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Biomedical subjects

M Hines

Publications and source records attributed to M Hines.

At least 55 records · Page 3Linked to original sources
PubMed1985

Estrogens before birth and development of sex-related reproductive traits in the female guinea pig.

Influences of estrogens on the differentiation of psychosexual traits in the female guinea pig were studied. Pregnant animals were injected intramuscularly with either 1, 2, or 3.3 micrograms estradiol benzoate (EB) or with 1 or 3 micrograms diethylstilbestrol dipropionate (DESDP). Injections were started on the 29th day of pregnancy, given daily for 6 days, and continued every other day until parturition. Female offspring were evaluated for onset of puberty, ovarian function, and lordosis and mounting behavior in adulthood. Prenatal treatment with 3 micrograms DESDP caused delayed puberty, impaired ovarian function, reduced responsiveness of lordosis to EB and P in adulthood (defeminization), augmented mounting in the absence of hormones (masculinization), and reduced responsiveness of mounting to exogenous EB and P in adulthood (defeminization). Prenatal treatment with 1 microgram DESDP produced similar but less pronounced effects. Prenatal treatment with 3.3 micrograms EB also caused a delay in puberty. However, responsiveness of lordosis to EB and P in adulthood was enhanced by treatment with either 1 or 3.3 micrograms EB prenatally. Further, neither mounting in the absence of hormones nor mounting in response to EB and P in adulthood were affected in any measurable way by any prenatal treatment with EB. These results show that estrogens can have masculinizing and defeminizing effects on sexually dimorphic reproductive traits in guinea pigs. The failure of EB to duplicate or parallel the effects of DESDP is not completely understood at this time, but it may indicate that less of the active substance reaches the target tissues following maternal and placental metabolism of EB than of DESDP.

Animals↗
PubMed1985

On the contribution of dynein-like activity to twisting in a three-dimensional sliding filament model.

It has been shown (Hines, M., and J. J. Blum, Biophys.J., 1984, 46:559-565) that passive moment-bearing links do not contribute appreciable twist resistance to an axoneme nor do they cause appreciable twisting in response to internal shear forces. We now examine the contribution of active moment-bearing links such as dynein arms to the generation of twist within an axoneme. The dynein model used causes distal sliding of the adjacent doublet by a force dependent on the angle of attachment of the arms. Attachment of the arms occurs at a specified angle relative to the angle of minimum potential energy. The steady state shape consistent with the forces applied by the attached dyneins is computed. It is shown that the twist generated in an active region is counterclockwise as viewed from tip to base and therefore accumulates at the end of the axoneme. For realistic forces and twist resistances, cumulative twist should not exceed a few degrees.

Adenosine Triphosphatases↗
PubMed1985

Sexually dimorphic regions in the medial preoptic area and the bed nucleus of the stria terminalis of the guinea pig brain: a description and an investigation of their relationship to gonadal steroids in adulthood.

Sexually dimorphic regions are described in two areas of the guinea pig brain: the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST). The volume of a darkly staining portion of the MPOA is approximately 4-fold larger in male than in female guinea pigs, and the volume of a darkly staining portion of the BNST is approximately 36% larger in male than in female animals. The sex differences in both of these areas are present in animals that have been gonadectomized as adults as well as in intact animals, suggesting that they result from differences between the sexes in the hormonal environment during early development. Both the MPOA and the BNST bind high levels of gonadal steroids early in life, during the period when functional differentiation occurs. It is possible that dramatic morphological sex differences characterize such steroid-binding areas. Furthermore, these sexually dimorphic areas may form an anatomically and functionally interrelated system. Attention to these possibilities may help elucidate more precisely the neural basis for sexually dimorphic functions, as well as the basic mechanisms underlying sexual differentiation of behavior and the brain.

Animals↗
PubMed1984

Pre- and postnatal influence of testosterone propionate and diethylstilbestrol on differentiation of the sexually dimorphic nucleus of the preoptic area in male and female rats.

The volume of the sexually dimorphic nucleus in the preoptic area (SDN-POA) of the rat brain is several fold larger in males than in females. When female rats were treated pre- and postnatally with testosterone propionate (TP) or with diethylstilbestrol (DES) they became anovulatory and their SDN-POA developed equivalent in size to that of normal males. Identical treatment of male rats resulted in deficient testicular development, but had no influence on SDN-POA volume. The results indicate that the gross morphological sex difference in SDN-POA volume can exclusively be controlled by the hormonal environment during the critical period of sexual brain differentiation, and that non-steroidal estrogens are just as effective as convertible androgens in stimulating SDN-POA differentiation.

Animals↗
PubMed1984

Compensation for resistance in series with excitable membranes.

