A simple method to test condoms for penetration by viruses.

A method by which virus penetration through condoms can be tested with simple, inexpensive equipment is described. The method uses chi X174 bacteriophage as the challenge virus and physiologically relevant pressure. Penetration by 0.1 microliters (or less) of challenge suspension can be readily detected. As examples, latex and natural-membrane condoms were examined.     

Insulin binding in the hypothalamus of lean and genetically obese Zucker rats

Recent reports have suggested that the obesity and hyperphagia of the genetically obese Zucker rat may be related to defective insulin action or binding in the hypothalamus. We used quantitative autoradiography to determine if insulin binding is altered in specific hypothalamic nuclei associated with food intake. Insulin binding was measured in the arcuate (ARC), dorsomedial (DMN), and ventromedial (VMN) hypothalamic nuclei of 3–4-month-old lean (Fa/Fa) and genetically obese (fa/fa) Zucker rats. A consistently reproducible 15% increase in the total specific binding of 0.1 nM [¹²⁵I]-insulin was found in the ARC of the obese genotype. A slight increase in insulin binding in the DMN was also found. No difference in specific insulin binding was found between genotypes in the VMN. Nonlinear least squares analysis of competitive binding studies showed that the K_d of the ARC insulin binding site was 33% higher in the lean rats than in the obese rats, indicating an increased affinity for insulin. No difference in site number (B_max) was found in the ARC, DMN or VMN, and no evidence was found for reduced insulin binding in the hypothalamus of the obese (fa/fa) genotype. The results suggest that hyperphagia and obesity of the obese (fa/fa) Zucker rat genotype may be associated with increased insulin binding in the arcuate nucleus.     

Functional expression of dihydropyridine-insensitive calcium channels during PC12 cell differentiation by nerve growth factor (NGF), oncogenic ras,or src tyrosine kinase

1. Recombinant retroviruses were used to introduce a temperature-sensitive v-src gene and oncogenic c-Ha-ras into PC12 cells, and stable cell lines expressing these genes were established. 2. As previously reported, expression of v-src (Alema et al., 1985) or c-Ha-ras (Noda et al., 1985) in PC12 cells results in neurite outgrowth resembling that induced by NGF. We report here that v-src but not oncogenic c-Ha-ras induces a stable morphologic neuronal differentiation similar to treatment with NGF. Oncogenic c-Ha-ras-induced neurite outgrowth is not stable with long-term culture, rather the cells revert to an undifferentiated morphology with altered cell cycle kinetics. 3. The stable neuronal phenotype induced by v-src and NGF is characterized by the functional expression of dihydropyridine-insensitive calcium currents.     

Nasal trigeminal responses to toluene presented by an automated delivery system

An apparatus was developed which permits the automated deliveryof volatile chemical stimuli for use in neurophysiology experiments.A computer-controlled olfactometer, incorporating electronicmass flow controllers (EMFCs) and Teflon-lined solenoid valves,generated and delivered clean or odorized air. Neural and respiratorysignals from the animal were amplified and stored, along withtrial information (e.g. odorant concentration) on a chart recorderand video cassette recorder, both of which were controlled bythe computer. This apparatus was used to measure responses totoluene from the rat ethmoid nerve, a part of the ophthalmicdivision of the trigeminal nerve. Multi-unit responses to thiscompound were first observed at 2000 p.p.m. The magnitude ofthe response increased linearly with logarithmic increases inconcentration up to vapour saturation. Changes in respirationin response to toluene also were observed, although neural responsesoften were seen in the absence of respiratory changes.     

Vulnerability of early life intervals of Coregonus hoyi to predation by a freshwater mysid,Mysis relicta

Synopsis The bloater, Coregonus hoyi, deposits its eggs on deep sediments (70–100 m in Lake Michigan), where its eggs and embryos can be exposed to epibenthic predators. We investigated the vulnerability of early life intervals of bloaters to predation by mysids, Mysis relicta, which are mostly epibenthic by day and planktonic at night. Bloaters were raised from spawn in the laboratory and presented to field-collected mysids in laboratory predation trials. Eggs were not ingested by the mysids. Embryonic bloaters were vulnerable to predation by mysids only during the interval between hatching and swim up, usually 1–24 h under laboratory conditions. The mysids required about a day of exposure to this novel prey before they were able to kill significant numbers of the bloater embryos by making successive attacks with their thoracic legs. In experiments with experienced (2 and 3 days with bloater embryos) mysids, a functional response between embryo density and mysid predation rates was apparent. Temperature and the presence of alternative prey (zooplankton) did not alter the ‘kill rate’ (about 2.5 embryos mysid^-1d^-1) of experienced mysids at high bloater densities (>4 bloaters/mysid). However, more embryos were partially, rather than completely, ingested at 4 versus 9° C and in the presence of zooplankton.     

