Bitter taste of saccharin and acesulfame-K.

The relationships among suprathreshold taste responses to acesulfame-K, Na-saccharin and 6-n-propylthiouracil (PROP) were examined in two studies. In the first study, the labeled magnitude scale was used with the high anchor labeled as 'strongest imaginable oral sensation' and in the second study, it was labeled as 'strongest imaginable sensation of any kind'. Results from the two procedures were similar. Individual differences among 65 subjects were seen in bitter responses to acesulfame-K and saccharin. Bitter responses to acesulfame-K ands accharin were positively correlated, but showed no significant relationship with responses to PROP bitterness or with PROP taster groups. Saccharin and acesulfame-K may share a common mechanism for bitter taste reception and transduction, one that varies across individuals and is different from mechanisms mediating bitter responses to PROP. Changing the instructions of the labeled magnitude scale induced a context effect. Ratings of sweetness referenced to the 'strongest imaginable sensationof any kind' were lower than ratings referenced to just oral sensations.     

Enterovirus Recovery with Vegetable Floc

A lettuce floc was prepared and used for recovering enterovirus from an aqueous suspension. The method is simple, and the adsorption of coxsackievirus B5, echovirus 7, and poliovirus 1 is quantitative. The virus-floc complex may be removed from aqueous suspension by low-speed centrifugation and dissolved at an alkaline pH in a small volume of water; virus is then available for assay on cultured cells. Flocs from some other green vegetables also possess the property of virus adsorption     

Post-implantation development and cytogenetic analysis of diandric heterozygous diploid mouse embryos

Diandric heterozygous diploid mouse embryos were produced by standard micromanipulatory techniques using eggs from female mice with a normal chromosome constitution and fertilised by homozygous Rb(1.3)1Bnr males containing a pair of large metacentric marker chromosomes in their karyotype. The constructed diandric eggs were transferred to the oviducts of pseudopregnant recipients and subsequently autopsied midday on the eighth day of gestation. From a total of 85 eggs transferred to females that subsequently became pregnant, 30 implanted. Eighteen implantation sites were found to contain resorptions, and 12 egg cylinder stage embryos were recovered. These were cytogenetically examined. In two cases, no mitoses were observed, and in a third embryo of normal size, only a single paternally-derived marker chromosome was present in its mitoses, indicating that this embryo had a normal chromosome constitution. This presumably resulted from a technical error during the micromanipulatory procedure. The remaining nine morphologically small but normal embryos were diploid, and each had two paternally-derived marker chromosomes, thus establishing their ploidy and confirming their diandric origin. G-banding analysis revealed that all of these embryos had an XY sex chromosome constitution. Since the expected XX:XY:YY ratio of 1:2:1 was not observed, it is clear that the XX class embryos were lost at some stage during the pre- or early post-implantation period, though whether they are represented by the resorption sites is not yet established. The YY class would not be expected to be recovered in any case, as these embryos are believed to be lost during early cleavage. The cytogenetic findings reported here are therefore similar to the results of the chromosomal analyses of the human complete hydatidiform moles of dispermic origin, all of which apparently have an XY karyotype. It is unclear why, both in the human and in the mouse, the XX diandric heterozygous diploid group should develop poorly compared to similar embryos with an XY karyotype.     

Sex-chromosome constitution of postimplantation tetraploid mouse embryos

Tetraploid mouse embryos were produced at the two-cell stage by blastomere fusion induced by inactivated Sendai virus. The embryos were from chromosomally normal female mice that had been fertilised by homozygous Rb(1.3)1Bnr males carrying a pair of large metacentric marker chromosomes in their karyotype. These "reconstructed" one-cell tetraploid embryos were then transferred to the oviducts of pseudopregnant recipients, which were subsequently autopsied early on the 10th day of gestation. Two-cell stage embryos that did not undergo blastomere fusion after 4-5 h were transferred to a second group of recipients, which were also autopsied early on the 10th day of gestation. From a total of 153 tetraploid embryos transferred to females that subsequently became pregnant, 135 implanted. Sixty-eight implantation sites were found to contain resorptions, whereas 67 contained mostly headfold presomite-stage embryos. Four embryos possessed four to six pairs of somites. All 57 embryos that could be analysed cytogenetically were found to be tetraploid. G-banding analysis revealed that 30 of these embryos had an XXYY and 27 and XXXX sex-chromosome constitution. The presence of two marker chromosomes in all mitotic preparations from each of these tetraploid embryos confirmed that they had all been produced by duplication of their original XY or XX diploid chromosome constitution, respectively. The XXYY:XXXX sex ratio observed was not significantly different from unity. In the control series of transfers, all of the embryos recovered were at the forelimb bud stage and had a diploid chromosome constitution. The results reported here differ from human clinical findings, in which the XXYY:XXXX sex ratio of 120 human tetraploid spontaneous abortions recovered over the last 20 years is 45:75. Possible explanations for these differences are briefly discussed.     

Concentration of Enteric Viruses from Water with Lettuce Extract

A method for recovering enteroviruses, adenovirus, and reovirus from water with lettuce extract is described. Lettuce extract at pH 8.5 was added to the sample and the pH was reduced stepwise with hydrochloric acid to 4.0 to 4.5. The flocculent lettuce-extract particles, and adsorbed virus, were readily removed from solution by low-speed centrifugation. Electron microscopy suggests that, under conditions suitable for adsorption, virus particles are coated with the lettuce-extract colloid.     

Immunohistochemical investigations of neuropeptides in the brain,corpora cardiaca,and corpora allata of an adult lepidopteran insect,Manduca sexta (L)

In the brain of adult specimens of the tobacco hornworm moth, Manduca sexta (L), cells immunoreactive for several kinds of neuropeptides were localized by means of the PAP procedure, by use of antisera raised against mammalian hormones or hormonal peptides. In contrast, no such neurosecretory cells were found in the corpora cardiaca and corpora allata (CC/CA); in the CC/CA, however, immunoreactive nerve fibres were observed, reaching these organs from the brain. The neurosecretory cells found in the brain were immunoreactive with at least one of the following mammalian antisera, namely those raised against the insulin B-chain, somatostatin, glucagon C-terminal, glucagon N-terminal, pancreatic polypeptide (PP), secretin, vasoactive intestinal polypeptide (VIP), glucose-dependent insulinotropic peptide (GIP), gastrin C-terminus, enkephalin, alpha- and beta-endorphin, Substance P, and calcitonin. No cells were immunoreactive with antisera specific for detecting neurons containing the insulin A-chain, nerve growth factor, epidermal growth factor, insulin connecting peptide (C-peptide), polypeptide YY (PYY), gastrin mid-portion (sequence 6-13), cholecystokinin (CCK) mid-portion (sequences 9-20 and 9-25), neurotensin C-terminus, bombesin, motilin, ACTH, or serotonin. All the neuropeptide-immunoreactive cells observed emitted nerve fibers passing through the brain to the CC and in some cases also to the CA. In CC these immunoreactive nerve fibers tended to accumulate near the aorta. It was speculated that neuropeptides are released into the circulating haemolymph and act as neurohormones.