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In the sea urchin embryo, the micromeres act as a vegetal signaling center. These cells have been shown to induce endoderm; however, their role in mesoderm development has been less clear. We demonstrate that the micromeres play an important role in the induction of secondary mesenchyme cells (SMCs), possibly by activating the Notch signaling pathway. After removing the micromeres, we observed a significant delay in the formation of all mesodermal cell types examined. In addition, there was a marked reduction in the numbers of pigment cells, blastocoelar cells and cells expressing the SMC1 antigen, a marker for prospective SMCs. The development of skeletogenic cells and muscle cells, however, was not severely affected. Transplantation of micromeres to animal cells resulted in the induction of SMC1-positive cells, pigment cells, blastocoelar cells and muscle cells. The numbers of these cell types were less than those found in sham transplantation control embryos, suggesting that animal cells are less responsive to the micromere-derived signal than vegetal cells. Previous studies have demonstrated a role for Notch signaling in the development of SMCs. We show that the micromere-derived signal is necessary for the downregulation of the Notch protein, which is correlated with its activation, in prospective SMCs. We propose that the micromeres induce adjacent cells to form SMCs, possibly by presenting a ligand for the Notch receptor.

In the embryos of the gastropod Ilyanassa obsoleta, the development of several ectodermal structures requires an inductive interaction between the micromeres and the D macromere. The first quartet micromeres (1a, 1b, 1c and 1d) contribute to the head of the larva and descendants of 1a and 1c normally develop the eyes. The eyes do not develop if 1a and 1c are removed at the eight-cell stage. However, regulative eye development may occur if the precursors of 1a and 1c are removed at the two- or four-cell stage. One purpose of this study was to demonstrate which cells of the cleavage-stage embryo have the potential to develop an eye. The results of blastomere deletion experiments suggest that only the first quartet micromeres have this ability. In addition, the 1b micromere was found to be equivalent to 1a and 1c, but 1d was found to have a poorer eye-forming ability. A second purpose of this study was to examine how eye development is normally restricted to the 1a and 1c micromeres. Cell transplantation experiments demonstrate that the proximity of a first quartet micromere relative to the inducing D macromere is important for determining whether or not it will go on to develop an eye. The 1b micromere may not develop an eye during normal development because it is too far from the D macromere. However, the eye-forming ability of the 1d micromere is not influenced by its close position to the D macromere, but is restricted by its polar lobe lineage.

Gray tremor (gt) is an autosomal recessive mutation in the mouse linked to caracul (Ca) on chromosome 15. The complex mutant phenotype includes pigmentation defects, tremor, seizures, hypo- and dysmyelination in central and peripheral nervous systems, spongiform encephalopathy, and early death. The heterozygote (+/gt) is phenotypically normal but develops a mild spongiform encephalopathy from 2 months of age onward. The pigmentation and myelination disorders indicate that the gt genetic locus is active neonatally and probably earlier. This report focuses mainly on the later-expressed vacuolating disorder, which most closely mimics in tissue distribution, histopathology, and ultrastructure the spongiform encephalopathies caused by unconventional transmissible agents. This lesion was produced in genetically normal mice in a transmission experiment: of 99 neonatal mice inoculated intracerebrally with gt/gt brain homogenate, all 7 mice of three strains (BALB/cBy, C3HeB/FeJ, and C57BL/6J) allowed to survive for the unusually long interval of 682-721 days after inoculation, developed spongiform changes distributed as in the mutant phenotype. The gray tremor mutant presents a naturally occurring spongiform encephalopathy whose expression is determined by the interaction of genetic factors and a transmissible agent.

An autosomal recessive mutation, termed fatty liver dystrophy (fld), can be identified in neonatal mice by their enlarged and fatty liver (Sweet, H. O., Birkenmeier, E. H., and Davisson, M. T. (1988) Mouse News Letter81, 69). We have examined the underlying metabolic abnormalities in fld/fldmice from postnatal days 3–40. Serum and hepatic triglyceride levels were elevated 5-fold in suckling fld/fldmice compared to their +/? littermates but abruptly resolved at the suckling/weaning transition. Blot hybridization analysis of liver and intestinal RNAs revealed a liver-specific increase in apolipoprotein (apo) A-IV and C-II mRNA concentrations (100- and 6-fold, respectively) that was limited to the suckling and early weaning stages in fld/fldmice. Resolution of these differences during the weaning period could not be delayed by prolonging suckling to the 20th postnatal day nor could the mutant phenotype be elicited in young adult animals with a high fat diet. Lipoprotein lipase (LPL) activity was reduced 16-fold in the white adipose tissue of fld/fldmice until the onset of weaning. Heart activity was decreased <2-fold, but there were no deficits in brown adipose tissue or liver. Hepatic lipase (HL) mRNA levels and activity were significantly reduced in fld/fldlivers and sera, respectively, during the suckling period. Mapping studies show the fldlocus to be distinct from loci encoding LPL, HL, and apoA-IV, and those responsible for the combined lipase deficiencies in cld/cldand W/Wvmice. These data suggest that the fldmutation is associated with developmentally programmed tissue-specific defects in the neonatal expression of LPL and HL activities and provide evidence for a new regulatory locus which affects these lipase activities. This mutation could serve as a useful model for (i) analyzing the homeostatic mechanisms controlling lipid metabolism in newborn mice and (ii) understanding and treating certain inborn errors in human triglyceride metabolism.

