and have ordered the mutations into complementation groups. Molecular entry to all but one of the marked regions has been achieved by (1) identifying proviral integrations in, or close to, the specific loci (d, se, a, c); (2) mapping random anonymous clones from appropriately enriched libraries to the longest deleted segments, then submapping to more limited segments on the basis of complementation and deletion-breakpoint maps (c, p); (3) similarly mapping known clones thought to be located in pertinent chromosomal regions (p, c, d); and (4) cloning specific genes that reside in regions corresponding to the deletions (b, c, p). The molecular analyses have confirmed that genetically-inferred deletions are structural deletions of DNA. The emerging physical maps are concordant with the complementation maps, and in several cases have discriminated among members of a complementation group with respect to breakpoint positions. Deletion-breakpoint-fusion fragments have prove to be highly useful for making large chromosomal jumps to facilitate physical mapping. The recent advances toward correlating physical and functional maps of specific regions of the mouse genome owe much to the existence of arrays of mutations involving loci marked in the SLT. In turn, the characterizations of these regions have made it possible to demonstrate qualitative differences among mutations resulting from different treatments. This new capability for qualitative analysis, which will increase as the molecular studies proceed, further enhances the value of the SLT, which has been extensively used for quantitative studies in germ-cell mutagenesis.     

Genetic deletions between directly repeated sequences in bacteriophage T7

Summary DNA sequence analysis of genetic deletions in bacteriophage T7 has shown that these chromosomal rearrangements frequently occur between directly repeated DNA sequences. To study this type of spontaneous deletion in more quantitative detail synthetic fragments of DNA, made by hybridizing two complementary oligonucleotides, were introduced into the non-essential T7 gene 1.3 which codes for T7 DNA ligase. This insert blocked synthesis of functional ligase and made the phage that carried an insert unable to form plaques on a host strain deficient in bacterial ligase. The sequence of the insert was designed so that after it is put into the T7 genome the insert is bracketed by direct repeats. Perfect deletion of the insert between the directly repeated sequences results in a wild-type phage. It was found that these deletion events are highly sensitive to the length of the direct repeats at their ends. In the case of 5 bp direct repeats excision from the genome occurred at a frequency of less than 10⁻¹⁰, while this value for an almost identical insert bracketed by 10 bp direct repeats was approximately 10⁻⁶. The deletion events were independent of a hostrecA mutation.     

V-Y advancement flaps for closure of nasal defects

The nose is a difficult anatomic region in which to close defects resulting from resection of cutaneous malignancies. The V-Y flap is a technique for advancing adjacent tissue, thereby achieving wound closure while minimizing tension. A total of 120 V-Y flaps were used to close 114 nasal defects. The average defect size was 13.5 x 11 mm. Partial flap loss occurred in five patients, with total flap loss in one. One wound infection and two hematomas occurred.     

Cytoskeletal involvement in spermiation and sperm transport

The process of spermiation and sperm transport was studied using specific inhibitors of cytoskeletal elements. Within 12-24 hr after the intratesticular injection of taxol, a compound that acts to stabilize microtubules and inhibit microtubule-related processes, an unusually large number of microtubules was seen within the body of the Sertoli cell. At the same time, transport of elements within the seminiferous epithelium was affected. At the end of stage VI of the cycle, step 19 spermatids were maintained in the deep recesses of the Sertoli cell and not transported to the rim of the seminiferous tubule lumen. At stage VIII, residual bodies remained at, or near, the rim of the tubule and were not transported to the base of the tubule. They underwent only partial degradation at this site, indicating that there may have been two phases involved in their dissolution--one autophagic and one phagocytic, but the latter did not occur since the residual bodies were not transported to Sertoli lysosomes at the base of the tubule. The observations suggest that microtubules are involved in transport processes within the seminiferous epithelium. Within 1-12 hr after the intratesticular injection of 500 microM cytochalasin D, a compound which interferes with actin-related processes, normal appearing tubulobulbar complexes were not present. The tubular portion (distal tube) of the complex did not initiate development. It was assumed that filaments (which were identified as such using NBD-phallacidin and the S-1 fragment of myosin) played an important role in the development of this portion of the complex. Cells did not eliminate cytoplasm normally, as evidenced by an enlarged cytoplasmic droplet, further emphasizing the published role for tubulobulbar complexes in cytoplasmic elimination. Although sperm were released normally from stage VIII tubules, many remained within the tubular lumen and did not traverse the duct system. Cytochalasin did not inhibit fluid secretion by the Sertoli cell, as demonstrated by efferent duct ligation, but did alter myoid cell actin cytoskeletal organization, suggesting that myoid cell contractility is primarily responsible for transport of sperm. Overall, the observations suggest that cytoskeletal activity of the Sertoli cell is important for several aspects of the spermiation process as well as sperm transport.     

More monensin-sensitive, ammonia-producing bacteria from the rumen

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.