Extracellular resistance in series (Rs) with excitable membranes can give rise to significant voltage errors that distort the current records in voltage-clamped membranes. Electrical methods for measurement of and compensation for such resistances are described and evaluated. Measurement of Rs by the conventional voltage jump in response to a current step is accurate but the measurement of sine-wave admittance under voltage-clamp conditions is better, having about a fivefold improvement in resolution (+/- 0.1 omega cm2) over the conventional method. Conventional feedback of the membrane current signal to correct the Rs error signal leads to instability of the voltage clamp when approximately two-thirds of the error is corrected. We describe an active electronic bridge circuit that subtracts membrane capacitance from the total membrane current and allows full, yet stable, compensation for the voltage error due to ionic currents. Furthermore, this method provides not only fast and accurate control of the membrane potential in response to a command step, but also fast recovery following an abrupt change in the membrane conductance. Marked changes in the kinetics and amplitude of ionic currents resulting from full compensation for Rs are shown for several typical potential patterns.

Animals↗
PubMed1984

On the contribution of moment-bearing links to bending and twisting in a three-dimensional sliding filament model.

Previously (Hines, M., and J.J. Blum 1983, Biophys. J., 41:67-79), a method was developed that allowed one to compute curvature and twist for a three-dimensional sliding filament model. In that formalism it was difficult to specify the shear and bending moments arising from moment-bearing interfilament links such as fixed 5-6 bridges or dyneins. Euler's equation offers a straightforward method for computing these bending and shear moments when the potential energy stored in the links as a function of axonemal shape is specified. We used this approach to examine the effect of 5-6 bridges on curvature and twist for several distributions of internal shear moments. Twist changes the angle that a link makes with a doublet and thus in some circumstances may reduce the potential energy stored in those links. Twist is a second-order effect proportional to the square of the distance between an outer doublet and the neutral axis. Fixed links will not generate twist if they are symmetrically located around the axoneme.

Animals↗
PubMed1983

Three-dimensional mechanics of eukaryotic flagella.

Equations are derived that account for the contribution of internal structure of cilia and flagella to motion in three dimensions according to a sliding filament model of the motile system. It is shown that for reasonable amounts of bending and twisting, the bending properties of an axoneme can be described by a linear elastic bending resistance, and approximate values for the bending and twisting resistances are computed. Expressions for the shear moments contributed by purely elastic or pinned links between filaments are also derived. It is shown that within the confines of a strict sliding filament model such internal structures cannot by themselves produce twist. Thus planar bending will occur if the internal shear force lies in a plane. Application of an external force, however, will in general produce twisting. Computer simulations of flagellar shape in response to a constant external force applied to the distal end of the axoneme are presented. It is shown that a small amount of twist may arise because of acylindrical bend resistance. Large twists, however, result when the external force is applied to an axoneme with internal shear resistant links.

Animals↗
PubMed1983

Sports medicine.

Explore the source record for details and available documents.

Health Promotion↗
PubMed1982

Differentiation of the sexually dimorphic nucleus in the preoptic area of the rat brain is determined by the perinatal hormone environment.

The volume of a sexually dimorphic nucleus in the preoptic area (SDN-POA) of the rat brain is several fold larger in males than in females. When female rats were treated pre- and postnatally with testosterone propionate (TP) their SDN-POA developed equivalent in size to that of normal males. The results indicate that the gross morphological sex difference in SDN-POA volume is exclusively controlled by the hormonal environment during the critical period of sexual brain differentiation.

Animals↗
PubMed1982

Behavioral definitions of problem drinking among college students.

Four hundred college students rated the extent to which 53 behaviors and situations were indicative of problem drinking, yielding 6 factors. Significant differences were found between men and women on 4 factors and among quantity-frequency drinking categories on all 6 factors.

Adult↗
PubMed1980

Modified snake venom in amyotrophic lateral sclerosis. Lack of clinical effectiveness.

Diverse observations including neurological examination, manual muscle testing, quantitative electromyography, videotape esophagrams, and pulmonary function tests were used in a double-blind study evaluating the use of detoxified snake venoms as modified neurotoxin in 64 patients with amyotrophic lateral sclerosis (ALS) treated for six months. Transient periods of improvement were more common in the patients who received placebo. This study did not demonstrate any benefit from administration of modified snake venom to patients with ALS.

Amyotrophic Lateral Sclerosis↗
PubMed1979

Bend propagation in flagella. II. Incorporation of dynein cross-bridge kinetics into the equations of motion.

The cross-bridge formalism of T. Hill has been incorporated into the nonlinear differential equations describing planar flagellar motion in an external viscous medium. A stable numerical procedure for solution of these equations is presented. A self-consistent two-state diagram with curvature-dependent rate functions is sufficient to generate stable propagating waves with frequencies and amplitudes typical of sperm flagella. For a particular choice of attachment and detachment rate functions, reasonable variation of frequency and wave speed with increasing viscosity is also obtained. The method can easily be extended to study more realistic state diagrams.

Adenosine Triphosphatases↗