Observes the growing popularity of sports activities on the beach. Windsurfing; Riding a catamaran; Surfing; Swimming; Volleyball; Power walking in the sand; Triathlons; Why beach games are both enjoyable and healthy; Tips on how to exercise at the beach. INSET: Dream tan, by H.S..

Presents highlights of recent scientific studies on the benefits of water. Importance of water in skin care; Replacing water lost every day; Recommendations for water consumption; Growing concerns about water supplies.

Lists several inexpensive beauty treatments nationwide. Quick Service hair salons; Attending class/trainee nights at local hair salons; Cost savers in major cities; Skincare expert Adrien Arpel's tips for saving on makeup and treatment; Beauty experts' makeup tricks; Inexpensive products used by celebrities.

Offers tips for minimal summer beauty regimens that won't sacrifice good looks. Fragrances; Make-up; Skin care; Hair care and styling.

Provides a 45-minute workout for women by trainer Stephanie Herman. Focus on hitting virtually every muscle group; Combining the leg and body-elongating effects of ballet with the stamina-building of aerobics and strength work; How to approach the workout.

Surveys the offerings of anti-aging spas around the world. Ozone, light and laser, and radioactive water therapies popular in Europe; Cell therapy; Cosmetic surgery; Relaxation; Therapeutic baths; Emphasis on the regeneration and relaxing properties of water; Preventive techniques in the US; Popular spots noted, such as Clinique La Prairie, in Montreux, Switzerland, Baden-Baden in Germany, The Pritikin Longevity Center, in Santa Monica and Miami and more.

Advises women over age 40 on innovative ways to preserve their skin. Natural growth hormones; Vitamin C update; Sun protection; New-Age fruit peels; Cosmeceutical breakthroughs; Erasing dark circles under the eyes; Reducing stress on skin; Age-deflecting creams called `skin brighteners.'

Observes a growing trend toward specificity among body fitness experts. Emphasis on precisely focused effort performed with correct form in sufficient quantity; Choosing the right sports and exercise to tone specific areas of the body.

Surveys a variety of liquid diet plans that have been or continue to be popular in America. Skim milk and bananas; Dr. Stoll's Diet-Aid; Breast-milk imitation developed by Rockefeller Institute researchers; `Lockjaw' dieting; Last Chance Diet; Cambridge Diet; More. INSET: Medically monitered fasts, by H.S..

Highlights the book `The Strength Connection,' by the Institute for Aerobics Research. New emphasis on the concept of balanced fitness; How it works.

Discusses ongoing research on sunscreen. Limitations of the current SPF rating system; Studies on sunscreen's pre-sunburn effectiveness; New sunscreen technology for future products.

Presents highlights of a recent study on the benefit of ten-minute exercises. Research conducted; Concept of `less is more'; Suggested short and simple exercise routines.

Presents an update of new information on personal health. Skin-safe computer screens; Healthier fast food; Weight-gain age gap for women; Effects of exercise on cholesterol levels; `Soft' weight training.

Presents an account of one woman's successful attempt to quit smoking cigarettes. Supportive approach; Withdrawal symptoms.

Profiles Olympic swimmer Dara Torres. Past medals won in relay competitions; Dreams of winning a medal in the 100-meter freestyle; Decision to take a two-year break from swimming; How she set the U.S. Open record in the 100-meter freestyle just 20 weeks into her comeback.

Profiles urban planner and project manager Kimberly Beasley of Allee, King, Rosen & Flemming Inc., New York City-based enviornmental and planning consultants. Background; How she works to keep New York City development enviornmentally sound.

Comments on the way women's skin changes during the dry season of winter. How skin is affected as vital humidity from the summer drains from the air; Efforts to retain moisture; Research conducted on winter-parched skin tissues; Moisturizing benefits.

Forecasts new hair trends for 1991. How salons and stylists will change; New emphasis on hair treatments; Environmentally friendly hair products; Predicted springtime hair fashions.

A look at moving through water: the hot new fitness trend. Examines its positive features and its drawbacks.

A look at today's gyms and how the competitive fitness business has encouraged them to become more service-oriented. Amenities; Locations; Facilities.

Discusses the sports shoe industry. Beyond athletic appeal, sneakers are showing up away from the gym. Cycling; Trekking; Walking; And nonathletic endeavors.