Age and growth of tarpon,Megalops atlanticus,larvae in the eastern Gulf of Mexico,with notes on relative abundance and probable spawning areas

Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d^–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration.     

Molecular motors in axonal transport

Neurons require a large amount of intracellular transport. Cytoplasmic polypeptides and membrane-bounded organelles move from the perikaryon, down the length of the axon, and to the synaptic terminals. This movement occurs at distinct rates and is termed axonal transport. Axonal transport is divided into the slow transport of cytoplasmic proteins including glycolytic enzymes and cytoskeletal structures and the fast transport of membrane-bounded organelles along linear arrays of microtubules. The polypeptide compositions of the rate classes of axonal transport have been well characterized, but the underlying molecular mechanisms of this movement are less clear. Progress has been particularly slow toward understanding force-generation in slow transport, but recent developments have provided insight into the molecular motors involved in fast axonal transport. Recent advances in the cellular and molecular biology of one fast axonal transport motor, kinesin, have provided a clearer understanding of organelle movement along microtubules. The availability of cellular and molecular probes for kinesin and other putative axonal transport motors have led to a reevaluation of our understanding of intracellular motility.     

Expression of two cytochromes P450 involved in carcinogen activation in a human colon cell line

Cytochrome P450 is known to cause carcinogen activation and correspondingly increased cancer risk in animal models. In order to determine whether P450 in the colon may be involved in cancer development in the human, the human colon cell line LS174T was examined for the presence of various cytochromes P450. Two isozymes of P450 were identified in the human cell line. Expression of P450IAl or IA2 was increased by treatment of the cell line with benzanthracene; the induction was demonstrated by an increase in RNA hybridizing to a probe for P4501Al and by ethoxyresorufin deethylation activity. Western analysis of microsomes isolated from human colon tissue also demonstrated the presence of P4501A1, as well as a form which cross-reacted to an antibody to human P450IIC9. Another isozyme, P450IIE1, was identified by polymerase chain reaction amplification of RNA from LS174T cells. These results underscore the presence of cytochromes P450 in colonic tissue and provide a basis for the involvement of isozyme-specific P450 mediated reactions in carcinogenesis of the colon.Some of the data presented here were taken from a thesis submitted by D.K.H. in partial fulfillment of the requirements for the Ph.D. degree in the University of Texas Graduate School of Biomedical Sciences.     

Differentiation of newborn rat adipocyte precursors in defined serum-free medium

Summary Newborn rat adipocyte precursors, isolated from inguinal fat pads of 2 day-old NBR rats proliferate and undergo adipose differentiation in defined medium in the absence of serum when cultivated on polylysine coated dishes in DME-F12 medium supplemented with fibronectin, insulin, transferrin and FGF. After 7 days in culture in these conditions, 90% of the cells have undergone differentiation as measured by the increase of G3PDH specific activity and by the accumulation of triglycerides in their cytoplasm. In contrast, the cells cultivated in the presence of 10% fetal bovine serum, have a limited ability to differentiate. These results indicate that newborn rat adipocyte precursors from inguinal fat pads do not require the presence of an undefined adipogenic factor in order to differentiate in culture. In contrast, proliferation and differentiation are dependent on the presence of insulin in the culture medium. Moreover, the data presented in this paper show that the rat adipocyte precursor culture represents a rapid and reproducible system for investigating the processes of adipose tissue development and for studying the negative and positive regulators of the adipose differentiation in a controlled environment. This work was supported by grants from the Juvenile Diabetes Foundation, File #185221 and from the National Institutes of Health 1 PO1 CA37589. Editor’s Statement This paper extends to primary cultures the serum-free methods previously applied to studies of adipocyte differentiation in established lines. The observation that serum can block differentiation in this system suggests the existence of previously unrecognized circulating plasma or platelet factors affecting adipocyte differentiation, and the model developed provides an assay for the identification of these factors.     

The delta psi- and Hsp70/MIM44-dependent reaction cycle driving early steps of protein import into mitochondria.

New steps in the reaction cycle that drives protein translocation into the mitochondrial matrix have been defined. The membrane potential (delta psi)- and the mtHsp70/MIM44-dependent import machinery cooperate in the transfer of the presequence across the inner membrane. Translocation intermediates, arrested at a stage where only the presequence could form a complex with mtHsp70, still required delta psi for further import. Delta psi at this stage prevented retrograde movement, since mtHsp70 did not bind to the presequence with sufficient affinity. In contrast, mature regions of incoming chains adjacent to the presequence were bound by mtHsp70 tightly enough to stabilize them in the matrix. Cycling of the mtHsp70 on and off incoming chains is a continuous process in the presence of matrix ATP. Both MIM44-bound and free forms of mtHsp70 were found in association with the incoming chains. These data are consistent with a reaction pathway in which the mtHsp70/MIM44 complex acts as a molecular ratchet on the cis side of the inner membrane to drive protein translocation into the matrix.