Evidence for Alpha-MSH Binding Sites on Human Scalp Hair Follicles: Preliminary Results

Alpha-MSH, considered an important pigmentation hormone, binds to melanocytes and is thought to stimulate melanogenesis through a cyclic-AMP-dependent mechanism. The binding of alpha-MSH to follicular melanocytes has been investigated in human hair of different colors, ranging from black to blond and senile white. Hairs were plucked, the follicles were cut off, and an alpha-MSH binding assay, using a radiolabeled alpha-MSH analogue, was performed on these bulbs. As controls of each assay, fragments of hairs of the same person were used. The results show a dose-response relationship and the assay seems to be specific for alpha-MSH, because other peptides such as ACTH, beta-LPH and beta-endorphins do not compete for binding sites as alpha-MSH does. These binding sites seem to be present only on melanin synthesizing melanocytes, since the controls and follicles of senile white hair, which do not contain active melanocytes, show negative results. All the assays were performed on raw material, i.e., whole plucked hair follicles. This is the first time that binding sites for alpha-MSH have been demonstrated on human scalp hair follicles. In addition, their presence was found to be associated with active melanin production; their absence was demonstrated on senile white hair follicles.     

In vitro cultivation of Diplostomum spathaceum and Diplostomum phoxini metacercariae

Using a new egg macerate medium Diplostomum spathaceum metacercariae were cultured to the stage of egg production for the first time, and an improved vitelline and growth response was obtained in Diplostomum phoxini. The importance of physical factors in the cultivation of strigeoid trematodes was demonstrated. Methods involving a continuous circulating system, diphasic media, a double culture tube technique or the chorio-allantoic membrane proved to be of no value in the cultivation of Diplostomum spp. The addition of selected hormones with known growth promoting properties did not have an appreciable effect on D. phoxini cultures. Supplementation of egg macerate cultures with various nutrients had only slight or no beneficial effect. The ability to use stored metacercariae for cultures was demonstrated.     

The coelomic envelope to vitelline envelope conversion in eggs of Xenopus laevis

An amphibian egg recovered from the body cavity is enclosed by a coelomic egg envelope. Upon transport down the oviduct, the envelope is converted to the vitelline envelope. The coelomic and vitelline envelopes are distinct in terms of sperm penetrability, ultrastructural morphology, and radioiodination profiles. In this study, the macromolecular compositions of these two envelopes were determined. Isolated envelopes were compared by one- and two-dimensional gel electrophoresis, peptide mapping, and radiolabeling. A protein with a molecular weight of 57,000 (57K) was present in the vitelline envelope but was absent in the coelomic envelope. A glycoprotein with a molecular weight of 43K in the coelomic envelope was converted to a component with a molecular weight of 41K in the vitelline envelope. The 43K-molecular weight component of the coelomic envelopes could be radioiodinated by lactoperoxidase but no labeling of the 41K-molecular weight component occurred in the vitelline envelope. Peptide mapping using limited proteolysis established that the 43K-molecular weight component of the coelomic envelope was a precursor to the 41K-molecular weight component of the vitelline envelope. These molecular alterations may underlie the ultrastructural and physiological changes occurring in these envelopes.     

Vitelline layer lytic activity in sperm extracts of sea urchin,Hemicentrotus pulcherrimus

A factor which dissolves the vitelline layer was extracted from sperm of the sea urchin, Hemicentrotus pulcherrimus. Turbidity of the suspension was reduced when isolated vitelline layers were mixed with this sperm factor. When the mixture was subjected to SDS polyacrylamide gel electrophoresis, some of the protein bands of the vitelline layer were seen to be missing. The lytic activity of the factor was heat labile, completely inhibited by L-1-tosyl-amide-2-phenyl-ethylchloromethyl ketone and partially inhibited by soybean trypsin inhibitor. Chymotrypsin activity was detected, but not trypsin, arylsulfatase, or glycosidase. These results suggest that a chymotrypsin-like enzyme participates in lysis of the vitelline layer by the fertilizing spermatozoon.     

Electrically mediated protein movement inDrosophila follicles

Summary Distribution of rhodamine-conjugated lysozyme injected into the sixteen-cell syncytium comprising the germ-line portion of theDrosophila follicle is shown to be affected by charge. Positive molecules are able to migrate through intercellular bridges from the oocyte to the nurse cells, but are unable to migrate detectably from nurse cells to the oocyte. Their negatively charged counterparts can move from the nurse cells to the oocyte, but are unable to traverse the intercellular bridges in the counter direction. This charge-dependent movement of molecules is accompanied by an electrical potential difference, focused across the nurse cell-oocyte bridges, which makes the nurse cells negatively charged to the oocyte. The addition of insect hemolymph to the physiological salt solution in which the experiments were performed resulted in only a small increase in the transmembrane resistance, but enhanced the potential difference between oocyte and nurse cells from 0.2±0.3 (SE) mV (nurse cells negative) to 2.3±0.45 (SE) mV (nurse cells negative). Supported by NSF Grant # DB-18617     

Habitat, reproductive biology and size composition of Parequula melbournensis, a gerreid with a temperate distribution

Trawling was carried out over sandy substrates in the shallow (5–15m) and deeper (20–35m) waters of four regions along 250 km of the lower west coast of Australia, during seven consecutive seasons. This yielded 32 752 individuals of the gerreid Parequula melbournensis , which constituted c. 42% of the total number of fish. Densities of P. melbournensis were greatest in the most southern region, reaching a seasonal maximum of 835 fish ha⁻¹: at one site in that region. Since P. melbournensis is restricted largely to the southern coastline of Australia, it has a temperate rather than subtropical or tropical distribution and thus is not a typical gerreid. Furthermore, unlike most other gerreids, it does not spend part of its life cycle in either estuaries or nearshore marine waters. The maximum total length of P. melbournensis was 175 mm, with the length at maturity ( L ₅₀) being 115 mm in females and 121 mm in males. No clear monthly trends were exhibited by gonadosomatic indices, the prevalence of mature ovaries and the oocyte size-frequency distributions of female P. melbournensis , and no clear and consistent modes were observed in length-frequency data for this species. These strong indications that spawning occurs throughout the year were substantiated by the occurrence of post-ovulatory follicles in the ovaries of large fish in all months but August, and by the presence in that month of advanced yolk granule oocytes in some ovaries, which implies that spawning was imminent. The spawning of P. melbournensis throughout the year contrasts with the far more restricted spawning periods recorded for other teleosts in the same temperate Australian waters. In this respect, P. melbournensis exhibits the characteristics of the essentially tropical family to which it belongs. Annuli, which could be detected on the otoliths of c . 40% of fish, suggest that the majority of P. melbournensis Were <3 years old.