Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50–100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Respiratory protective devices which would protect the wearer against noxious material and gases are not worn in many of the appropriate circumstances. They have been said to feel uncomfortable and hot. In the present study, six men and six women in a 25 degrees C room reported on facial discomfort, thermal sensation, and sweating while wearing three different types of half-facepiece respirators requiring tidal airflow. Skin temperature of the face was measured using a thermocouple taped to the nasolabial fold. The subjects reported that the face felt comfortable when the skin temperature was 34 degrees C or below. However, at skin temperatures above 34.5 degrees C, the face felt increasingly warm, uncomfortable, and sweaty. This finding is similar to that reported previously when subjects wore a half-facepiece respirator supplied continuously with warm, humid air. The conclusion is that thermal conditions of the face contributed to, and may possibly dominate, the discomfort of wearing respiratory protective devices.

"Respiratory myoclonus" may be a heterogeneous disorder ranging from synchronous movements of the diaphragm and other respiratory muscles associated with respiratory compromise, to diaphragmatic movements under at least some volitional control with no respiratory or functional disability. The latter group could be designated phenomenologically as "isolated diaphragmatic tremor."

High skin temperature of the face is a major source of discomfort while wearing respiratory protective devices. In this paper theoretical considerations of thermal exchange between the face and the environment with and without a mask are discussed to elucidate factors that may improve the design of masks to increase their acceptability. Comfort thresholds have been related to skin temperature for both resting and exercising subjects. Skin temperature below 34.5 degrees C at rest, and 31 degrees C during exercise, is rated as comfortable. In a previous study it was determined that evaporative cooling could reduce skin temperature and decrease discomfort in a dummy mask. In the present study evaporative cooling of a more sophisticated dummy mask and a modified Scott model 66 twin-cartridge respirator was tested in resting and exercising subjects. Skin temperature was significantly reduced when wet felt covered the surface of both masks and at rest the masks were rated as significantly more comfortable than with dry felt on the outer surface. It is concluded that evaporative cooling of an existing face mask can reduce skin temperature to the comfort threshold in resting subjects. Data suggest that similar results are attainable for exercising subjects.

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